American Racing AR23 Wheels and Rims – Equipping Your Vehicle to the New Era of Urban Style

American Racing AR23 Wheels and Rims – Equipping Your Vehicle to the New Era of Urban Style

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Car Shipping Will Help You To Have Your Vehicle Shipped

Car Shipping Will Help You To Have Your Vehicle Shipped
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More Radical Transparency Articles

Pressurized Vehicle

Pressurized Vehicle

Some of the big engineering challenges and safety problems to manned exploration of The Moon and Mars, are that spacesuits have to be pressurized, and this makes it difficult for astronauts to bend knees, elbows and fingers, causing them to get fatigued quickly. Radiation and dust contamination for the crew is a major health risk and spacesuit failure from rips, meteors, and cracks are fatal.

In this concept we have my pressurized vehicle that could transport explorers over long distances and harsh landscapes, like an ant on roller skates, each of the six legs can move independently, with a full range of movement over and around large obstacles and adjusting for inclination as needed. The astronaut would egress from the roof of the crew cabin into the bucket via an airlock in the floor of the bucket. Then like a cherry picker, the astronaut would move the bucket into the spot the astronaut wanted to be in, up high on a cliff or face down on the deck and they will look at samples closeup with their own eyes, then using the robotic arms for collecting the samples. The robotic hands could be changed out with different tools on the fly. Drill, hammer, saw, chisel, ratchet, and so on.

The vehicle, bucket and arms, could be operated remotely from the crew cab, from a geosynchronous orbit, or from choreographed computer command lines.

This vehicle would be powered hydrogen fuel cells that can be recharged infinitely by photovoltaic solar cells.

Posted by boston7513 Kevin Moore on 2011-03-10 22:17:15

Tagged: , spacesuits , The Moon , Mars , vehicle , astronauts , explorers , transport , robotic arms , blender 2.56a , Moon Landing , collecting samples , moonraker , moon buggy , Luner x Prize , Luner , XPrize , Moon Base

Aqeri 31002

Aqeri 31002

Aqeri 31002 is our latest High Performance vehicle and industry computer with an Intel® Mobile Core2Duo processor. The computer is specially designed to withstand the rough treatment a computer usually is exposed to in vehicles and heavy industry worldwide. It is resistant to elements as dust, shocks, vibrations, moist, strong heat and cold. It has built in intelligent against spikes, reversed polarity, function for remote on/off and safe shutdown. The computer has a climate control for heating and cooling and warning system for over heat and under cold.

Features:
> Fanless mulitfunctional computer with expansion possiblities
> Designed for vehicle and industry use
> Extended temperature range -20 to +55 degrees operating
> Designed for harsh environments
> Small form factor

Testing

Aqeri official home

Posted by Aqeri on 2010-10-27 19:51:31

Tagged: , Computer , Aqeri , fanless , vehicle , industry , Core , 2 , Duo , 2.66GHz , PCQT , PROPAC , Sweden , 2010 , Scanautomatic , VGA , HDMI , COM , DVI

Die Ernte / The Harvest

Die Ernte / The Harvest

Ein Mähdrescher ist eine landwirtschaftliche Erntemaschine zur Ernte von Körnerfrüchten wie insbesondere Getreide, aber auch Raps, Sonnenblumen, Ackerbohnen, Grassamen oder Ähnlichem. Wie die zusammengesetzte Bezeichnung (vgl. auch im Englischen: combine harvester) andeutet, kann der Mähdrescher mehrere Verfahrensschritte in einem Arbeitsgang erledigen, insbesondere die Mahd und den Drusch der Körnerfrüchte.

Vorne am Mähdrescher ist das Schneidwerk oder ein Erntevorsatz angebaut. Diese nehmen das Erntegut vom Feld auf, ein Schneidwerk übernimmt überdies die Aufgabe des Mähens. Je nach Art der Druschfrüchte kommen verschiedene Schneidwerke zum Einsatz.

Da heutige Arbeitsbreiten die auf öffentlichen Straßen maximal zulässige Breite von drei bis dreieinhalb Meter meist übersteigen (Arbeitsbreiten von fast 14 Meter für Getreide und 12 Meter für Mais sind möglich), kann das Schneidwerk für Straßenfahrt entweder abgebaut oder (hydraulisch) zusammengeklappt werden. Das abgebaute Schneidwerk wird mit einem Schneidwerkswagen transportiert, welcher entweder vom Mähdrescher selbst oder einem anderen Zugfahrzeug gezogen wird.

Ein Schneidwerk besteht aus dem Schneidtisch sowie Halmteilern, welche die Getreidehalme der zu mähenden Bahn von dem noch stehen bleibenden Getreide abteilen, ggfls. Ährenhebern, welche liegende Getreidehalme (Lagergetreide) unterfahren und aufrichten sollen, der der Zuführung der Getreidehalme zum Mähwerk dienenden Haspel[1], dem Fingermähwerk und der Einzugsschnecke bzw. dem Förderband, welche das Schnittgut dem Dreschwerk zuführen.
Bei der Ernte von Raps werden zur Trennung der Schnittbahnen an den Seiten des Schneidwerkes seitlich senkrecht stehende Scherenschnittmesser angebaut und der Schneidtisch wird verlängert. Raps fällt sehr leicht aus den Samenständen heraus, und die sich verzweigenden Einzelpflanzen verhaken sich miteinander. Durch ein Auseinanderreißen der untereinander verworrenen Rapspflanzen würde es zu erheblichen Kornverlusten kommen. Die Verlängerung fängt die Samen auf, die von der Haspel ausgeschlagen werden.

Maispflücker oder Maisgebisse sind so konzipiert, dass die Pflanzenstängel bei der Überfahrt durch einen schmal zulaufenden Spalt gezogen und nur die dabei abgepflückten Kolben dem Dreschwerk zugeführt werden, während ein unter dem Tisch angebrachtes Häckselwerk die Reste zerkleinert. Für Getreide gibt es außerdem Ährenstripper oder auch nur Stripper genannt. Diese arbeiten nach demselben Prinzip wie Maispflücker. Von Vorteil ist, dass das Stroh nicht durch die Maschine muss, und sich somit die Stundenleistung des Mähdreschers erhöht.

Beim Drusch von Sonnenblumen werden die Blütenstände vom Stängel getrennt. Vom Aufbau ähneln Sonnenblumenschneidwerke den Maisschneidwerken.

Bei ungleichmäßig abreifenden Beständen wird die Frucht zunächst mit einem Schwadmäher abgemäht und auf Schwad abgelegt. Nach weiterem Abreifen der Frucht im Schwad nimmt der Mähdrescher diese mit einer Pick-Up zum Drusch auf.

Der Schrägförderer trägt den Erntevorsatz. Innen läuft eine Einzugskette, die das Erntegut von der Einzugsschnecke übernimmt und es dem Dreschaggregat zuführt.

Unmittelbar am Ende des Schrägförderers befindet sich eine Steinfangmulde. Die Dreschtrommel soll die schwereren Steine dort hineindrücken. Da Rotormähdrescher besonders empfindlich auf eingezogene Steine reagieren, gibt es Systeme, bei dem die Steine durch Klopfsensoren erkannt werden und sich bei Steinerkennung der Boden des Schrägförderers öffnet, so dass der Stein wieder auf den Boden gelangen kann.
Das Dreschorgan besteht aus einem Dreschkorb, in dem sich entweder eine Dreschtrommel oder ein Rotor mit hoher Geschwindigkeit drehen. Der Spalt zwischen Trommel/Rotor und Korb ist sehr eng. So wird das Korn aus dem Stroh ausgerieben und fällt durch die Maschen des Korbes. Etwa 90 % der Körner werden durch das Dreschaggregat vom Stroh getrennt und gelangen direkt in die Reinigung, lediglich das Stroh und darin noch enthaltenes Restkorn gelangen zur Abscheidung. Je nach Art der zu dreschenden Frucht kann über die Variation der Trommeldrehzahl und eine Veränderung des Dreschspaltes zwischen Dreschtrommel und Dreschkorb die Intensität des Druschs variiert werden.

Noch intensiver dreschen kann man durch verschließen der ersten Korbreihen, oder durch den Einbau von Reibleisten. Das ist notwendig, wenn Grannen von Gerstenkörnern abgebrochen werden sollen oder wenn Früchte gedroschen werden, bei denen die Samen sehr fest in den Blütenständen sitzen. Die Abscheidefläche des Korbes verringert sich dabei.

Vom Dreschaggregat gelangt das Erntegut zur Abscheidung, wo die restlichen Körner und nicht vollständig ausgedroschene Ähren vom Stroh getrennt werden. Die Abscheidung erfolgt meist über einen sogenannten Hordenschüttler. Dieser besteht aus mehreren versetzt an einer Kurbelwelle befestigten ca. 20 cm breiten sägezahnförmigen Rinnen, über die das Gut aufgrund der Schüttelbewegung nach hinten wandert, wobei das leichtere und sehr viel größere Stroh den ansteigend verlaufenden Schüttlern folgt. Die Körner und nicht vollständig ausgedroschene Ähren werden vom Stroh getrennt und fallen durch kleine Löcher in den Horden auf das Reinigungssieb. Bei axialen Abscheideorganen erfolgt die Abscheidung an einem oder zwei Rotoren, deren Funktionsweise einem Separator ähnelt. Unterhalb der Rotoren ist ein Korb (ähnlich dem Dreschkorb) angebracht, der das Stroh führt, bis es vom Rotor nach hinten aus dem Mähdrescher oder auf den Häcksler gelangt.

Das Reinigungsgut, bestehend aus Körnern und NKB (Nicht-Korn-Bestandteile = Spreu und Strohteile), gelangt vom Dreschwerk und weiteren Abscheideorganen (Schüttler oder Abscheiderotoren) zur Reinigung. Die Reinigung dieses Gemisches erfolgt in der Regel über zwei übereinander angeordnete Siebe, das Ober- und das Untersieb. Die Zuführung des Reinigungsgutes zu den Sieben erfolgt je nach Hersteller unterschiedlich:
a) Über einen Stufenboden (treppenförmiges Profilblech), der sowohl für die Förderung, als auch für eine gleichmäßige Verteilung in Längs- und Querrichtung und eine gewisse Vorentmischung zuständig ist. b) Über eine aktive Förderung mittels mehreren nebeneinander liegenden Schnecken, deren Hauptaufgabe darin besteht, innerhalb der Reinigung an Höhe zu gewinnen und das Reinigungsgut gleichmäßig den Sieben zuzuführen. c) Eine oder mehrere, mit Hilfe eines Gebläses, belüftete Fallstufen, die bereits vor Erreichen der Siebe einen großen Anteil der leichten Spreuanteile aus dem Reinigungsgut ausblasen. Damit wird vor allem erreicht, dass die Körner unter den NKB auf die Siebfläche auftreffen und zügig abgeschieden werden.

Beide Siebe werden von unten durch einen Luftstrom (Wind) belüftet. Dies sorgt für eine Auflockerung des Reinigungsgutes, wobei im günstigsten Fall eine so genannte Wirbelschichtphase entsteht. Dabei "schwimmen" leichte Anteile wie die Spreu und Kurzstroh auf und ermöglichen den wesentlich schwereren Körnern das Erreichen der Siebfläche.

Das Reinigungsgut gelangt von der Zuführung aus zunächst auf das Obersieb. Dieses hat im Wesentlichen die Aufgabe, Körner und unausgedroschene Ährenteile (Überkehr) zum Untersieb abzuscheiden und die NKB über das Siebende aus dem Mähdrescher zu fördern. Das Untersieb stellt die letzte Reinigungsstufe dar, wobei im Idealfall eine Kornreinheit von über 99,6 % erreicht wird. Das Reinkorn wird über eine Schnecke zu einer Maschinenseite (in der Regel in Fahrtrichtung rechts) und von dort mittels eines Elevators in den Korntank gefördert. Der Siebübergang des Untersiebes (Überkehr) besteht aus unausgedroschenen Ährenteilen, Körnern und Spreu. Diese Überkehr wird mit einer Schnecke zu einer oder beiden Seiten des Mähdreschers gefördert und von dort mit Hilfe einer weiteren Schnecke oder eines Elevators zum Dreschwerk oder den Förderelementen der Reinigung zurückgefördert. Hersteller, die die Überkehr zur Reinigung zurückführen, bauen auf dem Weg dorthin ein zusätzliches kleines Dreschorgan ein.

Da mit den NKB auch große Mengen an Unkrautsamen aus dem Mähdrescher gelangen, wird die Spreu ebenso wie das Stroh (sofern gehäckselt) bei Schnittbreiten über 3 Meter möglichst über die gesamte Arbeitsbreite verteilt, beispielsweise mittels scheibenförmiger Spreuverteiler. Durch Wechsel von Ober- und Untersiebbauarten sowie durch Variation der Windgeschwindigkeiten kann die Reinigung auf die zu dreschende Getreideart eingestellt werden. Sowohl die Frequenz als auch die Amplitude der Siebschwingung werden meist vom Hersteller vorgegeben und können nur mit großem Umbauaufwand geändert werden.

Der Getreidetank dient als Vorratsbehälter für das Korn und wird, oftmals auch parallel zum Drusch, über das Abtankrohr auf einen Transportanhänger oder einen Überladewagen entladen. Das Fassungsvermögen des Korntankes beträgt je nach Größe des Mähdreschers zwischen 5 und 12 Kubikmetern. Er ist im Allgemeinen so bemessen, dass im Getreide 15-30 min lang ohne Entleerung des Tanks gedroschen werden kann.

Am hinteren Ende des Mähdreschers, hinter den Dresch- und Abscheideorganen, wird das gedroschene Stroh aus dem Mähdrescher ausgeworfen. Das Stroh kann entweder zur späteren Bergung mit einer Ballenpresse auf Schwad gelegt oder gehäckselt werden. Zur Schwadablage verfügen Mähdrescher vielfach über Leitbleche oder Zinken, mit denen sich die Schwadbreite verstellen lässt, um diese auf die Presse anzupassen. Häufig ist bei neueren Maschinen ein Strohhäcksler montiert, der das gedroschene Stroh klein häckselt und es über die gesamte Schnittbreite verteilt. Das gehäckselte Stroh kann später in den Boden eingearbeitet werden und trägt so zur Erhöhung des Humusanteils bei. Bei immer größeren Schnittbreiten stellt eine gleichmäßige Strohverteilung heute eine große Herausforderung für die Hersteller dar.

Mit einer Nennleistung von 435 Kilowatt (591 PS) gilt der New Holland CR 9090[3] derzeit als der Mähdrescher mit der höchsten Motorleistung. Moderne Mähdrescher benötigen die Leistung vor allem für das Dreschaggregat, die Abscheideorgane und den Strohhäcksler. Abhängig von den Erntebedingungen und der Arbeitsbreite verbraucht alleine der Häcksler bis zu 20 % der verfügbaren Leistung. Da während des Dreschens sehr viel Staub entsteht, ist die Zuführung der Verbrennungs- und Kühlluft des Motors problembehaftet. Luftfilter und Kühler müssen daher durch maschinelle Einrichtungen sauber gehalten werden, was entweder mittels einer Absaugung, rotierender Bürsten oder durch ein Lüfterwendegetriebe geschieht. Das Wendegetriebe verändert die Drehrichtung des Kühlerventilators ab einer bestimmten Temperatur, so dass dieser den Kühler frei bläst.

Die ganze Maschine sitzt auf einem Fahrwerk, das von zwei großen und breiten Rädern (oft mehr als 80 cm breit) direkt hinter dem Schneidwerk und unterhalb der Kabine dominiert wird. Gelenkt wird über die hinteren, kleineren Räder. Beim Einsatz in schwierigem Gelände kommen Allradantriebe und auch vermehrt Raupenlaufwerke zum Einsatz, deren Vorteile zum einen in einer geringeren Bodenverdichtung und zum anderen in einer höheren Laufruhe der Maschine liegen, die besonders bei sehr breiten Schneidwerken von Bedeutung ist. Durch die Auslegung eines Mähdreschers als Hecklenker kann mit dem unmittelbar vor der Vorderachse montierten Schneidwerk ein sehr enger Wendekreis erreicht werden.

Da die optimale Fahrgeschwindigkeit beim Dreschen von vielen Faktoren abhängt (Motorleistung, Dreschverluste, Bestandsdichte, Lagergetreide, Bodenunebenheiten, etc.), ist es wichtig, dass die Geschwindigkeit des Mähdreschers stufenlos verändert werden kann. Dazu dienen meist Variator- oder hydrostatische Getriebe.

Anstelle des bei frühen Mähdreschern gängigen offenen Fahrerplatzes direkt hinter dem Schneidwerk und über dem Schrägförderer mit erheblicher Staub-, Lärm- und bei entsprechender Witterung Hitzebelastung des Maschinenführers ist bei modernen Mähdreschern fast ausnahmslos an gleicher Stelle eine geschlossene Fahrerkabine aufgebaut. Diese erlaubt einen wirksamen Schutz des Fahrers vor Staub, Lärm und Hitze und ist daher in der Regel klimatisiert und komfortabel für einen langen Arbeitstag (meist zwischen 10 und 14 Stunden) ausgeführt. Sie enthält auch die elektronischen Steuerungen und Anzeigen zur Einstellung und Überwachung aller relevanten Parameter des Mähdreschers (Motoranzeigen, Steuerung des Schneidwerks und des Dreschwerks, immer öfter Instrumente zur Ertragsmessung, teilweise kombiniert mit GPS-Erfassungssystemen).

Die Steuerung des Schneidwerks, des Abtankrohrs und der Fahrgeschwindigkeit wird mit einem Hebel durchgeführt, welcher ständig in der rechten Hand des Fahrers geführt wird (die linke Hand liegt am Lenkradknauf). Bei modernen Mähdreschern ist dies ein Joystick, der die Elektronik ansteuert. In älteren Modellen ist ein Hebel mit den Hydrauliksteuergeräten mechanisch verbunden. Durch Wahl der Hebelgasse wird die Funktion des Steuergeräts (Schneidwerkshöhe, Abstand Haspel/Schneidwerkstisch, Fahrgeschwindigkeit) gewählt. Weitere Hebelgassen können beispielsweise für Haspelgeschwindigkeit oder Dreschtrommeldrehzahl vorhanden sein, sind meist aber erst nach Lösen einer Sicherung zugänglich, um versehentliches Verstellen zu verhindern.

In den letzten Jahren werden vermehrt Steuerungs- und Kontrollaufgaben, die früher durch den Fahrer ausgeführt wurden, von automatisierten Einrichtungen übernommen. So wird beispielsweise das Schneidwerk auf einer vom Fahrer vorgegebenen Schnitthöhe automatisch den Geländeunebenheiten nachgeführt. Sensoren erfassen die Bodenunebenheiten, entsprechend der Sensordaten verändert die automatisierte Steuerung sodann Arbeitshöhe sowie Neigung des Schneidwerks. Ein weiterer Automatisierungsschritt sind selbsttätige Lenksysteme. Durch DGPS kann die Position des Mähdreschers auf dem Feld mit einer Genauigkeit von ± 10 cm bestimmt werden. Mit diesen Informationen führt der Bordcomputer den Mähdrescher parallel entlang der vorherigen Fahrspur über das Feld. Der Fahrer braucht das Steuer nur noch am Ende des Feldes in die Hände zu nehmen, um die Maschine zu wenden. Des Weiteren gibt es Systeme, die mit Sensoren die Menge des Dreschgutes messen und die Geschwindigkeit des Mähdreschers so anpassen, dass dieser immer mit optimaler Auslastung fährt.

Bis zur Mechanisierung der Landwirtschaft wurde Getreide manuell in mehreren Arbeitsschritten geerntet. Zuerst mähte man das Getreide mit Sichel, Sichte oder Sense ab und band es in der Regel zu Garben die man dann zunächst auf dem Feld stehen ließ. Diese Mahd erfolgte bereits vor der beim Mähdrusch erforderlichen Totreife des Getreides, das auf dem Feld in Garben aufgestellte Erntegut konnte auf diesem noch nachreifen und trocknen, sodass bei der Mahd weder Korn noch Stroh die notwendige Trockenheit zur Endlagerung haben mussten. In der Regel transportierte man die Garben sodann zum Bauernhof, dort wurde das Getreide, oft nach weiterer Lagerung in der Scheune auf der Tenne mit Dreschflegeln ausgedroschen. Anschließend reinigte man es durch sieben oder worfeln von der Spreu und Verunreinigungen wie Erde oder Unkrautsamen. Beim Worfeln wurden leichte Bestandteile des hochgeworfenen Druschguts wie die Spreu vom Wind weggeweht. Später wurden hierzu einfache handbetriebene Windfegen verwendet, bei denen ein Siebkasten das Getreide in einen darunter angebrachten Windkasten rieseln ließ; diese Windsichtung ist bis heute Bestandteil der Reinigungsstufe von Mähdreschern.

Mit der einsetzenden Mechanisierung wurden etwa ab 1786 zunächst stationäre Dreschmaschinen entwickelt, die Anfangs nur per Hand oder über Göpel durch Tiere angetrieben wurden. Später wurden Dampfmaschinen, Verbrennungsmotoren, Elektromotoren und andere Antriebe eingesetzt. Die erste Mähmaschine für Getreide wurde 1826 von dem schottischen Geistlichen Reverend Patrick Bell entwickelt. Mit der Erfindung des mechanischen Knoters 1857 wurde es möglich, Mähbinder zu bauen, die das Getreide vollmechanisiert zu Garben banden. Zunächst wurden diese Maschinen von Pferden gezogen und dabei über die Maschinenräder angetrieben. Mit Erscheinen brauchbarer Traktoren nutze man zunächst auch diese anstelle von Pferden zum Zug. Erst 1927 produzierte Krupp einen ersten Mähbinder, der unmittelbar über eine Zapfwelle vom Motor des Traktors angetrieben wurde.[4]

Aus der Kombination von Mähmaschine und fahrbarer Dreschmaschine entstanden die ebenfalls mobilen Mähdrescher. Bereits 1834 demonstrierten Hiram Moore und James Hascall in Michigan eine Maschine, die sowohl mähen und dreschen als auch reinigen konnte, die Arbeitsbreite betrug 4,60 Meter.[5] 1836 wurde ihre Maschine patentiert. Bis zu 40 Maultiere oder Pferde waren erforderlich, um diese Maschinen zu ziehen. Der Antrieb der Dresch- und Reinigungsorgane fand über eines der Räder statt. George Stockton Berry baute 1886 den ersten selbstfahrenden Mähdrescher, der von einer Dampfmaschine angetrieben wurde. Der Kessel wurde mit dem ausgedroschenen Stroh befeuert und versorgte auch den separaten Antrieb der Dreschorgane mit Dampf.[6] 1911 verwendete die Holt Manufacturing Company in Stockton, Kalifornien erstmal Verbrennungsmotoren auf Mähdreschern, diese trieben jedoch nur Dresch-, Abscheide- und Reinigungssystem an, und dienten noch nicht als Fahrantrieb.

Der erste selbstfahrende Mähdrescher eines deutschen Herstellers war der MD 1 der Maschinenfabrik Fahr, er wurde auf der DLG-Ausstellung in Hamburg im Jahr 1951 erstmals der Landwirtschaft präsentiert. Ein erster Rotormähdrescher wurde von New Holland im Jahr 1975 auf den Markt gebracht.
Bei der Abscheidung unterscheidet man zwischen zwei grundsätzlich verschiedenen Arten von Abscheideorganen.

Hordenschüttler: Bei herkömmlichen Mähdreschern erfolgt die Abscheidung über einen Hordenschüttler. Der Schüttler besteht aus vier bis sechs Horden, auf deren Oberseite widerhakenförmige Zacken angebracht sind. Alle Horden sind an zwei Kurbelwellen befestigt, die sich drehen. Es ergibt sich eine kreisförmige Exzenterbewegung der Horde: zuerst nach oben, dann nach hinten, dann nach unten, dann nach vorne. Wenn eine Horde am obersten Punkt ist, sind die daneben liegenden Horden am tiefsten. Auf dem Weg nach oben übernehmen die Horden so die Strohmatte von den daneben liegenden und führen sie mit den Widerhaken nach hinten. Bei der Abwärtsbewegung geben sie die Matte wieder an die daneben liegenden Horden ab. Leer laufen sie wieder in Fahrtrichtung nach vorne.
Dadurch wird das Stroh so aufgeworfen, dass die noch mitgeführten Körner durch die Strohmatte hindurchfallen. Unter jeder Horde ist eine Wanne auf der die Körner schräg nach vorne auf den Vorbereitungsboden laufen.
Der Schüttler ist jenes Abscheidesystem, welches das Stroh am wenigsten beansprucht und zerstört. Bei feuchtem oder unreifem Stroh sinkt die Abscheideleistung schnell. Bei der Fahrt bergauf steigen die Verluste ebenfalls, weil die Hangneigung der Schüttlerneigung entgegensteht. Am Seitenhang ist begrenzt die Horde an der Hangunterseite die Abscheideleistung. Unter diesen Bedingungen muss die Fahrgeschwindigkeit reduziert werden.
Axiale Abscheideelemente: Mähdrescher mit sehr breiten Schneidwerken werden darum mit axialen Abscheideelementen gebaut. Ein oder zwei (dann nebeneinander angeordnete) axiale Rotoren übernehmen die Aufgabe der Abscheidung. Durch die Fliehkräfte werden Korn und Stroh voneinander getrennt. Elemente aus einer Korbstruktur, die den Rotor mindestens unterhalb umschließen, verhindern, dass zu viele Nichtkornbestandteile auf die Reinigung gelangen und somit deren Funktionsfähigkeit einschränken. Bei axialen Systemen passiert das Stroh die Abscheidung rund zehnmal schneller als bei Schüttlersystemen. Daher sind größere Durchsätze möglich und vor allem bei feuchten Erntebedingungen ist der Kornverlust erheblich geringer. Axialmähdrescher sind zudem weniger anfällig gegen starke Hangneigungen, da hier die Schwerkraft weniger Bedeutung für die Abscheidung hat.

Getreide wird in aller Regel auf ebenen Flächen angebaut. Es gibt jedoch Regionen, wo auch in sanft hügeligen bis zum Teil recht steilen Topografien Druschfrüchte angebaut werden. Wie oben beschrieben, wird der Drusch- und Trennprozess in Mähdreschern sehr stark von der Topografie oder eben der Schwerkraft beeinflusst. Bereits die durch die Hangneigung einseitige Beschickung des Dreschwerkes reduziert die Leistungsfähigkeit der Maschine enorm, da nicht die ganze Dreschwerksbreite genutzt wird. Schlimmer jedoch ist die einseitige Beschickung der Reinigungsanlage (Vorbereitungsboden, Siebe) mit dem ausgedroschenen Gut. Spreu und Korn erreichen die Reinigungsanlage auf der hangabwärts liegenden Seite, darüber hinaus wird durch die Siebbewegung das Material weiter einseitig konzentriert.

Die Leistungseinbuße steigt exponentiell mit der Hangneigung. Es ist also von großem Interesse, die Hangneigung resp. diese Leistungseinbuße zu kompensieren. Dazu existieren verschiedene Systeme.
Ältestes Verfahren, das heute vor allem bei extremen Hanglagen noch immer angewandt wird, ist, dass das Fahrwerk so angehoben oder abgesenkt wird, dass die Dreschorgange waagerecht liegen. Der erste Mähdrescher mit einem Hangausgleich nach diesem Prinzip wurde 1891 von den Gebrüdern Holt in Kalifornien gebaut.[8] Der Hangausgleich musste bei früheren Maschinen mechanisch eingestellt werden, wofür eine zweite Person auf dem Mähdrescher notwendig war. Der erste automatische Hangausgleich wurde 1941 von Raymond A. Hanson entwickelt. 1945 stattete er die ersten Maschinen mit diesem System aus, bei dem der Grad der Neigung über Quecksilberschalter ermittelt wurde, und die Abscheideorgane über pneumatische Zylinder entsprechend ausgerichtet wurden.[9]

Heute geschieht der Ausgleich in der Regel mittels zweier Hydraulikzylinder, die den Mähdrescher einseitig von der Vorderachse abheben und somit waagerecht halten. Da die Hinterachse pendelnd gelagert ist, ist hier kein Neigungsausgleich erforderlich. Seltener ermöglicht eine Hubhydraulik an der Hinterachse auch einen Neigungsausgleich in Längsrichtung.

Problematisch ist hier der technische Aufwand und die damit verbundenen Kosten. Auch die Gutübergabe vom schrägen Schneidwerk auf den geraden Mähdrescher ist problematisch. Dieses System bietet jedoch den Vorteil, dass das komplette Fahrzeug mit Ausnahme des Schneidwerks in der Waagerechten gehalten wird. Somit wird die Leistung der Reinigungsorgane nicht durch die Seitenlage beeinträchtigt. Auch kann so das Volumen des Korntanks voll ausgenutzt werden, was nicht möglich ist, wenn das Fahrzeug zur Seite geneigt ist, da das Erntegut zu dieser Seite verrutschen würde, was in extremen Fällen sogar ein Umkippen des Fahrzeugs zur Folge haben kann. Darüber hinaus erhöht sich der Fahrkomfort, da auch der Fahrer in einer geraden Sitzposition verbleibt, und nicht aus dem Sitz zu rutschen droht.

Die in den letzten Jahren in vielen Bereichen stattfindende Unternehmenskonzentration ist auch auf dem Agrar-Sektor zu beobachten. Bei Mähdreschern tragen zusätzlich die hohen technologischen Anforderungen sowie die kapitalintensive Produktion dazu bei, dass viele früher eigenständige Unternehmen heute in einem Dachkonzern vereinigt sind. Dabei werden etablierte Markennamen teilweise nebeneinander beibehalten oder – etwa regional oder im Produktspektrum – differenziert. Während weniger bekannte oder angesehene Marken aufgegeben werden, können Unternehmen mit hochwertigem Image bisher nicht vorhandene Produktlinien unter eigenem Namen von Konzernschwestern übernehmen.

John Deere ist Weltmarktführer bei Landmaschinen.
Claas ist europäischer Marktführer für Mähdrescher.
Im CNH Global-Konzern, weltweit an zweiter Stelle der Landmaschinenproduzenten, ging unter anderem die DDR-Marke Fortschritt auf, heutige Marken sind
Case IH und
New Holland.
Die 1990 entstandene AGCO (Allis-Gleaner Corporation) vereinigte einige bekannte Marken:
Gleaner war von Beginn an der Markenname für Erntemaschinen.
Massey Ferguson wurde 1994 übernommen.
Fendt kam 1997 zum Konzern und bietet seit 1999 Mähdrescher unter eigenem Namen an.
Laverda ist seit 2010 im hundertprozentigen Konzernbesitz.
Deutz-Fahr ist das Nachfolgeunternehmen des ersten deutschen Produzenten.
Rostselmasch ist ein russischer Hersteller von u.a. Mähdreschern.
Sampo Rosenlew ist ein finnischer Hersteller von u.a. Mähdreschern.
Parzellendrescher für das Versuchswesen stellen die Firmen Zürn Harvesting [10] und Wintersteiger her.

The combine harvester, or simply combine, is a machine that harvests grain crops. The name derives from its combining three separate operations comprising harvesting—reaping, threshing, and winnowing—into a single process. Among the crops harvested with a combine are wheat, oats, rye, barley, corn (maize), soybeans and flax (linseed). The waste straw left behind on the field is the remaining dried stems and leaves of the crop with limited nutrients which is either chopped and spread on the field or baled for feed and bedding for livestock.

Combine harvesters are one of the most economically important labor saving inventions, enabling a small fraction of the population to be engaged in agriculture.

Scottish inventor Patrick Bell invented the reaper in 1826. The combine was invented in the United States by Hiram Moore in 1834, and early versions were pulled by horse or mule teams.[2] In 1835, Moore built a full-scale version and by 1839, over 50 acres of crops were harvested.[3] By 1860, combine harvesters with a cutting width of several metres were used on American farms.[4] In 1882, the Australian Hugh Victor McKay had a similar idea and developed the first commercial combine harvester in 1885, the Sunshine Harvester.[5]

Combines, some of them quite large, were drawn by mule or horse teams and used a bullwheel to provide power. Later, steam power was used, and George Stockton Berry integrated the combine with a steam engine using straw to heat the boiler.[6]Tractor-drawn, combines became common after World War II as many farms began to use tractors. These combines used a shaker to separate the grain from the chaff and straw-walkers (grates with small teeth on an eccentric shaft) to eject the straw while retaining the grain. Early tractor-drawn combines were usually powered by a separate gasoline engine, while later models were PTO-powered. These machines either put the harvested crop into bags that were then loaded onto a wagon or truck, or had a small bin that stored the grain until it was transferred to a truck or wagon with an auger.

In the U.S., Allis-Chalmers, Massey-Harris, International Harvester, Gleaner Manufacturing Company, John Deere, and Minneapolis Moline are past or present major combine producers.

In 1911, the Holt Manufacturing Company of California produced a self-propelled harvester.[7] In Australia in 1923, the patented Sunshine Auto Header was one of the first center-feeding self-propelled harvesters.[8] In 1923 in Kansas, the Curtis brothers and their Gleaner Manufacturing Company patented a self-propelled harvester which included several other modern improvements in grain handling.[9] Both the Gleaner and the Sunshine used Fordson engines. In 1929 Alfredo Rotania of Argentina patented a self-propelled harvester.[10] In 1937, the Australian-born Thomas Carroll, working for Massey-Harris in Canada, perfected a self-propelled model and in 1940 a lighter-weight model began to be marketed widely by the company.[11] Lyle Yost invented an auger that would lift grain out of a combine in 1947, making unloading grain much easier.[12]

In 1952 Claeys launched the first self- propelled combine harvester in Europe;[13] in 1953, the European manufacturer CLAAS developed a self-propelled combine harvester named ‘Herkules’, it could harvest up to 5 tons of wheat a day.[14] This newer kind of combine is still in use and is powered by diesel or gasoline engines. Until the self-cleaning rotary screen was invented in the mid-1960s combine engines suffered from overheating as the chaff spewed out when harvesting small grains would clog radiators, blocking the airflow needed for cooling.

A significant advance in the design of combines was the rotary design. The grain is initially stripped from the stalk by passing along a helical rotor instead of passing between rasp bars on the outside of a cylinder and a concave. Rotary combines were first introduced by Sperry-New Holland in 1975.[15]

In about the 1980s on-board electronics were introduced to measure threshing efficiency. This new instrumentation allowed operators to get better grain yields by optimizing ground speed and other operating parameters.

Combines are equipped with removable heads that are designed for particular crops. The standard header, sometimes called a grain platform, is equipped with a reciprocating knife cutter bar, and features a revolving reel with metal or plastic teeth to cause the cut crop to fall into the auger once it is cut. A variation of the platform, a "flex" platform, is similar but has a cutter bar that can flex over contours and ridges to cut soybeans that have pods close to the ground. A flex head can cut soybeans as well as cereal crops, while a rigid platform is generally used only in cereal grains.

Some wheat headers, called "draper" headers, use a fabric or rubber apron instead of a cross auger. Draper headers allow faster feeding than cross augers, leading to higher throughputs due to lower power requirements. On many farms, platform headers are used to cut wheat, instead of separate wheat headers, so as to reduce overall costs.

Dummy heads or pick-up headers feature spring-tined pickups, usually attached to a heavy rubber belt. They are used for crops that have already been cut and placed in windrows or swaths. This is particularly useful in northern climates such as western Canada where swathing kills weeds resulting in a faster dry down.

While a grain platform can be used for corn, a specialized corn head is ordinarily used instead. The corn head is equipped with snap rolls that strip the stalk and leaf away from the ear, so that only the ear (and husk) enter the throat. This improves efficiency dramatically since so much less material must go through the cylinder. The corn head can be recognized by the presence of points between each row.

Occasionally rowcrop heads are seen that function like a grain platform, but have points between rows like a corn head. These are used to reduce the amount of weed seed picked up when harvesting small grains.

Self-propelled Gleaner combines could be fitted with special tracks instead of tires or tires with tread measuring almost 10in deep to assist in harvesting rice. Some combines, particularly pull type, have tires with a diamond tread which prevents sinking in mud. These tracks can fit other combines by having adapter plates made.

The cut crop is carried up the feeder throat (commonly called the "feederhouse") by a chain and flight elevator, then fed into the threshing mechanism of the combine, consisting of a rotating threshing drum (commonly called the "cylinder"), to which grooved steel bars (rasp bars) are bolted. The rasp bars thresh or separate the grains and chaff from the straw through the action of the cylinder against the concave, a shaped "half drum", also fitted with steel bars and a meshed grill, through which grain, chaff and smaller debris may fall, whereas the straw, being too long, is carried through onto the straw walkers. This action is also allowed due to the fact that the grain is heavier than the straw, which causes it to fall rather than "float" across from the cylinder/concave to the walkers. The drum speed is variably adjustable on most machines, whilst the distance between the drum and concave is finely adjustable fore, aft and together, to achieve optimum separation and output. Manually engaged disawning plates are usually fitted to the concave. These provide extra friction to remove the awns from barley crops. After the primary separation at the cylinder, the clean grain falls through the concave and to the shoe, which contains the chaffer and sieves. The shoe is common to both conventional combines and rotary combines.

In the Palouse region of the Pacific Northwest of the United States the combine is retrofitted with a hydraulic hillside leveling system. This allows the combine to harvest the steep but fertile soil in the region. Hillsides can be as steep as a 50% slope. Gleaner, IH and Case IH, John Deere, and others all have made combines with this hillside leveling system, and local machine shops have fabricated them as an aftermarket add-on.

The first leveling technology was developed by Holt Co., a California firm, in 1891.[16] Modern leveling came into being with the invention and patent of a level sensitive mercury switch system invented by Raymond Alvah Hanson in 1946.[17] Raymond’s son, Raymond, Jr., produced leveling systems exclusively for John Deere combines until 1995 as R. A. Hanson Company, Inc. In 1995, his son, Richard, purchased the company from his father and renamed it RAHCO International, Inc. In March 2011, the company was renamed Hanson Worldwide, LLC.[18] Production continues to this day.

Hillside leveling has several advantages. Primary among them is an increased threshing efficiency on hillsides. Without leveling, grain and chaff slide to one side of separator and come through the machine in a large ball rather than being separated, dumping large amounts of grain on the ground. By keeping the machinery level, the straw-walker is able to operate more efficiently, making for more efficient threshing. IH produced the 453 combine which leveled both side-to-side and front-to-back, enabling efficient threshing whether on a hillside or climbing a hill head on.

Secondarily, leveling changes a combine’s center of gravity relative to the hill and allows the combine to harvest along the contour of a hill without tipping, a very real danger on the steeper slopes of the region; it is not uncommon for combines to roll on extremely steep hills.

Newer leveling systems do not have as much tilt as the older ones. A John Deere 9600 combine equipped with a Rahco hillside conversion kit will level over to 44%, while the newer STS combines will only go to 35%. These modern combines use the rotary grain separator which makes leveling less critical. Most combines on the Palouse have dual drive wheels on each side to stabilize them.

A leveling system was developed in Europe by the Italian combine manufacturer Laverda which still produces it today.

Sidehill combines are very similar to hillside combines in that they level the combine to the ground so that the threshing can be efficiently conducted; however, they have some very distinct differences. Modern hillside combines level around 35% on average, older machines were closer to 50%. Sidehill combines only level to 18%. They are sparsely used in the Palouse region. Rather, they are used on the gentle rolling slopes of the mid-west. Sidehill combines are much more mass-produced than their hillside counterparts. The height of a sidehill machine is the same height as a level-land combine. Hillside combines have added steel that sets them up approximately 2–5 feet higher than a level-land combine and provide a smooth ride.
Another technology that is sometimes used on combines is a continuously variable transmission. This allows the ground speed of the machine to be varied while maintaining a constant engine and threshing speed. It is desirable to keep the threshing speed constant since the machine will typically have been adjusted to operate best at a certain speed.

Self-propelled combines started with standard manual transmissions that provided one speed based on input rpm. Deficiencies were noted and in the early 1950s combines were equipped with what John Deere called the "Variable Speed Drive". This was simply a variable width sheave controlled by spring and hydraulic pressures. This sheave was attached to the input shaft of the transmission. A standard 4 speed manual transmission was still used in this drive system. The operator would select a gear, typically 3rd. An extra control was provided to the operator to allow him to speed up and slow down the machine within the limits provided by the variable speed drive system. By decreasing the width of the sheave on the input shaft of the transmission, the belt would ride higher in the groove. This slowed the rotating speed on the input shaft of the transmission, thus slowing the ground speed for that gear. A clutch was still provided to allow the operator to stop the machine and change transmission gears.

Later, as hydraulic technology improved, hydrostatic transmissions were introduced by Versatile Mfg for use on swathers but later this technology was applied to combines as well. This drive retained the 4 speed manual transmission as before, but this time used a system of hydraulic pumps and motors to drive the input shaft of the transmission. This system is called a Hydrostatic drive system. The engine turns the hydraulic pump capable of pressures up to 4,000 psi (30 MPa). This pressure is then directed to the hydraulic motor that is connected to the input shaft of the transmission. The operator is provided with a lever in the cab that allows for the control of the hydraulic motor’s ability to use the energy provided by the pump. By adjusting the swash plate in the motor, the stroke of its pistons are changed. If the swash plate is set to neutral, the pistons do not move in their bores and no rotation is allowed, thus the machine does not move. By moving the lever, the swash plate moves its attached pistons forward, thus allowing them to move within the bore and causing the motor to turn. This provides an infinitely variable speed control from 0 ground speed to what ever the maximum speed is allowed by the gear selection of the transmission. The standard clutch was removed from this drive system as it was no longer needed.

Most if not all modern combines are equipped with hydrostatic drives. These are larger versions of the same system used in consumer and commercial lawn mowers that most are familiar with today. In fact, it was the downsizing of the combine drive system that placed these drive systems into mowers and other machines.

Despite great advances mechanically and in computer control, the basic operation of the combine harvester has remained unchanged almost since it was invented.

First, the header, described above, cuts the crop and feeds it into the threshing cylinder. This consists of a series of horizontal rasp bars fixed across the path of the crop and in the shape of a quarter cylinder. Moving rasp bars or rub bars pull the crop through concaved grates that separate the grain and chaff from the straw. The grain heads fall through the fixed concaves. What happens next is dependent on the type of combine in question. In most modern combines, the grain is transported to the shoe by a set of 2, 3, or 4 (possibly more on the largest machines) augers, set parallel or semi-parallel to the rotor on axial mounted rotors and perpendicular Flow" combines.) In older Gleaner machines, these augers were not present. These combines are unique in that the cylinder and concave is set inside feederhouse instead of in the machine directly behind the feederhouse. Consequently, the material was moved by a "raddle chain" from underneath the concave to the walkers. The clean grain fell between the raddle and the walkers onto the shoe, while the straw, being longer and lighter, floated across onto the walkers to be expelled. On most other older machines, the cylinder was placed higher and farther back in the machine, and the grain moved to the shoe by falling down a "clean grain pan", and the straw "floated" across the concaves to the back of the walkers.

Since the Sperry-New Holland TR70 Twin-Rotor Combine came out in 1975, most manufacturers have combines with rotors in place of conventional cylinders. However, makers have now returned to the market with conventional models alongside their rotary line-up. A rotor is a long, longitudinally mounted rotating cylinder with plates similar to rub bars (except for in the above mentioned Gleaner rotaries).

There are usually two sieves, one above the other. The sieves and basically a metal frame, that has many rows of "fingers" set reasonably close together. The angle of the fingers is adjustable as to change the clearance and control the size of material passing through. The top is set with more clearance than the bottom as to allow a gradual cleaning action. Setting the concave clearance, fan speed, and sieve size is critical to ensure that the crop is threshed properly, the grain is clean of debris, and that all of the grain entering the machine reaches the grain tank or ‘hopper’. ( Observe, for example, that when travelling uphill the fan speed must be reduced to account for the shallower gradient of the sieves.)

Heavy material, e.g., unthreshed heads, fall off the front of the sieves and are returned to the concave for re-threshing.

The straw walkers are located above the sieves, and also have holes in them. Any grain remaining attached to the straw is shaken off and falls onto the top sieve.

When the straw reaches the end of the walkers it falls out the rear of the combine. It can then be baled for cattle bedding or spread by two rotating straw spreaders with rubber arms. Most modern combines are equipped with a straw spreader.

For some time, combine harvesters used the conventional design, which used a rotating cylinder at the front-end which knocked the seeds out of the heads, and then used the rest of the machine to separate the straw from the chaff, and the chaff from the grain. The TR70 from Sperry-New Holland was brought out in 1975 as the first rotary combine. Other manufacturers soon followed, IH with their ‘Axial Flow’ in 1977 and Gleaner with their N6 in 1979.

In the decades before the widespread adoption of the rotary combine in the late seventies, several inventors had pioneered designs which relied more on centrifugal force for grain separation and less on gravity alone. By the early eighties, most major manufacturers had settled on a "walkerless" design with much larger threshing cylinders to do most of the work. Advantages were faster grain harvesting and gentler treatment of fragile seeds, which were often cracked by the faster rotational speeds of conventional combine threshing cylinders.

It was the disadvantages of the rotary combine (increased power requirements and over-pulverization of the straw by-product) which prompted a resurgence of conventional combines in the late nineties. Perhaps overlooked but nonetheless true, when the large engines that powered the rotary machines were employed in conventional machines, the two types of machines delivered similar production capacities. Also, research was beginning to show that incorporating above-ground crop residue (straw) into the soil is less useful for rebuilding soil fertility than previously believed. This meant that working pulverized straw into the soil became more of a hindrance than a benefit. An increase in feedlot beef production also created a higher demand for straw as fodder. Conventional combines, which use straw walkers, preserve the quality of straw and allow it to be baled and removed from the field.

Grain combine fires are responsible for millions of dollars of loss each year. Fires usually start near the engine where dust and dry crop debris accumulate.[19] From 1984 to 2000, 695 major grain combine fires were reported to local fire departments.[20] Dragging chains to reduce static electricity was one method employed for preventing harvester fires, but the role of static electricity linked to causing harvester fires is yet to be established.
Quelle:
en.wikipedia.org/wiki/Combine_harvester
de.wikipedia.org/wiki/M%C3%A4hdrescher

Posted by !!! Painting with Light !!! #schauer on 2014-08-07 06:49:19

Tagged: , Schauer , Christian , Oberdiendorf , Thyrnau , Passau , Hauzenberg , Bayern , Bavaria , Deutschland , Germany , Ernte , Harvest , Harvester , Bauer , Farmer , Landwirt , Natur , Nature , Old , Alt , Nostalgie , Denim , Retro , Vintage , Farm , Bauernhof , Strom , Reifen , Wheel , Stahl , Steel , Outdoor , München , Munich , Deutz , Fahr , John , Deere , Landwirtschaft , Öko , Ökologie , Messer , Knife , Stroh , agricultor , agriculteur , Fahrzeug , Vehicle , Vehículo , véhicule , Mähdrescher , Traktor , Bulldog , tracteur , Tractor , agriculture , agricultura , récolte , cosecha , Kuh , Cow , Landschaft , Landscape , Feld , Field , Korn , Corn , Mais , driver , fahrer , Pussy , Paining , with , Light , Gras

One Night in October

One Night in October

Quelle:
de.wikipedia.org/wiki/Milchstra%C3%9Fe

en.wikipedia.org/wiki/Milky_Way

Die Milchstraße, auch Galaxis, ist die Galaxie, in der sich unser Sonnensystem mit der Erde befindet. Entsprechend ihrer Form als flache Scheibe, die aus Milliarden von Sternen besteht, ist die Milchstraße von der Erde aus als bandförmige Aufhellung am Nachthimmel sichtbar, die sich über 360° erstreckt. Ihrer Struktur nach zählt die Milchstraße zu den Balkenspiralgalaxien.
Den Namen Milchstraßensystem trägt unser Sternsystem nach der Milchstraße, die als freiäugige Innenansicht des Systems von der Erde aus wie ein quer über das Firmament gesetzter milchiger Pinselstrich erscheint. Dass dieses weißliche Band sich in Wirklichkeit aus unzähligen einzelnen Sternen zusammensetzt, wurde erst 1609 von Galileo Galilei erkannt, der die Erscheinung als Erster durch ein Fernrohr betrachtete. Es sind nach heutiger Schätzung ca. 100 bis 300 Milliarden Sterne.

Schon im Altertum war die Milchstraße als heller, schmaler Streifen am Nachthimmel bekannt. Ihr altgriechischer Name galaxias (γαλαξίας) – von dem auch der heutige Fachausdruck „Galaxis“ stammt – ist von dem Wort gala (γάλα, Milch) abgeleitet.[1] Wie dem deutschen Wort „Milchstraße“ liegt also auch dem altgriechischen Begriff das „milchige“ Aussehen zugrunde.

Eine antike griechische Sage versucht, diesen Begriff mythologisch zu erklären: Danach habe Zeus seinen Sohn Herakles, den ihm die sterbliche Frau Alkmene geschenkt hatte, an der Brust seiner göttlichen Frau Hera trinken lassen, als diese schlief. Herakles sollte auf diese Weise göttliche Kräfte erhalten. Aber er saugte so ungestüm, dass Hera erwachte und den ihr fremden Säugling zurückstieß; dabei wurde ein Strahl ihrer Milch über den ganzen Himmel verspritzt.

Einer germanischen Sage zufolge erhielt die Milchstraße nach dem Gott des Lichtes, Heimdall, auch Iring genannt, den Namen Iringsstraße (laut Felix Dahn, Walhall – germanische Götter- und Heldensagen). Die afrikanischen San gaben der Milchstraße den Namen „Rückgrat der Nacht“.

Zur ersten Vorstellung der Scheibenform des Milchstraßensystems gelangte bereits Wilhelm Herschel im Jahr 1785 aufgrund systematischer Sternzählungen (Stellarstatistik). Diese Methode konnte aber nicht zu einem realistischen Bild führen, da das Licht weiter entfernter Sterne stark durch interstellare Staubwolken abgeschwächt wird, ein Effekt, dessen wahre Bedeutung erst in der ersten Hälfte des 20. Jahrhunderts vollständig erfasst wurde. Durch Untersuchungen zur Verteilung der Kugelsternhaufen im Raum gelangte Harlow Shapley 1919 zu realistischen Abschätzungen der Größe des Milchstraßensystems und zu der Erkenntnis, dass die Sonne nicht – wie bis dahin, z. B. von Jacobus Kapteyn, angenommen – im Zentrum der Galaxis sitzt, sondern eher an deren Rand. Edwin Hubbles Messungen der Entfernungen von Spiralnebeln zeigten, dass diese außerhalb des Milchstraßensystems liegen und tatsächlich wie dieses eigenständige Galaxien sind.
Das Band der Milchstraße erstreckt sich als unregelmäßig breiter, schwach milchig-heller Streifen über dem Firmament.[2] Seine Erscheinung rührt daher, dass in ihm mit bloßem Auge keine Einzelsterne wahrgenommen werden, sondern eine Vielzahl lichtschwacher Sterne der galaktischen Scheibe und des Bulges (in Richtung des galaktischen Zentrums). Von der Südhalbkugel aus steht das helle Zentrum der Milchstraße hoch am Himmel, während man von der Nordhalbkugel zum Rand hin blickt. Daher kann man das Band der Milchstraße am besten von der Südhalbkugel aus beobachten. Im Dezember und Januar kann der hellste Bereich der Milchstraße nicht oder nur sehr schlecht beobachtet werden, weil sich die Sonne zwischen dem Zentrum der Galaxis und der Erde befindet. Gute Beobachtungsbedingungen sind bei klarer Luft und bei nur geringer Lichtverschmutzung durch künstliche Lichtquellen gegeben. Alle der maximal 6000 mit bloßem Auge sichtbaren Sterne des Nachthimmels gehören zum Milchstraßensystem.

Das Milchstraßenband verläuft unter anderem durch die Sternbilder Schütze (in dieser Richtung liegt auch das galaktische Zentrum), Adler, Schwan, Kassiopeia, Perseus, Fuhrmann, Zwillinge, Orion, Kiel des Schiffs, Zentaur, Kreuz des Südens und Skorpion. Die mittlere Ebene des Milchstraßensystems ist gegenüber dem Himmelsäquator um einen Winkel von etwa 63° gekippt.

Astronomen verwenden gelegentlich ein spezielles, an die Geometrie des Milchstraßensystems angepasstes galaktisches Koordinatensystem, bestehend aus Länge l und Breite b. Die galaktische Breite beträgt 0° in der Ebene des Milchstraßensystems, +90° am galaktischen Nordpol und −90° am galaktischen Südpol. Die galaktische Länge, die ebenfalls in Grad angegeben wird, hat ihren Ursprung (l = 0°) in Richtung des galaktischen Zentrums und nimmt nach Osten hin zu.

Die Erforschung der Struktur des Milchstraßensystems ist schwieriger als die der Strukturen anderer Galaxien, da Beobachtungen nur von einem Punkt innerhalb der Scheibe gemacht werden können. Wegen der erwähnten Absorption sichtbaren Lichts durch interstellaren Staub ist es nicht möglich, durch visuelle Beobachtungen ein vollständiges Bild des Milchstraßensystems zu erhalten. Große Fortschritte wurden erst gemacht, als Beobachtungen in anderen Wellenlängenbereichen, insbesondere im Radiofrequenzbereich und im Infraroten möglich wurden. Dennoch sind viele Details des Aufbaus der Galaxis noch nicht bekannt.

Das Milchstraßensystem wurde früher als vier- oder fünfarmig betrachtet, nun gilt es als zweiarmige Balkenspiralgalaxie.[3] Es besteht aus etwa 100 bis 300 Milliarden Sternen und großen Mengen interstellarer Materie, die nochmals 600 Millionen bis einige Milliarden Sonnenmassen ausmacht (die Anzahl der Sterne und damit auch die Gesamtmasse unserer Galaxis kann auf Basis von Berechnungen und Beobachtungen nur geschätzt werden, woraus sich der große Toleranzbereich der Zahlen ergibt). Die Masse dieses inneren Bereichs der Galaxis wird mit ungefähr 180 Milliarden Sonnenmassen veranschlagt. Ihre Ausdehnung in der galaktischen Ebene beträgt etwa 100.000 Lichtjahre (30 kpc), die Dicke der Scheibe etwa 3000 Lichtjahre (920 pc) und die der zentralen Ausbauchung (engl. Bulge) etwa 16.000 Lichtjahre (5 kpc). Zum Vergleich: Der Andromedanebel hat eine Ausdehnung von etwa 150.000 Lj. und das drittgrößte Mitglied der lokalen Gruppe, der Dreiecksnebel M 33, ca. 50.000 Lj. Die Angaben der Dicke müssen aber eventuell noch bis zum Doppelten nach oben korrigiert werden, wie der australische Wissenschaftler Bryan Gaensler und sein Team im Januar 2008 äußerten.[4][5] Aus der Bewegung interstellaren Gases und der Sternverteilung im Bulge ergibt sich für diesen eine längliche Form. Dieser Balken bildet mit der Verbindungslinie des Sonnensystems zum Zentrum des Milchstraßensystems einen Winkel von 45°. Die Galaxis ist also vermutlich eine Balkenspiralgalaxie vom Hubble-Typ SBc. Gemäß einer Bestimmung mithilfe des Infrarot-Weltraumteleskops Spitzer ist die Balkenstruktur mit einer Ausdehnung von 27.000 Lichtjahren überraschend lang.

Basierend auf der bekannten Umlaufzeit der Sonne und ihrem Abstand vom galaktischen Zentrum kann nach dem dritten keplerschen Gesetz zumindest die Gesamtmasse berechnet werden, die sich innerhalb der Sonnenbahn befindet.[6] Die Gesamtmasse des Milchstraßensystems wird auf etwa 400 Milliarden Sonnenmassen geschätzt,[7][8] damit ist sie neben dem Andromedanebel (800 Milliarden Sonnenmassen) die massereichste Galaxie der Lokalen Gruppe.

Galaktischer Halo
Umgeben ist die Galaxis vom kugelförmigen galaktischen Halo mit einem Durchmesser von etwa 165.000 Lichtjahren (50 kpc), einer Art von galaktischer „Atmosphäre“. In ihm befinden sich neben den etwa 150 bekannten Kugelsternhaufen nur weitere alte Sterne, darunter RR Lyrae-Veränderliche, und Gas sehr geringer Dichte. Ausnahme sind die heißen Blue-Straggler-Sterne. Dazu kommen große Mengen Dunkle Materie mit etwa 1 Billion Sonnenmassen, darunter auch so genannte MACHOs. Anders als die galaktische Scheibe ist der Halo weitgehend staubfrei und enthält fast ausschließlich Sterne der älteren, metallarmen Population II, deren Orbit sehr stark gegen die galaktische Ebene geneigt ist. Das Alter des inneren Teils des Halo wurde in einer im Mai 2012 vorgestellten neuen Methode zur Altersbestimmung vom Space Telescope Science Institute in Baltimore mit 11,4 Milliarden Jahren (mit einer Unsicherheit von 0,7 Milliarden Jahren) angegeben. Dem Astronomen Jason Kalirai vom Space Telescope Science Institute gelang diese Altersbestimmung durch den Vergleich der Halo-Zwerge der Milchstraße mit den gut untersuchten Zwergen im Kugelsternhaufen Messier 4, die im Sternbild Skorpion liegen.[9]

Galaktische Scheibe
Der Großteil der Sterne innerhalb der Galaxis ist annähernd gleichmäßig auf die galaktische Scheibe verteilt. Sie enthält im Gegensatz zum Halo vor allem Sterne der Population I, welche sich durch einen hohen Anteil schwerer Elemente auszeichnen.

Spiralarme
Teil der Scheibe sind auch die für das Milchstraßensystem charakteristischen Spiralarme. In den Spiralarmen befinden sich enorme Ansammlungen von Wasserstoff und auch die größten HII-Regionen, die Sternentstehungsgebiete der Galaxis. Daher befinden sich dort auch viele Protosterne, junge Sterne des T-Tauri-Typs und Herbig-Haro-Objekte. Während ihrer Lebenszeit bewegen sich Sterne von ihren Geburtsstätten weg und verteilen sich auf die Scheibe. Besonders massereiche und leuchtkräftige Sterne entfernen sich allerdings aufgrund ihrer kürzeren Lebensdauer nicht so weit von den Spiralarmen, weswegen diese hervortreten. Daher gehören zu den dort befindlichen stellaren Objekten vor allem Sterne der Spektralklassen O und B, Überriesen und Cepheiden, alle jünger als 100 Millionen Jahre. Sie stellen jedoch nur etwa ein Prozent der Sterne im Milchstraßensystem. Der größte Teil der Masse der Galaxis besteht aus alten, massearmen Sternen. Der „Zwischenraum“ zwischen den Spiralarmen ist also nicht leer, sondern ist einfach nur weniger leuchtstark.
Die Spiralstruktur der Galaxis konnte durch die Beobachtung der Verteilung von neutralem Wasserstoff bestätigt werden. Die entdeckten Spiralarme wurden nach den in ihrer Richtung liegenden Sternbildern benannt.

Die Zeichnung rechts stellt den Aufbau des Milchstraßensystems schematisch dar. Das Zentrum ist im sichtbaren Licht nicht direkt beobachtbar, ebenso wie der hinter ihm liegende Bereich. Die Sonne (gelber Kreis) liegt zwischen den Spiralarmen Sagittarius (nach Sternbild Schütze) und Perseus im Orionarm. Vermutlich ist dieser Arm nicht vollständig, siehe braune Linie in der Abbildung. Im Verhältnis zu dieser unmittelbaren Umgebung bewegt sich die Sonne mit etwa 30 km/s in Richtung des Sternbildes Herkules. Der innerste Arm ist der Norma-Arm (nach Sternbild Winkelmaß, auch 3-kpc-Arm), der äußerste (nicht in der Abbildung) ist der Cygnus-Arm (nach Sternbild Schwan), welcher vermutlich die Fortsetzung des Scutum-Crux-Arms (nach Sternbildern Schild und Kreuz des Südens) ist .

Wissenschaftler der Universität von Wisconsin veröffentlichten im Juni 2008 Auswertungen von Infrarotaufnahmen des Spitzer-Teleskopes, die das Milchstraßensystem nun als zweiarmige Galaxie darstellen. Sagittarius und Norma sind in dieser Darstellung nur noch als dünne Nebenarme erkenntlich, da diese nur durch eine überschüssige Verteilung von Gas gekennzeichnet sind während die restlichen beiden Arme durch eine hohe Dichte alter rötlicher Sterne gekennzeichnet sind.[10] Eine jüngere Untersuchung der Verteilung von Sternentstehungsgebieten und junger Sterne scheint hingegen die bekannte vierarmige Struktur der Milchstraße zu bestätigen.[11] Die Milchstraße besteht daher scheinbar aus vier Spiralarmen die sich primär durch Gaswolken und junge Sterne abzeichnen, wobei zwei Arme zusätzlich durch eine hohe Konzentration älterer Sterne charakterisiert sind. Neben diesen unterschiedlichen Auffassungen bezüglich der Struktur der Galaxis sollte beachtet werden, dass ein klar definiertes logarithmisches Spiralmuster nur in seltenen Fällen bei anderen Spiralgalaxien über die Gesamtheit der Scheibe beobachtet werden kann und die vorhandenen Arme oft extreme Abzweigungen, Verästelungen und Verschränkungen aufweisen.[12][13] Die wahrscheinliche Natur des lokalen Arms als solche Unregelmäßigkeit ist ein Hinweis darauf, dass solche Strukturen in der Milchstraße häufig auftreten könnten.[14]

Welche Prozesse für die Entstehung der Spiralstruktur verantwortlich sind, ist bislang noch nicht eindeutig geklärt. Jedoch ist klar, dass die zu den Spiralarmen gehörigen Sterne keine starre Struktur sind, die sich in Formation um das galaktische Zentrum dreht. Wäre dies der Fall, würde sich die Spiralstruktur des Milchstraßensystems und anderer Spiralgalaxien aufgrund der unterschiedlichen Bahngeschwindigkeiten innerhalb relativ kurzer Zeit aufwickeln und unkenntlich werden. Eine Erklärung bietet die Dichtewellentheorie, nach der die Spiralarme Zonen erhöhter Materiedichte und Sternentstehung sind, die sich unabhängig von den Sternen durch die Scheibe bewegen. Die durch die Spiralarme verursachten Störungen in den Bahnen der Sterne können zu Lindblad-Resonanzen führen.

Sterne der galaktischen Scheibe
Die zur Population I zählenden Sterne der galaktischen Scheibe lassen sich mit zunehmender Streuung um die Hauptebene und Alter in drei Unterpopulationen einteilen. Die so genannte „Thin Disk“ in einem Bereich von 700 bis 800 Lichtjahren über und unterhalb der galaktischen Ebene enthält neben den oben genannten leuchtkräftigen Sternen der Spiralarme, die sich nur maximal 500 Lichtjahre von der Ebene entfernen, Sterne der Spektralklassen A und F, einige Riesen der Klassen A, F, G und K, sowie Zwergsterne der Klassen G, K und M und auch einige Weiße Zwerge. Die Metallizität dieser Sterne ist vergleichbar mit der der Sonne, meist aber auch doppelt so hoch, ihr Alter liegt bei etwa einer Milliarde Jahren.

Eine weitere Gruppe ist die der mittelalten Sterne (Alter bis zu fünf Milliarden Jahre). Dazu zählen die Sonne und weitere Zwergsterne der Spektraltypen G, K und M, sowie einige Unter- und Rote Riesen. Der Metallgehalt ist hier deutlich geringer mit nur etwa 50 bis 100 Prozent dessen der Sonne. Auch ist die Bahnexzentrizität der galaktischen Orbits dieser Sterne höher und sie befinden sich nicht weiter als 1500 Lichtjahre über oder unterhalb der galaktischen Ebene.

Zwischen maximal 2500 Lichtjahren ober- und unterhalb der Hauptebene erstreckt sich die „Thick Disk“. Dort befinden sich rote K- und M-Zwerge, Weiße Zwerge, sowie einige Unterriesen und Rote Riesen, aber auch langperiodische Veränderliche. Ihr Alter erreicht bis zu zehn Milliarden Jahre und sie sind vergleichsweise metallarm (etwa ein Viertel der Sonnenmetallizität). Diese Population ähnelt auch vielen Sternen im Bulge.

Die galaktische Scheibe ist nicht vollkommen gerade, durch gravitative Wechselwirkung mit den Magellanschen Wolken ist sie leicht in deren Richtung gebogen.

Das Zentrum des Milchstraßensystems liegt im Sternbild Schütze und ist hinter dunklen Staub- und Gaswolken verborgen, so dass es im sichtbaren Licht nicht direkt beobachtet werden kann. Beginnend in den 1950er Jahren ist es gelungen, im Radiowellenbereich sowie mit Infrarotstrahlung und Röntgenstrahlung zunehmend detailreichere Bilder aus der nahen Umgebung des galaktischen Zentrums zu gewinnen. Man hat dort eine starke Radioquelle entdeckt, bezeichnet als Sagittarius A* (Sgr A*), die aus einem sehr kleinen Gebiet strahlt. Diese Massenkonzentration wird von einer Gruppe von Sternen in einem Radius von weniger als einem halben Lichtjahr mit einer Umlaufzeit von etwa 100 Jahren sowie einem Schwarzen Loch mit 1300 Sonnenmassen in drei Lichtjahren Entfernung umkreist. Der dem zentralen Schwarzen Loch am nächsten liegende Stern S2 umläuft das galaktische Zentrum in einer Entfernung von etwa 17 Lichtstunden in einem Zeitraum von nur 15,2 Jahren. Seine Bahn konnte inzwischen über einen vollen Umlauf hinweg beobachtet werden. Aus den Beobachtungen der Bewegungen der Sterne des zentralen Sternhaufens ergibt sich, dass sich innerhalb dieser Region von 15,4 Millionen km Durchmesser eine Masse von geschätzten 4,31 Millionen Sonnenmassen befinden muss.[15] Die im Rahmen der Relativitätstheorie plausibelste und einzige mit allen Beobachtungen konsistente Erklärung für diese große Massenkonzentration ist die Anwesenheit eines Schwarzen Lochs.

Am 9. November 2010 machte Doug Finkbeiner vom Harvard-Smithsonian Center for Astrophysics bekannt, dass er zwei riesenhafte kugelförmige Blasen entdeckt habe, die aus der Mitte der Milchstraße nach Norden und Süden hinausgreifen. Die Entdeckung ist mit der Hilfe von Daten des Fermi Gamma-ray Space Telescope gelungen. Der Durchmesser der Blasen beträgt jeweils etwa 25.000 Lichtjahre; sie erstrecken sich am südlichen Nachthimmel von der Jungfrau bis zum Kranich. Ihr Ursprung ist bisher noch nicht geklärt.[16][17]

Größenvergleich
Man bekommt eine anschauliche Vorstellung von der Größe unserer Galaxis mit ihren 100 bis 300 Milliarden Sternen, wenn man sie sich im Maßstab 1:1017 verkleinert als Schneetreiben auf einem Gebiet von 10 km Durchmesser und einer Höhe von etwa 1 km im Mittel vorstellt. Jede Schneeflocke entspricht dabei einem Stern und es gibt etwa drei Stück pro Kubikmeter. Unsere Sonne hätte in diesem Maßstab einen Durchmesser von etwa 10 nm, wäre also kleiner als ein Virus. Selbst die Plutobahn, die sich im Mittel etwa 40-mal so weit von der Sonne befindet wie die Bahn der Erde, läge mit einem Durchmesser von 0,1 mm an der Grenze der visuellen Sichtbarkeit. Pluto selbst hätte ebenso wie die Erde lediglich atomare Dimension. Damit demonstriert dieses Modell auch die geringe durchschnittliche Massendichte unserer Galaxis.
Die Sonne umkreist das Zentrum des Milchstraßensystems in einem Abstand von 25.000 bis 28.000 Lichtjahren (≈ 250 Em oder 7,94 ± 0,42 kpc)[18] und befindet sich nördlich der Mittelebene der galaktischen Scheibe innerhalb des Orion-Arms, in einem weitgehend staubfreien Raumgebiet, das als „Lokale Blase“ bekannt ist. Für einen Umlauf um das Zentrum der Galaxis, ein so genanntes galaktisches Jahr, benötigt sie 220 bis 240 Millionen Jahre, was einer Rotationsgeschwindigkeit von etwa 220 km/s entspricht. Die Erforschung dieser Rotation ist mittels der Eigenbewegung und der Radialgeschwindigkeit vieler Sterne möglich; aus ihnen wurden um 1930 die Oortschen Rotationsformeln abgeleitet. Heutzutage kann auch die durch die Umlaufbewegung des Sonnensystems bedingte scheinbare Bewegung des Milchstraßenzentrums gegenüber Hintergrundquellen direkt beobachtet werden, so dass die Umlaufgeschwindigkeit des Sonnensystems unmittelbar messbar ist.[19] Neuere Messungen haben eine Umlaufgeschwindigkeit von ca. 267 km/s (961.200 km/h) ergeben.[20]

Das Sonnensystem umläuft das galaktische Zentrum nicht auf einer ungestörten ebenen Keplerbahn. Die in der Scheibe des Milchstraßensystems verteilte Masse übt eine starke Störung aus, so dass die Sonne zusätzlich zu ihrer Umlaufbahn um das Zentrum auch regelmäßig durch die Scheibe auf und ab oszilliert. Die Scheibe durchquert sie dabei etwa alle 30 bis 45 Millionen Jahre einmal.[21] Vor ca. 1,5 Millionen Jahren hat sie die Scheibe in nördlicher Richtung passiert und befindet sich jetzt etwa 65 Lichtjahre (ca. 20 pc)[22] über ihr. Die größte Entfernung wird etwa 250 Lichtjahre (80 pc) betragen, dann kehrt sich die Bewegung wieder um.[21]

Größere datierbare Krater auf der Erde sowie erdgeschichtliche Massenaussterben scheinen eine Periodizität von 34 bis 37 Millionen Jahren aufzuweisen, was auffällig mit der Periodizität der Scheibenpassagen übereinstimmt. Möglicherweise stören während einer Scheibendurchquerung die in Scheibennähe stärker werdenden Gravitationsfelder die Oortsche Wolke des Sonnensystems, so dass eine größere Anzahl von Kometen ins innere Sonnensystem gelangt und die Anzahl schwerer Impakte auf der Erde zunimmt. Die betreffenden Perioden sind jedoch bisher nicht genau genug bekannt, um definitiv einen Zusammenhang festzustellen;[21] neuere Ergebnisse (Scheibendurchgang alle 42 ± 2 Millionen Jahre) sprechen eher dagegen.[23] Eine neue Studie des Max-Planck Instituts für Astronomie hat gezeigt, dass es sich bei der scheinbaren Periodizität der Einschläge um statistische Artefakte handelt und es keinen solchen Zusammenhang gibt.

Um das Milchstraßensystem herum sind einige Zwerggalaxien versammelt. Die bekanntesten davon sind die Große und die Kleine Magellansche Wolke, mit denen das Milchstraßensystem über eine etwa 300.000 Lichtjahre lange Wasserstoffgasbrücke, dem Magellanschen Strom, verbunden ist.

Die dem Milchstraßensystem am nächsten gelegene Galaxie ist der Canis-Major-Zwerg, mit einer Entfernung von 42.000 Lichtjahren vom Zentrum des Milchstraßensystems und 25.000 Lichtjahren von unserem Sonnensystem. Die Zwerggalaxie wird zurzeit von den Gezeitenkräften des Milchstraßensystems auseinandergerissen und hinterlässt dabei ein Filament aus Sternen, das sich um die Galaxis windet, den so genannten Monoceros-Ring. Ob es sich dabei allerdings tatsächlich um die Überreste einer Zwerggalaxie oder um eine zufällige, projektionsbedingte Häufung handelt, ist derzeit noch nicht sicher. Andernfalls wäre die 50.000 Lichtjahre vom galaktischen Zentrum entfernte Sagittarius-Zwerggalaxie die nächste Galaxie, die ebenfalls gerade durch das Milchstraßensystem einverleibt wird.

Das Milchstraßensystem verleibt sich beständig Zwerggalaxien ein und nimmt dadurch an Masse zu. Während der Verschmelzung hinterlassen die Zwergsysteme Ströme aus Sternen und interstellarer Materie, die durch die Gezeitenkräfte des Milchstraßensystems aus den kleinen Galaxien herausgerissen werden (siehe auch: Wechselwirkende Galaxien). Dadurch entstehen Strukturen wie der Magellansche Strom, der Monoceros-Ring und der Virgo-Strom, sowie die anderen Hochgeschwindigkeitswolken in der Umgebung unserer Galaxis.

Lokale Gruppe
Mit der Andromeda-Galaxie, dem Dreiecksnebel (M 33) und einigen anderen kleineren Galaxien bildet das Milchstraßensystem die Lokale Gruppe, wobei das Milchstraßensystem die massereichste Galaxie darunter ist, obwohl es nicht die größte Ausdehnung besitzt. Die Lokale Gruppe ist Bestandteil des Virgo-Superhaufens, der nach dem Virgohaufen in seinem Zentrum benannt ist. Auf diesen bewegt sich die Lokale Gruppe zu. Der lokale Superhaufen strebt mit anderen Großstrukturen dem Shapley-Superhaufen entgegen (die frühere Annahme, Ziel dieses Strebens sei der Große Attraktor, ist überholt).[25]

Die Andromeda-Galaxie ist eine der wenigen Galaxien im Universum, deren Spektrum eine Blauverschiebung aufweist: Die Andromeda-Galaxie und das Milchstraßensystem bewegen sich mit einer Geschwindigkeit von 120 km/s aufeinander zu. Allerdings gibt die Blauverschiebung nur Aufschluss über die Geschwindigkeitskomponente parallel zur Verbindungslinie beider Systeme, während die Komponente senkrecht zu dieser Linie unbekannt ist. Vermutlich werden die beiden Galaxien in etwa drei Milliarden Jahren zusammenstoßen und zu einer größeren Galaxie verschmelzen. Für den Ablauf der Kollision können mangels Kenntnis der Raumgeschwindigkeiten und wegen der Komplexität der beim Zusammenstoß ablaufenden Prozesse nur Wahrscheinlichkeitsaussagen gemacht werden.[26] Nach der Verschmelzung der beiden Galaxien wird das Endprodukt voraussichtlich eine massereiche elliptische Galaxie sein. Als Name für diese Galaxie wird von Cox-Loeb 2008 in ihrem Artikel der Arbeitsname „Milkomeda“ benutzt, eine Verschmelzung des englischen Milky Way und Andromeda.[26]

Alter
Messungen aus dem Jahr 2004 zufolge ist das Milchstraßensystem etwa 13,6 Milliarden Jahre alt. Die Genauigkeit dieser Abschätzung, die das Alter anhand des Berylliumanteils einiger Kugelsternhaufen bestimmt, wird mit etwa 800 Millionen Jahren angegeben. Da das Alter des Universums von 13,8 Milliarden Jahren als recht verlässlich bestimmt gilt, hieße das, dass die Entstehung der Milchstraße auf die Frühzeit des Universums datiert.

2007 wurde zunächst für den Stern HE 1523-0901 im galaktischen Halo von der ESO-Sternwarte in Hamburg ein Alter von 13,2 Milliarden Jahren festgestellt[27]. 2014 wurde dann für den Stern SM0313, 6000 Lj von der Erde entfernt, von der Australian National University ein Alter von 13,6 Milliarden Jahren dokumentiert. Als älteste bekannte Objekte der Milchstraße setzen diese Datierungen eine unterste Grenze, die im Bereich der Messgenauigkeit der Abschätzung von 2004 liegt.

Nach derselben Methode kann das Alter der dünnen galaktischen Scheibe durch die ältesten dort gemessenen Objekte abgeschätzt werden, wodurch sich ein Alter von etwa 8,8 Milliarden Jahren mit einer Schätzbreite von etwa 1,7 Milliarden Jahren ergibt. Auf dieser Basis ergäbe sich eine zeitliche Lücke von etwa drei bis sieben Milliarden Jahren zwischen der Bildung des galaktischen Zentrums und der äußeren Scheibe.

The Milky Way is the galaxy that contains our Solar System.[15][16][17][nb 1] Its name “milky” is derived from its appearance as a dim glowing band arching across the night sky in which the naked eye cannot distinguish individual stars. The term “Milky Way” is a translation of the Latin via lactea, from the Greek γαλαξίας κύκλος (galaxías kýklos, "milky circle").[18][19][20] From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Up until the early 1920s, most astronomers thought that all of the stars in the universe were contained inside of the Milky Way. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis,[21] observations by Edwin Hubble definitively showed that the Milky Way is just one of many billions of galaxies.[22]

The Milky Way is a barred spiral galaxy some 100,000–120,000 light-years in diameter, which contains 100–400 billion stars. It may contain at least as many planets as well.[23][24] The Solar System is located within the disk, about 27,000 light-years away from the Galactic Center, on the inner edge of one of the spiral-shaped concentrations of gas and dust called the Orion Arm. The stars in the inner ≈10,000 light-years form a bulge and one or more bars that radiate from the bulge. The very center is marked by an intense radio source, named Sagittarius A*, which is likely to be a supermassive black hole.

Stars and gases at a wide range of distances from the Galactic Center orbit at approximately 220 kilometers per second. The constant rotation speed contradicts the laws of Keplerian dynamics and suggests that much of the mass of the Milky Way does not emit or absorb electromagnetic radiation. This mass has been given the name “dark matter”.[25] The rotational period is about 240 million years at the position of the Sun.[11] The Milky Way as a whole is moving at a velocity of approximately 600 km per second with respect to extragalactic frames of reference. The oldest known star in the Milky Way is at least 13.82 [26] billion years old and thus must have formed shortly after the Big Bang.[7]

Surrounded by several smaller satellite galaxies, the Milky Way is part of the Local Group of galaxies, which forms a subcomponent of the Virgo Supercluster, which again forms a subcomponent of the Laniakea supercluster.
When observing the night sky, the term “Milky Way” is limited to the hazy band of white light some 30 degrees wide arcing across the sky.[29] Although all of the individual stars that can be seen in the entire sky with the naked eye are part of the Milky Way Galaxy,[30] the light in this band originates from the accumulation of un-resolved stars and other material when viewed in the direction of the Galactic plane. Dark regions within the band, such as the Great Rift and the Coalsack, correspond to areas where light from distant stars is blocked by interstellar dust.

The Milky Way has a relatively low surface brightness. Its visibility can be greatly reduced by background light such as light pollution or stray light from the Moon. It is readily visible when the limiting magnitude is +5.1 or better and shows a great deal of detail at +6.1.[31] This makes the Milky Way difficult to see from any brightly lit urban or suburban location, but very prominent when viewed from a rural area when the Moon is below the horizon.[nb 2]

As viewed from Earth, the visible region of the Milky Way’s Galactic plane occupies an area of the sky that includes 30 constellations. The center of the Milky Way lies in the direction of the constellation Sagittarius; it is here that the Milky Way is brightest. From Sagittarius, the hazy band of white light appears to pass westward to the Galactic anticenter in Auriga. The band then continues westward the rest of the way around the sky, back to Sagittarius. The band divides the night sky into two roughly equal hemispheres.

The Galactic plane is inclined by about 60 degrees to the ecliptic (the plane of Earth’s orbit). Relative to the celestial equator, it passes as far north as the constellation of Cassiopeia and as far south as the constellation of Crux, indicating the high inclination of Earth’s equatorial plane and the plane of the ecliptic, relative to the Galactic plane. The north Galactic pole is situated at right ascension 12h 49m, declination +27.4° (B1950) near β Comae Berenices, and the south Galactic pole is near α Sculptoris. Because of this high inclination, depending on the time of night and year, the arc of Milky Way may appear relatively low or relatively high in the sky. For observers from approximately 65 degrees north to 65 degrees south on Earth’s surface, the Milky Way passes directly overhead twice a day.
The stellar disk of the Milky Way Galaxy is approximately 100,000 ly (30 kpc) in diameter, and is, on average, about 1,000 ly (0.3 kpc) thick.[2][3] As a guide to the relative physical scale of the Milky Way, if it were reduced to 100 m in diameter, the Solar System, including the hypothesized Oort cloud, would be no more than 1 mm in width, about the size of a grain of sand. The nearest star, Proxima Centauri, would be 4.2 mm distant.[nb 3] Alternatively visualized, if the Solar System out to Neptune were the size of a US quarter (25mm), the Milky Way would have a diameter of 4,000 kilometers, or approximately the breadth of the United States.

Estimates for the mass of the Milky Way vary, depending upon the method and data used. At the low end of the estimate range, the mass of the Milky Way is 5.8×1011 solar masses (M☉), somewhat smaller than the Andromeda Galaxy.[33][34][35] Measurements using the Very Long Baseline Array in 2009 found velocities as large as 254 km/s for stars at the outer edge of the Milky Way.[36] As the orbital velocity depends on the total mass inside the orbital radius, this suggests that the Milky Way is more massive, roughly equaling the mass of Andromeda Galaxy at 7×1011 M☉ within 160,000 ly (49 kpc) of its center.[37] A 2010 measurement of the radial velocity of halo stars finds the mass enclosed within 80 kiloparsecs is 7×1011 M☉.[38] According to a study published in 2014, the mass of the entire Milky Way is estimated to be 8.5×1011 M☉,[39] which is about half the mass of the Andromeda Galaxy.[39]

Most of the mass of the Milky Way appears to be matter of unknown form that interacts with other matter through gravitational but not electromagnetic forces, which is dubbed dark matter. A dark matter halo is spread out relatively uniformly to a distance beyond one hundred kiloparsecs from the Galactic Center. Mathematical models of the Milky Way suggest that the total mass of the entire Galaxy lies in the range 1–1.5×1012 M☉.[8] More recent studies indicate a mass as large as 4.5×1012 M☉ [40] and as small as 0.8×1012 M☉.[41] The Milky Way contains at least 100 billion planets[42] and between 200 and 400 billion stars.[43][44] The exact figure depends on the number of very low-mass, or dwarf stars, which are hard to detect, especially at distances of more than 300 ly (90 pc) from the Sun. As a comparison, the neighboring Andromeda Galaxy contains an estimated one trillion (1012) stars.[45] Filling the space between the stars is a disk of gas and dust called the interstellar medium. This disk has at least a comparable extent in radius to the stars,[46] whereas the thickness of the gas layer ranges from hundreds of light years for the colder gas to thousands of light years for warmer gas.[47][48] Both gravitational microlensing and planetary transit observations indicate that there may be at least as many planets bound to stars as there are stars in the Milky Way[23][49] and microlensing measurements indicate that there are more rogue planets not bound to host stars than there are stars.[50][51] The Milky Way Galaxy contains at least one planet per star, resulting in 100–400 billion planets, according to a January 2013 study of the five-planet star system Kepler-32 with the Kepler space observatory.[24] A different January 2013 analysis of Kepler data estimated that at least 17 billion Earth-sized exoplanets reside in the Milky Way Galaxy.[52] On November 4, 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of Sun-like stars and red dwarfs within the Milky Way Galaxy.[53][54][55] 11 billion of these estimated planets may be orbiting sun-like stars.[56] The nearest such planet may be 12 light-years away, according to the scientists.[53][54] Such Earth-sized planets may be more numerous than gas giants.[23] Besides exoplanets, "exocomets", comets beyond the Solar System, have also been detected and may be common in the Milky Way Galaxy.[52]

The disk of stars in the Milky Way does not have a sharp edge beyond which there are no stars. Rather, the concentration of stars decreases with distance from the center of the Milky Way. For reasons that are not understood, beyond a radius of roughly 40,000 ly (13 kpc) from the center, the number of stars per cubic parsec drops much faster with radius.[57] Surrounding the Galactic disk is a spherical Galactic Halo of stars and globular clusters that extends further outward, but is limited in size by the orbits of two Milky Way satellites, the Large and the Small Magellanic Clouds, whose closest approach to the Galactic Center is about 180,000 ly (55 kpc).[58] At this distance or beyond, the orbits of most halo objects would be disrupted by the Magellanic Clouds. Hence, such objects would probably be ejected from the vicinity of the Milky Way. The integrated absolute visual magnitude of the Milky Way is estimated to be −20.9.

The Milky Way consists of a bar-shaped core region surrounded by a disk of gas, dust and stars. The gas, dust and stars are organized in roughly logarithmic spiral arm structures (see Spiral arms below). The mass distribution within the Milky Way closely resembles the type SBc in the Hubble classification, which represents spiral galaxies with relatively loosely wound arms.[1] Astronomers first began to suspect that the Milky Way is a barred spiral galaxy, rather than an ordinary spiral galaxy, in the 1990s.[61] Their suspicions were confirmed by the Spitzer Space Telescope observations in 2005[62] that showed the Milky Way’s central bar to be larger than previously suspected.

Galactic quadrants
Main article: Galactic quadrant
A galactic quadrant, or quadrant of the galaxy, refers to one of four circular sectors in the division of the Milky Way. In actual astronomical practice, the delineation of the galactic quadrants is based upon the galactic coordinate system, which places the Sun as the pole of the mapping system.

Quadrants are described using ordinals—for example, "1st galactic quadrant",[63] "second galactic quadrant",[64] or "third quadrant of the Galaxy".[65] Viewing from the north galactic pole with 0 degrees (°) as the ray that runs starting from the Sun and through the Galactic Center, the quadrants are as follow:

1st galactic quadrant – 0° ≤ longitude (ℓ) ≤ 90°[66] 2nd galactic quadrant – 90° ≤ ℓ ≤ 180°[64] 3rd galactic quadrant – 180° ≤ ℓ ≤ 270°[65] 4th galactic quadrant – 270° ≤ ℓ ≤ 360° (0°)[63] The Sun is 26,000–28,000 ly (8.0–8.6 kpc) from the Galactic Center. This value is estimated using geometric-based methods or by measuring selected astronomical objects that serve as standard candles, with different techniques yielding various values within this approximate range.[10][67][68][69][70] In the inner few kpc (around 10,000 light-years radius) is a dense concentration of mostly old stars in a roughly spheroidal shape called the bulge.[71] It has been proposed that the Milky Way lacks a bulge formed due to a collision and merger between previous galaxies and that instead has a pseudobulge formed by its central bar.[72]

The Galactic Center is marked by an intense radio source named Sagittarius A*. The motion of material around the center indicates that Sagittarius A* harbors a massive, compact object.[73] This concentration of mass is best explained as a supermassive black hole[nb 4][10][67] with an estimated mass of 4.1–4.5 million times the mass of the Sun.[67] Observations indicate that there are supermassive black holes located near the center of most normal galaxies.[74][75]

The nature of the Milky Way’s bar is actively debated, with estimates for its half-length and orientation spanning from 1–5 kpc (3,000–16,000 ly) and 10–50 degrees relative to the line of sight from Earth to the Galactic Center.[69][70][76] Certain authors advocate that the Milky Way features two distinct bars, one nestled within the other.[77] In most galaxies, Wang et al. report, the rate of accretion of the supermassive black hole is slow, but the Milky Way seems to be an important exception. X-ray emission is aligned with the massive stars surrounding the central bar.[78] However, RR Lyr variables do not trace a prominent Galactic bar.[70][79][80] The bar may be surrounded by a ring called the "5-kpc ring" that contains a large fraction of the molecular hydrogen present in the Milky Way, as well as most of the Milky Way’s star-formation activity. Viewed from the Andromeda Galaxy, it would be the brightest feature of the Milky Way.[81]

In 2010, two gigantic spherical bubbles of high energy emission were detected to the north and the south of the Milky Way core, using data of the Fermi Gamma-ray Space Telescope. The diameter of each of the bubbles is about 25,000 light-years (7.7 kpc); they stretch up to Grus and to Virgo on the night-sky of the southern hemisphere.[82][83] Subsequently, observations with the Parkes Telescope at radio frequencies identified polarized emission that is associated with the Fermi bubbles. These observations are best interpreted as a magnetized outflow driven by star formation in the central 640 ly (200 pc) of the Milky Way.[84]

Spiral arms
Outside the gravitational influence of the Galactic bars, astronomers generally organize the structure of the interstellar medium and stars in the disk of the Milky Way into four spiral arms.[85] Spiral arms typically contain a higher density of interstellar gas and dust than the Galactic average as well as a greater concentration of star formation, as traced by H II regions[86][87] and molecular clouds.[88]

Maps of the Milky Way’s spiral structure are notoriously uncertain and exhibit striking differences.[60][85][87][89][90][91][92][93] Some 150 years after Alexander (1852)[94] first suggested that the Milky Way was a spiral, there is currently no consensus on the nature of the Milky Way’s spiral arms. Perfect logarithmic spiral patterns only crudely describe features near the Sun,[87][92] because galaxies commonly have arms that branch, merge, twist unexpectedly, and feature a degree of irregularity.[70][92][93] The possible scenario of the Sun within a spur / Local arm[87] emphasizes that point and indicates that such features are probably not unique, and exist elsewhere in the Milky Way.[92]

As in most spiral galaxies, each spiral arm can be described as a logarithmic spiral. Estimates of the pitch angle of the arms range from about 7° to 25°.[95][96] There are thought to be four spiral arms that all start near the Milky Way’s center. These are named as follows, with the positions of the arms shown in the image at right:
Two spiral arms, the Scutum–Centaurus arm and the Carina–Sagittarius arm, have tangent points inside the Sun’s orbit about the center of the Milky Way. If these arms contain an overdensity of stars compared to the average density of stars in the Galactic disk, it would be detectable by counting the stars near the tangent point. Two surveys of near-infrared light, which is sensitive primarily to red giants and not affected by dust extinction, detected the predicted overabundance in the Scutum–Centaurus arm but not in the Carina–Sagittarius arm: the Scutum-Centaurus Arm contains approximately 30% more red giants than would be expected in the absence of a spiral arm.[95][98] In 2008, Robert Benjamin of the University of Wisconsin–Whitewater used this observation to suggest that the Milky Way possesses only two major stellar arms: the Perseus arm and the Scutum–Centaurus arm. The rest of the arms contain excess gas but not excess old stars.[60] In December 2013, astronomers found that the distribution of young stars and star-forming regions matches the four-arm spiral description of the Milky Way.[99][100][101] Thus, the Milky Way appears to have two spiral arms as traced by old stars and four spiral arms as traced by gas and young stars. The explanation for this apparent discrepancy is unclear.[101]

The Near 3 kpc Arm (also called Expanding 3 kpc Arm or simply 3 kpc Arm) was discovered in the 1950s by astronomer van Woerden and collaborators through 21-centimeter radio measurements of HI (atomic hydrogen).[102][103] It was found to be expanding away from the center of the Milky Way at more than 50 km/s. It is located in the fourth galactic quadrant at a distance of about 5.2 kpc from the Sun and 3.3 kpc from the Galactic Center. The Far 3 kpc Arm was discovered in 2008 by astronomer Tom Dame (Harvard-Smithsonian CfA). It’s located in the first galactic quadrant at a distance of 3 kpc (about 10,000 ly) from the Galactic Center.[103][104]

A simulation published in 2011 suggested that the Milky Way may have obtained its spiral arm structure as a result of repeated collisions with the Sagittarius Dwarf Elliptical Galaxy.[105]

It has been suggested that the Milky Way contains two different spiral patterns: an inner one, formed by the Sagittarius arm, that rotates fast and an outer one, formed by the Carina and Perseus arms, whose rotation velocity is slower and whose arms are tightly wound. In this scenario, suggested by numerical simulations of the dynamics of the different spiral arms, the outer pattern would form an outer pseudoring[106] and the two patterns would be connected by the Cygnus arm.[107]

Outside of the major spiral arms is the Monoceros Ring (or Outer Ring), a ring of gas and stars torn from other galaxies billions of years ago. However, several members of the scientific community recently restated their position affirming the Monoceros structure is nothing more than an over-density produced by the flared and warped thick disk of the Milky Way.[108]

Halo
The Galactic disk is surrounded by a spheroidal halo of old stars and globular clusters, of which 90% lie within 100,000 light-years (30 kpc) of the Galactic Center.[109] However, a few globular clusters have been found farther, such as PAL 4 and AM1 at more than 200,000 light-years away from the Galactic Center. About 40% of the Milky Way’s clusters are on retrograde orbits, which means they move in the opposite direction from the Milky Way rotation.[110] The globular clusters can follow rosette orbits about the Milky Way, in contrast to the elliptical orbit of a planet around a star.[111]

Although the disk contains dust that obscures the view in some wavelengths, the halo component does not. Active star formation takes place in the disk (especially in the spiral arms, which represent areas of high density), but does not take place in the halo, as there is little gas cool enough to collapse into stars.[11] Open clusters are also located primarily in the disk.[112]

Discoveries in the early 21st century have added dimension to the knowledge of the Milky Way’s structure. With the discovery that the disk of the Andromeda Galaxy (M31) extends much further than previously thought,[113] the possibility of the disk of the Milky Way Galaxy extending further is apparent, and this is supported by evidence from the discovery of the Outer Arm extension of the Cygnus Arm[97][114] and of a similar extension of the Scutum-Centaurus Arm.[115] With the discovery of the Sagittarius Dwarf Elliptical Galaxy came the discovery of a ribbon of galactic debris as the polar orbit of the dwarf and its interaction with the Milky Way tears it apart. Similarly, with the discovery of the Canis Major Dwarf Galaxy, it was found that a ring of galactic debris from its interaction with the Milky Way encircles the Galactic disk.

On January 9, 2006, Mario Jurić and others of Princeton University announced that the Sloan Digital Sky Survey of the northern sky found a huge and diffuse structure (spread out across an area around 5,000 times the size of a full moon) within the Milky Way that does not seem to fit within current models. The collection of stars rises close to perpendicular to the plane of the spiral arms of the Milky Way. The proposed likely interpretation is that a dwarf galaxy is merging with the Milky Way. This galaxy is tentatively named the Virgo Stellar Stream and is found in the direction of Virgo about 30,000 light-years (9 kpc) away.[116]

Gaseous halo
In addition to the stellar halo, the Chandra X-ray Observatory, XMM-Newton, and Suzaku have provided evidence that there is a gaseous halo with a large amount of hot gas. The halo extends for hundreds of thousand of light years, much further than the stellar halo and close to the distance of the Large and Small Magellanic Clouds. The mass of this hot halo is nearly equivalent to the mass of the Milky Way itself.[117][118][119] The temperature of this halo gas is between 1 million and 2.5 million kelvin, a few hundred times hotter than the surface of the sun.[120]

Observations of distant galaxies indicate that the Universe had about one-sixth as much baryonic (ordinary) matter as dark matter when it was just a few billion years old. However, only about half of those baryons are accounted for in the modern Universe based on observations of nearby galaxies like the Milky Way.[121] If the finding that the mass of the halo is comparable to the mass of the Milky Way is confirmed, it could be the identity of the missing baryons around the Milky Way.

The Sun is near the inner rim of the Orion Arm, within the Local Fluff of the Local Bubble, and in the Gould Belt, at a distance of 8.33 ± 0.35 kiloparsecs (27,200 ± 1,100 ly) from the Galactic Center.[10][67][122] The Sun is currently 5–30 parsecs (16–98 ly) from the central plane of the Galactic disk.[123] The distance between the local arm and the next arm out, the Perseus Arm, is about 2,000 parsecs (6,500 ly).[124] The Sun, and thus the Solar System, is found in the Galactic habitable zone.

There are about 208 stars brighter than absolute magnitude 8.5 within a sphere with a radius of 15 parsecs (49 ly) from the Sun, giving a density of one star per 69 cubic parsec, or one star per 2,360 cubic light-year (from List of nearest bright stars). On the other hand, there are 64 known stars (of any magnitude, not counting 4 brown dwarfs) within 5 parsecs (16 ly) of the Sun, giving a density of about one star per 8.2 cubic parsec, or one per 284 cubic light-year (from List of nearest stars). This illustrates the fact that there are far more faint stars than bright stars: in the entire sky, there are about 500 stars brighter than apparent magnitude 4 but 15.5 million stars brighter than apparent magnitude 14.[125]

The apex of the Sun’s way, or the solar apex, is the direction that the Sun travels through space in the Milky Way. The general direction of the Sun’s Galactic motion is towards the star Vega near the constellation of Hercules, at an angle of roughly 60 sky degrees to the direction of the Galactic Center. The Sun’s orbit about the Milky Way is expected to be roughly elliptical with the addition of perturbations due to the Galactic spiral arms and non-uniform mass distributions. In addition, the Sun oscillates up and down relative to the Galactic plane approximately 2.7 times per orbit. This is very similar to how a simple harmonic oscillator works with no drag force (damping) term. These oscillations were until recently thought to coincide with mass lifeform extinction periods on Earth.[126] However, a reanalysis of the effects of the Sun’s transit through the spiral structure based on CO data has failed to find a correlation.[127]

It takes the Solar System about 240 million years to complete one orbit of the Milky Way (a Galactic year),[11] so the Sun is thought to have completed 18–20 orbits during its lifetime and 1/1250 of a revolution since the origin of humans. The orbital speed of the Solar System about the center of the Milky Way is approximately 220 km/s or 0.073% of the speed of light. At this speed, it takes around 1,400 years for the Solar System to travel a distance of 1 light-year, or 8 days to travel 1 AU (astronomical unit).

The stars and gas in the Milky Way rotate about its center differentially, meaning that the rotation period varies with location. As is typical for spiral galaxies, the orbital speed of most stars in the Milky Way does not depend strongly on their distance from the center. Away from the central bulge or outer rim, the typical stellar orbital speed is between 210 and 240 km/s.[131] Hence the orbital period of the typical star is directly proportional only to the length of the path traveled. This is unlike the situation within the Solar System, where two-body gravitational dynamics dominate and different orbits have significantly different velocities associated with them. The rotation curve (shown in the figure) describes this rotation. Toward the center of the Milky Way the orbit speeds are too low, whereas beyond 7 kpcs the speeds are too high to match what would be expected from the universal law of gravitation.

If the Milky Way contained only the mass observed in stars, gas, and other baryonic (ordinary) matter, the rotation speed would decrease with distance from the center. However, the observed curve is relatively flat, indicating that there is additional mass that cannot be detected directly with electromagnetic radiation. This inconsistency is attributed to dark matter.[25] The rotation curve of the Milky Way agrees with the universal rotation curve of spiral galaxies, the strongest proof of the existence of dark matter in galaxies. Alternatively, a minority of astronomers propose that a modification of the law of gravity may explain the observed rotation curve.
The Milky Way began as one or several small overdensities in the mass distribution in the Universe shortly after the Big Bang. Some of these overdensities were the seeds of globular clusters in which the oldest remaining stars in what is now the Milky Way formed. These stars and clusters now comprise the stellar halo of the Milky Way. Within a few billion years of the birth of the first stars, the mass of the Milky Way was large enough so that it was spinning relatively quickly. Due to conservation of angular momentum, this led the gaseous interstellar medium to collapse from a roughly spheroidal shape to a disk. Therefore, later generations of stars formed in this spiral disk. Most younger stars, including the Sun, are observed to be in the disk.[133][134]

Since the first stars began to form, the Milky Way has grown through both galaxy mergers (particularly early in the Milky Way’s growth) and accretion of gas directly from the Galactic halo.[134] The Milky Way is currently accreting material from two of its nearest satellite galaxies, the Large and Small Magellanic Clouds, through the Magellanic Stream. Direct accretion of gas is observed in high-velocity clouds like the Smith Cloud.[135][136] However, properties of the Milky Way such as stellar mass, angular momentum, and metallicity in its outermost regions suggest it has undergone no mergers with large galaxies in the last 10 billion years. This lack of recent major mergers is unusual among similar spiral galaxies; its neighbour the Andromeda Galaxy appears to have a more typical history shaped by more recent mergers with relatively large galaxies.[137][138]

According to recent studies, the Milky Way as well as Andromeda lie in what in the galaxy color–magnitude diagram is known as the green valley, a region populated by galaxies in transition from the blue cloud (galaxies actively forming new stars) to the red sequence (galaxies that lack star formation). Star-formation activity in green valley galaxies is slowing as they run out of star-forming gas in the interstellar medium. In simulated galaxies with similar properties, star formation will typically have been extinguished within about five billion years from now, even accounting for the expected, short-term increase in the rate of star formation due to the collision between both the Milky Way and the Andromeda Galaxy.[139] In fact, measurements of other galaxies similar to the Milky Way suggest it is among the reddest and brightest spiral galaxies that are still forming new stars and it is just slightly bluer than the bluest red sequence galaxies.[140]

Age[edit] The ages of individual stars in the Milky Way can be estimated by measuring the abundance of long-lived radioactive elements such as thorium-232 and uranium-238, then comparing the results to estimates of their original abundance, a technique called nucleocosmochronology. These yield values of about 12.5 ± 3 billion years for CS 31082-001[141] and 13.8 ± 4 billion years for BD +17° 3248.[142] Once a white dwarf is formed, it begins to undergo radiative cooling and the surface temperature steadily drops. By measuring the temperatures of the coolest of these white dwarfs and comparing them to their expected initial temperature, an age estimate can be made. With this technique, the age of the globular cluster M4 was estimated as 12.7 ± 0.7 billion years. Globular clusters are among the oldest objects in the Milky Way Galaxy, which thus set a lower limit on the age of the Milky Way. Age estimates of the oldest of these clusters gives a best fit estimate of 12.6 billion years, and a 95% confidence upper limit of 16 billion years.[143]

In 2007, a star in the galactic halo, HE 1523-0901, was estimated to be about 13.2 billion years old, ≈0.5 billion years less than the age of the universe. As the oldest known object in the Milky Way at that time, this measurement placed a lower limit on the age of the Milky Way.[144] This estimate was determined using the UV-Visual Echelle Spectrograph of the Very Large Telescope to measure the relative strengths of spectral lines caused by the presence of thorium and other elements created by the R-process. The line strengths yield abundances of different elemental isotopes, from which an estimate of the age of the star can be derived using nucleocosmochronology.[144]

The age of stars in the galactic thin disk has also been estimated using nucleocosmochronology. Measurements of thin disk stars yield an estimate that the thin disk formed 8.8 ± 1.7 billion years ago. These measurements suggest there was a hiatus of almost 5 billion years between the formation of the galactic halo and the thin disk.
The Milky Way and the Andromeda Galaxy are a binary system of giant spiral galaxies belonging to a group of 50 closely bound galaxies known as the Local Group, itself being part of the Virgo Supercluster. The Virgo Supercluster forms part of a greater structure, called Laniakea.[146]

Two smaller galaxies and a number of dwarf galaxies in the Local Group orbit the Milky Way. The largest of these is the Large Magellanic Cloud with a diameter of 14,000 light-years. It has a close companion, the Small Magellanic Cloud. The Magellanic Stream is a stream of neutral hydrogen gas extending from these two small galaxies across 100° of the sky. The stream is thought to have been dragged from the Magellanic Clouds in tidal interactions with the Milky Way.[147] Some of the dwarf galaxies orbiting the Milky Way are Canis Major Dwarf (the closest), Sagittarius Dwarf Elliptical Galaxy, Ursa Minor Dwarf, Sculptor Dwarf, Sextans Dwarf, Fornax Dwarf, and Leo I Dwarf. The smallest Milky Way dwarf galaxies are only 500 light-years in diameter. These include Carina Dwarf, Draco Dwarf, and Leo II Dwarf. There may still be undetected dwarf galaxies that are dynamically bound to the Milky Way, as well as some that have already been absorbed by the Milky Way, such as Omega Centauri.

In January 2006, researchers reported that the heretofore unexplained warp in the disk of the Milky Way has now been mapped and found to be a ripple or vibration set up by the Large and Small Magellanic Clouds as they orbit the Milky Way, causing vibrations when they pass through its edges. Previously, these two galaxies, at around 2% of the mass of the Milky Way, were considered too small to influence the Milky Way. However, in a computer model, the movement of these two galaxies creates a dark matter wake that amplifies their influence on the larger Milky Way.[148]

Current measurements suggest the Andromeda Galaxy is approaching us at 100 to 140 kilometers per second. In 3 to 4 billion years, there may be an Andromeda–Milky Way collision, depending on the importance of unknown lateral components to the galaxies’ relative motion. If they collide, the chance of individual stars colliding with each other is extremely low, but instead the two galaxies will merge to form a single elliptical galaxy or perhaps a large disk galaxy[149] over the course of about a billion years.[150]

Velocity
Although special relativity states that there is no "preferred" inertial frame of reference in space with which to compare the Milky Way, the Milky Way does have a velocity with respect to cosmological frames of reference.

One such frame of reference is the Hubble flow, the apparent motions of galaxy clusters due to the expansion of space. Individual galaxies, including the Milky Way, have peculiar velocities relative to the average flow. Thus, to compare the Milky Way to the Hubble flow, one must consider a volume large enough so that the expansion of the Universe dominates over local, random motions. A large enough volume means that the mean motion of galaxies within this volume is equal to the Hubble flow. Astronomers believe the Milky Way is moving at approximately 630 km per second with respect to this local co-moving frame of reference.[151] The Milky Way is moving in the general direction of the Great Attractor and other galaxy clusters, including the Shapley supercluster, behind it.[152] The Local Group (a cluster of gravitationally bound galaxies containing, among others, the Milky Way and the Andromeda Galaxy) is part of a supercluster called the Local Supercluster, centered near the Virgo Cluster: although they are moving away from each other at 967 km/s as part of the Hubble flow, this velocity is less than would be expected given the 16.8 million pc distance due to the gravitational attraction between the Local Group and the Virgo Cluster.[153]

Another reference frame is provided by the cosmic microwave background (CMB). The Milky Way is moving at 552 ± 6 km/s[13] with respect to the photons of the CMB, toward 10.5 right ascension, −24° declination (J2000 epoch, near the center of Hydra). This motion is observed by satellites such as the Cosmic Background Explorer (COBE) and the Wilkinson Microwave Anisotropy Probe (WMAP) as a dipole contribution to the CMB, as photons in equilibrium in the CMB frame get blue-shifted in the direction of the motion and red-shifted in the opposite direction.[13]

Etymology and mythology
Main articles: List of names for the Milky Way and Milky Way (mythology)
In western culture the name "Milky Way" is derived from its appearance as a dim un-resolved "milky" glowing band arching across the night sky. The term is a translation of the Classical Latin via lactea, in turn derived from the Hellenistic Greek γαλαξίας, short for γαλαξίας κύκλος (pr. galaktikos kyklos, "milky circle"). The Ancient Greek γαλαξίας (galaxias), from root γαλακτ-, γάλα (milk) + -ίας (forming adjectives), is also the root of "galaxy", the name for our, and later all such, collections of stars.[18][154][155][156] The Milky Way "milk circle" was just one of 11 circles the Greeks identified in the sky, others being the zodiac, the meridian, the horizon, the equator, the tropics of Cancer and Capricorn, Arctic and Antarctic circles, and two colure circles passing through both poles.

In Meteorologica (DK 59 A80), Aristotle (384–322 BC) wrote that the Greek philosophers Anaxagoras (ca. 500–428 BC) and Democritus (460–370 BC) proposed that the Milky Way might consist of distant stars. However, Aristotle himself believed the Milky Way to be caused by "the ignition of the fiery exhalation of some stars which were large, numerous and close together" and that the "ignition takes place in the upper part of the atmosphere, in the region of the world which is continuous with the heavenly motions."[158] The Neoplatonist philosopher Olympiodorus the Younger (c. 495–570 A.D.) criticized this view, arguing that if the Milky Way were sublunary it should appear different at different times and places on Earth, and that it should have parallax, which it does not. In his view, the Milky Way was celestial. This idea would be influential later in the Islamic world.[159]

The Persian astronomer Abū Rayhān al-Bīrūnī (973–1048) proposed that the Milky Way is "a collection of countless fragments of the nature of nebulous stars".[160] The Andalusian astronomer Avempace (d. 1138) proposed the Milky Way to be made up of many stars but appears to be a continuous image due to the effect of refraction in the Earth’s atmosphere, citing his observation of a conjunction of Jupiter and Mars in 1106 or 1107 as evidence.[158] Ibn Qayyim Al-Jawziyya (1292–1350) proposed that the Milky Way is "a myriad of tiny stars packed together in the sphere of the fixed stars" and that these stars are larger than planets.[161]

According to Jamil Ragep, the Persian astronomer Naṣīr al-Dīn al-Ṭūsī (1201–1274) in his Tadhkira writes: "The Milky Way, i.e. the Galaxy, is made up of a very large number of small, tightly clustered stars, which, on account of their concentration and smallness, seem to be cloudy patches. Because of this, it was likened to milk in color."[162]

Actual proof of the Milky Way consisting of many stars came in 1610 when Galileo Galilei used a telescope to study the Milky Way and discovered that it was composed of a huge number of faint stars.[163][164] In a treatise in 1755, Immanuel Kant, drawing on earlier work by Thomas Wright,[165] speculated (correctly) that the Milky Way might be a rotating body of a huge number of stars, held together by gravitational forces akin to the Solar System but on much larger scales.[166] The resulting disk of stars would be seen as a band on the sky from our perspective inside the disk. Kant also conjectured that some of the nebulae visible in the night sky might be separate "galaxies" themselves, similar to our own. Kant referred to both the Milky Way and the "extragalactic nebulae" as "island universes", a term still current up to the 1930s.[167][168][169]

The first attempt to describe the shape of the Milky Way and the position of the Sun within it was carried out by William Herschel in 1785 by carefully counting the number of stars in different regions of the visible sky. He produced a diagram of the shape of the Milky Way with the Solar System close to the center.[170]

In 1845, Lord Rosse construct

Posted by !!! Painting with Light !!! #schauer on 2014-10-19 14:40:33

Tagged: , Schauer , Christian , Oberdiendorf , Passau , Hauzenberg , Painting , with , Licht , Bayern , Bavaria , Germany , Europe , Canon , Tamron , Nikon , Lightroom , Photoshop , Milkyway , Milchstraße , Street , Road , Highway , Nature , Landscape , Building , Nacht , Night , Nuit , Noir , Dark , Sky , Heaven , Cloud , Star , ISO , Long , Exposure , Life , Live , Crane , Kran , Vehicle , Milf , Car , Blue , Midnight , Bau , Cold , Airplane , Plane , Flugzeug , Trail , Baum , Tree , Moon , No , Non , High , Highlight , Low , Upper , Welt , World

The colorful harvest

The colorful harvest

Die Äpfel (Malus) bilden eine Pflanzengattung der Kernobstgewächse (Pyrinae) aus der Familie der Rosengewächse (Rosaceae). Die Gattung umfasst etwa 42 bis 55 Arten laubwerfender Bäume und Sträucher aus Wäldern und Dickichten der nördlichen gemäßigten Zone in Europa, Asien und Nordamerika, aus denen auch eine große Anzahl an oft schwer unterscheidbaren Hybriden hervorgegangen ist.

Die weltweit mit Abstand bekannteste und wirtschaftlich sehr bedeutende Art ist der Kulturapfel (Malus domestica). Daneben werden manche aus Ostasien stammende Arten mit nur etwa kirschgroßen Früchten, wie etwa der Japanische Apfel (Malus floribunda), der Kirschapfel (Malus baccata) und Malus ×zumi in gemäßigten Klimagebieten als Ziersträucher und -bäume angepflanzt. Nicht zu verwechseln mit den Äpfeln sind die nicht näher verwandten Granatäpfel (Punica granatum).
Das Wort Apfel wird auf die urindogermanische Form *h₂ébōl zurückgeführt, die nur Fortsetzungen im westlichen indogermanischen Sprachgebiet (Germanisch, Keltisch, Baltisch und Slawisch) hat und dort in allen Formen den Apfel bezeichnet. In der Forschung herrscht Uneinigkeit darüber, wie die Form genau anzusetzen ist und ob es sich um das urindogermanische Apfelwort handelt oder eine Entlehnung aus einer anderen Sprache. Aus der Akkusativform urindogermanisch *h₂ébl-ṃ > urgermanisch *ablun entwickelt sich das urgermanisches Apfelwort *ablus, aus dem (mit weiterer grammatikalischer Umgestaltung) althochdeutsch apful > Apfel (Mehrzahl epfili > Äpfel), altenglisch æppel > apple, isländisch epli hervorgehen.
Habitus und Belaubung
Die Arten der Gattung Äpfel (Malus) sind sommergrüne Bäume oder Sträucher. Sie sind meist unbewehrt. Die wechselständig angeordneten Laubblätter sind gestielt. Die einfache Blattspreite ist oval bis eiförmig oder elliptisch. Die Blattränder sind meist gesägt, selten glatt und manchmal gelappt. Einige Arten bzw. Sorten werden wegen ihres purpurnen Laubes im Herbst geschätzt. Nebenblätter sind vorhanden, verwelken aber oft früh.

Blütenstände und Blüten
Die gestielten Blüten der Apfelbäume stehen einzeln oder in doldigen schirmrispigen Blütenständen. Die fünfzähligen, zwittrigen, radiärsymmetrischen Blüten sind meist flach becherförmig und weisen meist einen Durchmesser von 2 bis 5 cm auf. Häufig duften die Blüten. Die Blütenachse ist krugförmig. Die fünf grünen Kelchblätter sind auch noch an den Früchten erhalten. Die fünf freien Kronblätter sind weiß, rosa oder rot. In jeder Blüte sind viele (15 bis 50) Staubblätter vorhanden, mit weißen Staubfäden und gelben Staubbeuteln. Aus drei bis fünf Fruchtblättern besteht der unterständige Fruchtknoten. Die drei bis fünf Griffel sind nur an ihrer Basis verwachsen. Bei einigen Züchtungen sind die Blüten, durch Umwandlung der Staubblätter in kronblattähnliche Blütenblätter, halbgefüllt oder gefüllt.
Gemeinhin bekannt sind die mehr oder minder rundlichen, essbaren Früchte. Bei einigen Arten sind sie roh ungenießbar. Das fleischige Gewebe, das normalerweise als Frucht bezeichnet wird, entsteht nicht aus dem Fruchtknoten, sondern aus der Blütenachse; der Biologe spricht daher von Scheinfrüchten. Genauer ist die Apfelfrucht eine Sonderform der Sammelbalgfrucht. Ein Balg besteht aus einem Fruchtblatt, das mit sich selbst verwächst. Innerhalb des Fruchtfleisches entsteht aus dem balgähnlichen Fruchtblatt ein pergamentartiges Gehäuse. Im Fruchtfleisch selbst sind höchstens noch vereinzelt Steinzellennester enthalten. Die Samen sind braun oder schwarz; sie enthalten geringe Mengen an giftigen Cyaniden.
Die Gattung Malus gehört zur Subtribus Pyrinae der Tribus Pyreae in der Unterfamilie Spiraeoideae innerhalb der Familie Rosaceae. Der Gattungsname Malus wurde 1754 durch Philip Miller in Gard. Dict. Abr., 4. Auflage, S. 835, erstveröffentlicht. Synonyme für Malus Mill. sind Docyniopsis (C.K.Schneid.) Koidz., Eriolobus (DC.) M.Roem.[2]

Es gibt etwa 42 bis 55 Malus-Arten; hier eine Auflistung mit Heimatangaben. Zu den bekannten Sorten der fruchtliefernden Apfelbäume siehe Kulturapfel und Apfelsorten. In China sind etwa 25 Arten zu finden, davon 15 nur dort. Die Gattung Malus wird in (sechs[2] bis) acht Sektionen (2006 und 2008 zwei dazu gekommen) gegliedert:

Sektion Chloromeles: Mit nur noch drei gültigen Arten nur in Nordamerika:
Südlicher Wildapfel (Malus angustifolia (Aiton) Michx.): Heimat sind die USA.
Süßer Wildapfel (Malus coronaria (L.) Mill., Syn.: Malus bracteata Rehder, Malus coronaria var. dasycalyx Rehder, Malus fragrans Rehder, Malus glabrata Rehder, Malus glaucescens Rehder, Malus lancifolia Rehder, Pyrus coronaria L.): Heimat ist das östliche Nordamerika.
Savannen- oder Prärie-Wildapfel Malus ioensis (Alph.Wood) Britton: Heimat ist das westliche Nordamerika.
Sektion Docyniopsis: Mit nur vier Arten in Asien:
Malus doumeri (Bois) A.Chev. (Syn.: Malus formosana Kawak. & Koidz., Malus laosensis (Cardot) A.Chev., Pyrus doumeri Bois): Heimat ist China, Taiwan, Laos und Vietnam.
Malus leiocalyca S.Z.Huang: Heimat ist China.
Malus melliana (Hand.-Mazz.) Rehder: Heimat ist China.
Wollapfel (Malus tschonoskii (Maxim.) C.K.Schneid.): Heimat ist Japan.
Sektion Eriolobus (Seringe) C.K.Schneid.: Mit der einzigen Art:
Malus trilobata (Poir.) C.K.Schneid.: Die Heimat ist Kleinasien: Griechenland, Syrien, Libanon, Israel.
Sektion Florentinae Cheng et al.:[3] Malus florentina (Zuccagni) C.K.Schneid. (Syn.: Malus crataegifolia (Savi) Koehne)
Sektion Gymnomeles: Mit etwa sechs Arten:
Kirschapfel, auch Sibirischer Wildapfel oder Beerenapfel genannt (Malus baccata) (L.) Borkh. (Syn: Malus pallasiana Juz., Malus sibirica (Maxim.) Kom., Malus daochengensis C.L.Li, Malus rockii Rehder, Malus jinxianensis J.Q.Deng & J.Y.Hong, Malus xiaojinensis M.H.Cheng & N.G.Jiang): Heimat ist Ostasien.
Halls Apfel (Malus halliana Koehne): Heimat ist Japan und China.
Teeapfel oder Chinesischer Wildapfel (Malus hupehensis (Pamp.)) Rehder: Heimat ist China.
Malus mandshurica (Maxim.) Kom. ex Skvortsov (Syn: Malus cerasifera Spach, Malus sachalinensis Juz., Pyrus baccata var. mandshurica Maxim., Malus baccata ssp. mandshurica (Komarov) Likhonos, M. baccata var. mandshurica (Maxim.) C.K.Schneider): Heimat ist Ostasien.
Malus sikkimensis (Wenz.) Koehne ex C.K.Schneid.: Heimat ist der Himalaja.
Malus spontanea (Makino) Makino
Sektion Malus: Mit etwa elf Arten und einigen Hybriden:
Malus chitralensis Vassilcz.
Japanischer Wildapfel, auch Korallenapfel genannt (Malus floribunda Sieb. ex Van Houtte): Heimat ist Japan.
Malus muliensis T.C.Ku
Kaukasusapfel oder Orientalischer Apfel (Malus orientalis Uglitzk.), Bergwälder und Waldränder des südlichen Kaukasus – Neben M. sieversii zweitwichtigster Vorfahre des Kulturapfels
Malus prunifolia (Willd.) Borkh.: Heimat ist China.
Malus pumila Mill. (Syn.: Malus communis Poiret, M. dasyphylla Borkhausen, M. dasyphylla var. domestica Koidzumi, M. domestica Borkhausen, M. domestica subsp. pumila (Mill.) Likhonos, M. pumila var. domestica C.K.Schneider, Niedzwetzki-Apfel M. niedzwetzkyana Dieck ex Koehne, M. sylvestris ssp. mitis Mansfeld, Pyrus malus L., P. malus var. pumila Henry), (westliches Asien, Zentralasien und Osteuropa)
Asiatischer Wildapfel, auch Altai-Apfel (Malus sieversii (Ledeb.) M.Roem., Syn.: Malus kirghisorum Al.Fed. & Fed., Malus turkmenorum Juz. & Popov), Bergwälder Zentralasiens von Tadschikistan bis Westchina – wahrscheinlich Hauptstammform des Kulturapfels.
Chinesischer Apfel (Malus spectabilis (Aiton) Borkh.), (Asien, wahrscheinlich China)
Holzapfel oder Europäischer Wildapfel genannt (Malus sylvestris (L.) Mill.), westliches Asien und Europa – nach neuesten Untersuchungen vermutlich keine Stammform des Kulturapfels, jedoch möglicherweise darin eingekreuzt.
Malus zhaojiaoensis N.G.Jiang
Malus ×adstringens Zabel (= M. baccata × M. pumila)
Malus ×arnoldiana (Rehder) Sarg. ex Rehder (= M. baccata × M. floribunda, Syn.: Malus floribunda var. arnoldiana Rehder)
Malus ×asiatica Nakai (Syn.: Malus ringo Sieb. ex Carrière): Heimat ist China, dort gibt es viele Sorten für den Fruchtanbau.
Malus ×astracanica hort. ex Dum. Cours. (= M. prunifolia × M. pumila)
Kulturapfel (Malus domestica Borkh.), der Ursprung liegt in Asien. Die Stammformen sind wahrscheinlich der Asiatischer Wildapfel (M. sieversii) und der Kaukasusapfel (M. orientalis). Zudem werden frühe Kreuzungen mit M. dasyphylia und M. praecox angenommen.
Malus ×hartwigii Koehne (= M. baccata × M. halliana)
Malus ×magdeburgensis Hartwig (= M. pumila × M. spectabilis), (Deutschland, Zufallsfund in der Nähe von Magdeburg)
Malus ×micromalus Makino (= M. spectabilis × M. baccata): Wird in China weitverbreitet als Ziergehölz und auf Grund der essbaren Früchte angebaut.
Purpurapfel (Malus ×purpurea (A.Barbier) Rehder, = M. ×atrosanguinea × M. pumila, Syn.: Malus floribunda var. lemoinei É.Lemoine, Malus floribunda var. purpurea A.Barbier, Malus ×purpurea f. eleyi (Bean) Rehder, Malus ×purpurea f. lemoinei (É.Lemoine) Rehder, Malus ×purpurea var. aldenhamensis Rehder)
Malus ×robusta (Carrière) Rehder (= M. baccata × M. prunifolia, Syn.: Malus microcarpa var. robusta Carrière)
Malus ×scheideckeri Späth ex Zabel (= M. floribunda × M. prunifolia)
Sektion Sorbomalus (Zabel) C.K.Schneid.
Malus bhutanica (W.W.Sm.) J.B.Phipps (Syn.: Malus toringoides (Rehder) Hughes)
Oregon-Wildapfel (Malus fusca) (Raf.) C.K.Schneid. (Syn.: Malus diversifolia (Bong.) M.Roem., Malus rivularis (Douglas) M.Roem.), (nordwestliches Nordamerika)
Malus kansuensis (Batalin) C.K.Schneid.: Heimat ist das westliche China.
Malus komarovii (Sarg.) Rehder: Heimat ist China und das nördliche Korea
Malus maerkangensis M.H.Cheng et al.
Malus sargentii Rehder, (Japan)
Malus toringo (Sieb.) de Vriese (Syn.: Malus sieboldii (Regel) Rehder), (östliches Asien, Japan)
Malus transitoria (Batalin) C.K.Schneid. (Syn.: Malus bhutanica (W W.Sm.) J.B.Phipps), (nordwestliches China)
Zierapfel (Malus ×zumi (Matsum.) Rehder), keine Wildform bekannt; es gibt mehrere Sorten, zum Teil mit blutroten Blättern.
Malus ×atrosanguinea (hort. ex Späth) C.K.Schneid. (= M. halliana × M. toringo)
Sektion Yunnanenses (Rehd.) G.Z.Qian:[4] Mit nur vier Arten, die nur in China vorkommen:
Malus honanensis Rehder: Heimat ist China.
Malus ombrophila Hand.-Mazz.: Heimat ist China.
Malus prattii (Hemsl.) C.K.Schneider (Syn.: Malus kaido Dippel): Heimat sind nur die chinesischen Provinzen: westliches Sichuan und nordwestliches Yunnan
Malus yunnanensis (Franch.) C.K.Schneid.: Heimat ist das südwestliche China.
ohne Tribuszugehörigkeit:
Malus brevipes (Rehder) Rehder (ist nur aus Kultur bekannt)
Malus ×platycarpa Rehder (USA)
Malus ×sublobata (Dippel) Rehder (= M. prunifolia × M. toringo, Syn.: Malus ringo var. sublobata Dippel)
Malus ×soulardi
Es gibt auch Gattungskreuzungen innerhalb des Untertribus Pyrinae, zum Beispiel Sorbus × Malus und sogar Dreifachkreuzungen: (Cydonia × Pyrus) × Malus.
Malus (/ˈmeɪləs/[3] or /ˈmæləs/), apple, is a genus of about 30–55 species[4] of small deciduous trees or shrubs in the family Rosaceae, including the domesticated orchard apple (M. domestica). The other species are generally known as crabapples, crab apples, crabs, or wild apples.

The genus is native to the temperate zone of the Northern Hemisphere.
Apple trees are typically 4–12 m (13–39 ft) tall at maturity, with a dense, twiggy crown. The leaves are 3–10 cm (1.2–3.9 in) long, alternate, simple, with a serrated margin. The flowers are borne in corymbs, and have five petals, which may be white, pink or red, and are perfect, with usually red stamens that produce copious pollen, and a half-inferior ovary; flowering occurs in the spring after 50–80 growing degree days (varying greatly according to subspecies and cultivar).

Apples require cross-pollination between individuals by insects (typically bees, which freely visit the flowers for both nectar and pollen); all are self-sterile, and (with the exception of a few specially developed cultivars) self-pollination is impossible, making pollinating insects essential. Several Malus species, including domestic apples, hybridize freely.[6] They are used as food plants by the larvae of a large number of Lepidoptera species; see list of Lepidoptera that feed on Malus.

The fruit is a globose pome, varying in size from 1–4 cm (0.39–1.57 in) diameter in most of the wild species, to 6 cm (2.4 in) in M. sylvestris sieversii, 8 cm (3.1 in) in M. domestica, and even larger in certain cultivated orchard apples. The centre of the fruit contains five carpels arranged star-like, each containing one or two seeds.

For the Malus domestica cultivars, the cultivated apples, see Apple.

Crabapples are popular as compact ornamental trees, providing blossom in Spring and colourful fruit in Autumn. The fruits often persist throughout Winter. Numerous hybrid cultivars have been selected, of which ‘Evereste'[7] and ‘Red Sentinel'[8] have gained The Royal Horticultural Society’s Award of Garden Merit.

Other varieties are dealt with under their species names.

Some crabapples are used as rootstocks for domestic apples to add beneficial characteristics.[9] For example, varieties of Baccata, also called Siberian crab, rootstock is used to give additional cold hardiness to the combined plant for orchards in cold northern areas.[10]

They are also used as pollinizers in apple orchards. Varieties of crabapple are selected to bloom contemporaneously with the apple variety in an orchard planting, and the crabs are planted every sixth or seventh tree, or limbs of a crab tree are grafted onto some of the apple trees. In emergencies, a bucket or drum bouquet of crabapple flowering branches are placed near the beehives as orchard pollenizers. See also Fruit tree pollination. Because of the plentiful blossoms and small fruit, crabapples are popular for use in bonsai culture.

Crabapple fruit is not an important crop in most areas, being extremely sour and (in some species) woody, and is rarely eaten raw for this reason. In some southeast Asian cultures they are valued as a sour condiment, sometimes eaten with salt and chilli pepper, or shrimp paste.

Some crabapples varieties are an exception to the reputation of being sour, and can be very sweet, such as the ‘Chestnut’ cultivar.[11]

Crabapples are an excellent source of pectin, and their juice can be made into a ruby-coloured preserve with a full, spicy flavour.[12] A small percentage of crabapples in cider makes a more interesting flavour.[13] As Old English Wergulu, the crab apple is one of the nine plants invoked in the pagan Anglo-Saxon Nine Herbs Charm, recorded in the 10th century.

Apple wood gives off a pleasant scent when burned, and smoke from an apple wood fire gives an excellent flavour to smoked foods.[14] It is easier to cut when green; dry apple wood is exceedingly difficult to carve by hand.[14] It is a good wood for cooking fires because it burns hot and slow, without producing much flame.[14]

Crabapple has been listed as one of the 38 plants that are used to prepare Bach flower remedies,[15] a kind of alternative medicine promoted for its effect on health. However according to Cancer Research UK, "there is no scientific evidence to prove that flower remedies can control, cure or prevent any type of disease, including cancer".
Quelle:
en.wikipedia.org/wiki/Malus
de.wikipedia.org/wiki/%C3%84pfel
Apfelsaft (in der Schweiz und Österreich auch Süßmost) ist ein Fruchtsaft, der durch Pressung von Äpfeln gewonnen wird. Aus 1,5 kg Äpfeln kann ca. 1 Liter Apfelsaft gewonnen werden. Im großen Maßstab geschieht dies in Keltereien. Als Apfelschorle wird er mit Mineralwasser verdünnt getrunken. 2013 betrug in Deutschland der Pro-Kopf-Verbrauch an Apfelsaft 8,4 Liter und an Apfelsaftschorle 8,5 Liter.
Nach dem Pressen ist der Apfelsaft immer naturtrüb, d. h. fruchtfleischhaltig. Zentrifugiert und gefiltert erhält man den klaren Apfelsaft. Beide Varianten – naturtrüb und klar – werden durch Pasteurisation haltbar gemacht. Dabei wird der Saft kurz auf ca. 85 °C erhitzt, um Mikroorganismen abzutöten und die Gärung zu verhindern. Da der naturtrübe Apfelsaft nicht gefiltert wurde, befinden sich in ihm noch die Schwebstoffe. Sie lassen den Saft undurchsichtig erscheinen. Da sie schwerer sind als Wasser, setzen sie sich am Boden ab und sollten vor dem Trinken aufgeschüttelt werden. Aufgrund der in den Schwebstoffen enthaltenen Antioxidantien – es handelt sich hauptsächlich um Polyphenole – enthält naturtrüber Apfelsaft mehr sekundäre Pflanzenstoffe als gefilterter Saft.[2] In Tierversuchen entwickelten Mäuse und Ratten, denen Apfelsaft verabreicht wurde, bis zu 50 % weniger Tumoren, als die Vergleichsgruppe ohne die Apfelsaftgaben.[3][4] Der trübe Apfelsaft war in diesen Versuchen wirksamer als der klare.[5] Vermutlich sind hier die Procyanidine, die in trübem Apfelsaft in hoher Konzentration enthalten sind, die Ursache.[6] Darüber hinaus schmeckt der naturtrübe Apfelsaft meist auch natürlicher und kräftiger als der schwebstofffreie klare Saft. Sortenreine Apfelsäfte, die nur aus einer Apfelsorte gewonnen werden, erweitern die Angebotspalette an Apfelsaft mit einer hohen geschmacklichen Vielfalt.

Zur Herstellung von klarem Apfelsaft wird überwiegend Apfelsaftkonzentrat verwendet. Apfelsaftkonzentrat erhält man durch Entzug von Wasser und Abtrennen von Aromen. Dadurch reduziert sich das Volumen auf ca. ein Sechstel, sodass die Lagerung und der Transport günstiger werden. Durch Hinzufügen von speziell aufbereitetem Trinkwasser und den getrennt gelagerten Aromen erreicht man ein zum ursprünglichen Ausgangsprodukt gleichartiges Produkt. In der Fachsprache nennt sich das rekonstituieren. Die Verarbeitung von Apfelsaftkonzentrat bringt zusätzlich den Vorteil, durch Verschneiden (Mischen) unterschiedlich ausgeprägter Apfelsaftkonzentrate (süße/saure) einen gleichbleibenden Geschmack zu erreichen. Ansonsten würden je nach Apfelsorte und/oder Anbaugebiet unterschiedliche Geschmacksrichtungen im Apfelsaft auftreten.

Die Verfahren des Wasserentzuges und der Rückverdünnung beeinträchtigen auf modernen Konzentratanlagen den Geschmack und den Vitamingehalt kaum. In der deutschen Fruchtsaftverordnung (FrSaftV 2004) und in den Fruchtsaftrichtlinien der EU muss der rückverdünnte Saft gleichartige organoleptische und analytische Eigenschaften aufweisen wie ein nicht aus Konzentrat hergestellter Saft (Direktsaft) aus frischen Früchten derselben Art. Die analytische Gleichartigkeit der nicht flüchtigen Hauptinhaltsstoffe kann über Grad Brix, Zuckerspektrum, Aminosäurespektrum und Mineralstoffe beurteilt werden. Kennzahlen zur Beurteilung sind im AIJN Code of Practice[7] beschrieben. Für die Beurteilung der analytischen Gleichartigkeit des Apfelsaftaromas wird ein Aromaindex Apfel ermittelt.

Apfelsaft dient auch als Vorprodukt für Apfelwein (Cidre, Viez, Most), Apfelkraut und Apfelessig; darüber hinaus wird er auch zur Herstellung von Spirituosen, wie Obstbrand, Apfelkorn oder des bekannten Calvados verwendet.

In der Region um Frankfurt am Main wird der frische, trübe, nicht pasteurisierte Apfelsaft „Süßer“ genannt und zur Erntezeit genossen.

Streuobstwiesen sind eine traditionelle Form des Apfelanbaus. Deutsche Fruchtsafthersteller setzen sich aus Naturschutz- und Qualitätsgründen für dessen Erhaltung und Förderung ein. In Deutschland wird der Apfel bei der Fruchtsaftherstellung zu 100 Prozent verarbeitet. Etwa 75 Prozent ist die Saftausbeute, 25 Prozent bleiben als ausgepresste Maische mit Schalen und Kernen übrig – das ist der so genannte Trester. Er geht etwa zur Hälfte in die Herstellung von Apfelpektin, das z. B. als pflanzliches Geliermittel verwendet werden kann. Die andere Hälfte geht in die Tierfütterung oder Energiegewinnung.
Apple juice is a fruit juice made by the maceration and pressing of apples. The resulting expelled juice may be further treated by enzymatic and centrifugal clarification to remove the starch and pectin, which holds fine particulate in suspension, and then pasteurized for packaging in glass, metal or aseptic processing system containers, or further treated by dehydration processes to a concentrate.

Russet apple juice from Bolney, Mid Sussex, England, in a glass.
Due to the complex and costly equipment required to extract and clarify juice from apples in large volume, apple juice is normally commercially produced. In the United States, unfiltered fresh apple juice is made by smaller operations in areas of high apple production, in the form of unclarified apple cider. Apple juice is one of the most common fruit juices in the world, with world production led by China, Poland, the United States, and Germany.

Vitamin C is sometimes added by fortification, because content is variable,[2] and much of that is lost in processing.[citation needed] Vitamin C also helps to prevent oxidation of the product.[3] Other vitamin concentrations are low, but apple juice does contain various mineral nutrients, including boron, which may promote healthy bones.[4] Apple juice has a significant concentration of natural phenols of low molecular weight (including chlorogenic acid, flavan-3-ols, and flavonols) and procyanidins[5] that may protect from diseases associated with aging due to the antioxidant effects which help reduce the likelihood of developing cancer and Alzheimer’s disease.[6] Research suggests that apple juice increases acetylcholine in the brain, possibly resulting in improved memory.[7] Despite having some health benefits, apple juice is high in sugar. It has 28 g carbohydrates (24 g sugars) per 230 g (8 ounces). This results in 130 calories per 230 g (8 ounces) – protein and fat are not significant. Also like most fruit juice, apple juice contains a similar amount of sugar as the raw fruit, but lacks the fiber content.
While apple juice generally refers to the filtered, pasteurised product of apple pressing, an unfiltered and sometimes unpasteurised product commonly known as apple cider in the United States and parts of Canada may be packaged and sold as apple juice. In the U.S., the opposite is often seen; filtered and clarified juice (including carbonated varieties) may be sold as "apple cider", thus there is an unclear distinction between filtered apple juice and natural apple cider.[8] In other places such as New Zealand, Australia and the United Kingdom, apple cider is an alcoholic beverage. The alcoholic beverage referred to as cider in these areas is usually referred to as hard cider in the United States.

Recycling is a process to change (waste) materials into new products to prevent waste of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air pollution (from incineration) and water pollution (from landfilling) by reducing the need for "conventional" waste disposal, and lower greenhouse gas emissions as compared to plastic production.[1][2] Recycling is a key component of modern waste reduction and is the third component of the "Reduce, Reuse and Recycle" waste hierarchy.

There are some ISO standards related to recycling such as ISO 15270:2008 for plastics waste and ISO 14001:2004 for environmental management control of recycling practice.

Recyclable materials include many kinds of glass, paper, metal, plastic, textiles, and electronics. Although similar in effect, the composting or other reuse of biodegradable waste—such as food or garden waste—is considered recycling.[2] Materials to be recycled are either brought to a collection center or picked up from the curbside, then sorted, cleaned, and reprocessed into new materials bound for manufacturing.

In the strictest sense, recycling of a material would produce a fresh supply of the same material—for example, used office paper would be converted into new office paper, or used foamed polystyrene into new polystyrene. However, this is often difficult or too expensive (compared with producing the same product from raw materials or other sources), so "recycling" of many products or materials involves their reuse in producing different materials (e.g., paperboard) instead. Another form of recycling is the salvage of certain materials from complex products, either due to their intrinsic value (e.g., lead from car batteries, or gold from computer components), or due to their hazardous nature (e.g., removal and reuse of mercury from various items). Critics dispute the net economic and environmental benefits of recycling over its costs, and suggest that proponents of recycling often make matters worse and suffer from confirmation bias. Specifically, critics argue that the costs and energy used in collection and transportation detract from (and outweigh) the costs and energy saved in the production process; also that the jobs produced by the recycling industry can be a poor trade for the jobs lost in logging, mining, and other industries associated with virgin production; and that materials such as paper pulp can only be recycled a few times before material degradation prevents further recycling. Proponents of recycling dispute each of these claims, and the validity of arguments from both sides has led to enduring controversy.
Recycling has been a common practice for most of human history, with recorded advocates as far back as Plato in 400 BC. During periods when resources were scarce, archaeological studies of ancient waste dumps show less household waste (such as ash, broken tools and pottery)—implying more waste was being recycled in the absence of new material.

In pre-industrial times, there is evidence of scrap bronze and other metals being collected in Europe and melted down for perpetual reuse.[4] In Britain dust and ash from wood and coal fires was collected by ‘dustmen’ and downcycled as a base material used in brick making. The main driver for these types of recycling was the economic advantage of obtaining recycled feedstock instead of acquiring virgin material, as well as a lack of public waste removal in ever more densely populated areas.[3] In 1813, Benjamin Law developed the process of turning rags into ‘shoddy’ and ‘mungo’ wool in Batley, Yorkshire. This material combined recycled fibres with virgin wool. The West Yorkshire shoddy industry in towns such as Batley and Dewsbury, lasted from the early 19th century to at least 1914.

Industrialization spurred demand for affordable materials; aside from rags, ferrous scrap metals were coveted as they were cheaper to acquire than was virgin ore. Railroads both purchased and sold scrap metal in the 19th century, and the growing steel and automobile industries purchased scrap in the early 20th century. Many secondary goods were collected, processed, and sold by peddlers who combed dumps, city streets, and went door to door looking for discarded machinery, pots, pans, and other sources of metal. By World War I, thousands of such peddlers roamed the streets of American cities, taking advantage of market forces to recycle post-consumer materials back into industrial production.[5]

Beverage bottles were recycled with a refundable deposit at some drink manufacturers in Great Britain and Ireland around 1800, notably Schweppes.[6] An official recycling system with refundable deposits was established in Sweden for bottles in 1884 and aluminium beverage cans in 1982, by law, leading to a recycling rate for beverage containers of 84–99 percent depending on type, and average use of a glass bottle is over 20 refills.

Wartime
Recycling was a highlight throughout World War II. During the war, financial constraints and significant material shortages due to war efforts made it necessary for countries to reuse goods and recycle materials.[7] It was these resource shortages caused by the world wars, and other such world-changing occurrences that greatly encouraged recycling.[8] The struggles of war claimed much of the material resources available, leaving little for the civilian population.[7] It became necessary for most homes to recycle their waste, as recycling offered an extra source of materials allowing people to make the most of what was available to them. Recycling materials that were used in the household, meant more resources were available to support war efforts. This in turn meant a better chance of victory at war.[7] Massive government promotion campaigns were carried out in World War II in every country involved in the war, urging citizens to donate metals and conserve fibre, as a matter of significant patriotic importance. There was patriotism in recycling.

Post-war
A considerable investment in recycling occurred in the 1970s, due to rising energy costs.[citation needed] Recycling aluminium uses only 5% of the energy required by virgin production; glass, paper and metals have less dramatic but very significant energy savings when recycled feedstock is used.

As of 2014, the European Union has about 50% of world share of the waste and recycling industries, with over 60,000 companies employing 500,000 persons, with a turnover of €24 billion.[10] Countries have to reach recycling rates of at least 50%, while the lead countries are around 65% and the EU average is 39% as of 2013.
For a recycling program to work, having a large, stable supply of recyclable material is crucial. Three legislative options have been used to create such a supply: mandatory recycling collection, container deposit legislation, and refuse bans. Mandatory collection laws set recycling targets for cities to aim for, usually in the form that a certain percentage of a material must be diverted from the city’s waste stream by a target date. The city is then responsible for working to meet this target.[2]

Container deposit legislation involves offering a refund for the return of certain containers, typically glass, plastic, and metal. When a product in such a container is purchased, a small surcharge is added to the price. This surcharge can be reclaimed by the consumer if the container is returned to a collection point. These programs have been very successful, often resulting in an 80 percent recycling rate. Despite such good results, the shift in collection costs from local government to industry and consumers has created strong opposition to the creation of such programs in some areas.[2]

A third method of increase supply of recyclates is to ban the disposal of certain materials as waste, often including used oil, old batteries, tires and garden waste. One aim of this method is to create a viable economy for proper disposal of banned products. Care must be taken that enough of these recycling services exist, or such bans simply lead to increased illegal dumping.[2]

Government-mandated demand
Legislation has also been used to increase and maintain a demand for recycled materials. Four methods of such legislation exist: minimum recycled content mandates, utilization rates, procurement policies, recycled product labeling.

Both minimum recycled content mandates and utilization rates increase demand directly by forcing manufacturers to include recycling in their operations. Content mandates specify that a certain percentage of a new product must consist of recycled material. Utilization rates are a more flexible option: industries are permitted to meet the recycling targets at any point of their operation or even contract recycling out in exchange for [trade]able credits. Opponents to both of these methods point to the large increase in reporting requirements they impose, and claim that they rob industry of necessary flexibility.

Governments have used their own purchasing power to increase recycling demand through what are called "procurement policies." These policies are either "set-asides," which earmark a certain amount of spending solely towards recycled products, or "price preference" programs which provide a larger budget when recycled items are purchased. Additional regulations can target specific cases: in the United States, for example, the Environmental Protection Agency mandates the purchase of oil, paper, tires and building insulation from recycled or re-refined sources whenever possible.[2]

The final government regulation towards increased demand is recycled product labeling. When producers are required to label their packaging with amount of recycled material in the product (including the packaging), consumers are better able to make educated choices. Consumers with sufficient buying power can then choose more environmentally conscious options, prompt producers to increase the amount of recycled material in their products, and indirectly increase demand. Standardized recycling labeling can also have a positive effect on supply of recyclates if the labeling includes information on how and where the product can be recycled.[2]

Recyclates
Recyclate is a raw material that is sent to, and processed in a waste recycling plant or materials recovery facility which will be used to form new products.[13] The material is collected in various methods and delivered to a facility where it undergoes re-manufacturing so that it can used in the production of new materials or products. For example, plastic bottles that are collected can be re-used and made into plastic pellets, a new product.[14]

Quality of recyclate
The quality of recyclates is recognized as one of the principal challenges that needs to be addressed for the success of a long term vision of a green economy and achieving zero waste. Recyclate quality is generally referring to how much of the raw material is made up of target material compared to the amount of non-target material and other non- recyclable material.[15] Only target material is likely to be recycled, so a higher amount of non-target and non-recyclable material will reduce the quantity of recycling product.[15] A high proportion of non-target and non-recyclable material can make it more difficult for re-processors to achieve ‘high-quality’ recycling. If the recyclate is of poor quality, it is more likely to end up being down-cycled or, in more extreme cases, sent to other recovery options or landfill.[15] For example, to facilitate the re-manufacturing of clear glass products there are tight restrictions for colored glass going into the re-melt process.

The quality of recyclate not only supports high quality recycling, it can deliver significant environmental benefits by reducing, reusing, and keeping products out of landfills.[15] High quality recycling can help support growth in the economy by maximizing the economic value of the waste material collected.[15] Higher income levels from the sale of quality recyclates can return value which can be significant to local governments, households and businesses.[15] Pursuing high quality recycling can also provide consumer and business confidence in the waste and resource management sector and may encourage investment in that sector.

There are many actions along the recycling supply chain that can influence and affect the material quality of recyclate.[16] It begins with the waste producers who place non-target and non-recyclable wastes in recycling collection. This can affect the quality of final recyclate streams or require further efforts to discard those materials at later stages in the recycling process.[16] The different collection systems can result in different levels of contamination. Depending on which materials are collected together, extra effort is required to sort this material back into separate streams and can significantly reduce the quality of the final product.[16] Transportation and the compaction of materials can make it more difficult to separate material back into separate waste streams. Sorting facilities are not one hundred per cent effective in separating materials, despite improvements in technology and quality recyclate which can see a loss in recyclate quality.[16] The storage of materials outside where the product can become wet can cause problems for re-processors. Reprocessing facilities may require further sorting steps to further reduce the amount of non-target and non-recyclable material.[16] Each action along the recycling path plays a part in the quality of recyclate.

Quality recyclate action plan (Scotland)
The Recyclate Quality Action Plan of Scotland sets out a number of proposed actions that the Scottish Government would like to take forward in order to drive up the quality of the materials being collected for recycling and sorted at materials recovery facilities before being exported or sold on to the reprocessing market.[16]

The plan’s objectives are to:

Drive up the quality of recyclate.
Deliver greater transparency around the quality of recyclate.
Provide help to those contracting with materials recycling facilities to identify what is required of them
Ensure compliance with the Waste (Scotland) regulations 2012.
Stimulate a household market for quality recyclate.
Address and reduce issues surrounding the Waste Shipment Regulations.
The plan focuses on three key areas, with fourteen actions which were identified to increase the quality of materials collected, sorted and presented to the processing market in Scotland.[17]

The three areas of focus are:

Collection systems and input contamination
Sorting facilities – material sampling and transparency
Material quality benchmarking and standards
Recycling consumer waste
A number of different systems have been implemented to collect recyclates from the general waste stream. These systems lie along the spectrum of trade-off between public convenience and government ease and expense. The three main categories of collection are "drop-off centres," "buy-back centres," and "curbside collection".

Drop-off centres
Drop-off centres require the waste producer to carry the recyclates to a central location, either an installed or mobile collection station or the reprocessing plant itself. They are the easiest type of collection to establish, but suffer from low and unpredictable throughput.

Buy-back centres
Buy-back centres differ in that the cleaned recyclates are purchased, thus providing a clear incentive for use and creating a stable supply. The post-processed material can then be sold on, hopefully creating a profit. Unfortunately, government subsidies are necessary to make buy-back centres a viable enterprise, as according to the United States’ National Waste & Recycling Association, it costs on average US$50 to process a ton of material, which can only be resold for US$30.[2]

Curbside collection
Main article: Curbside collection
Curbside collection encompasses many subtly different systems, which differ mostly on where in the process the recyclates are sorted and cleaned. The main categories are mixed waste collection, commingled recyclables and source separation.[2] A waste collection vehicle generally picks up the waste.
At one end of the spectrum is mixed waste collection, in which all recyclates are collected mixed in with the rest of the waste, and the desired material is then sorted out and cleaned at a central sorting facility. This results in a large amount of recyclable waste, paper especially, being too soiled to reprocess, but has advantages as well: the city need not pay for a separate collection of recyclates and no public education is needed. Any changes to which materials are recyclable is easy to accommodate as all sorting happens in a central location.[2]

In a commingled or single-stream system, all recyclables for collection are mixed but kept separate from other waste. This greatly reduces the need for post-collection cleaning but does require public education on what materials are recyclable.[2][4]

Source separation is the other extreme, where each material is cleaned and sorted prior to collection. This method requires the least post-collection sorting and produces the purest recyclates, but incurs additional operating costs for collection of each separate material. An extensive public education program is also required, which must be successful if recyclate contamination is to be avoided.[2]

Source separation used to be the preferred method due to the high sorting costs incurred by commingled (mixed waste) collection. Advances in sorting technology (see sorting below), however, have lowered this overhead substantially—many areas which had developed source separation programs have since switched to comingled collection.[4]

Distributed Recycling
For some waste materials such as plastic, recent technical devices called recyclebots[18] enable a form of distributed recycling. Preliminary life-cycle analysis(LCA) indicates that such distributed recycling of HDPE to make filament of 3-D printers in rural regions is energetically favorable to either using virgin resin or conventional recycling processes because of reductions in transportation energy[19]

Sorting

Once commingled recyclates are collected and delivered to a central collection facility, the different types of materials must be sorted. This is done in a series of stages, many of which involve automated processes such that a truckload of material can be fully sorted in less than an hour.[4] Some plants can now sort the materials automatically, known as single-stream recycling. In plants a variety of materials are sorted such as paper, different types of plastics, glass, metals, food scraps, and most types of batteries.[20] A 30 percent increase in recycling rates has been seen in the areas where these plants exist.[21]

Initially, the commingled recyclates are removed from the collection vehicle and placed on a conveyor belt spread out in a single layer. Large pieces of corrugated fiberboard and plastic bags are removed by hand at this stage, as they can cause later machinery to jam.

Next, automated machinery separates the recyclates by weight, splitting lighter paper and plastic from heavier glass and metal. Cardboard is removed from the mixed paper, and the most common types of plastic, PET (#1) and HDPE (#2), are collected. This separation is usually done by hand, but has become automated in some sorting centers: a spectroscopic scanner is used to differentiate between different types of paper and plastic based on the absorbed wavelengths, and subsequently divert each material into the proper collection channel.[4]

Strong magnets are used to separate out ferrous metals, such as iron, steel, and tin-plated steel cans ("tin cans"). Nonferrous metals are ejected by magnetic eddy currents in which a rotating magnetic field induces an electric current around the aluminium cans, which in turn creates a magnetic eddy current inside the cans. This magnetic eddy current is repulsed by a large magnetic field, and the cans are ejected from the rest of the recyclate stream.[4]

Finally, glass must be sorted by hand on the basis of its color: brown, amber, green, or clear.[4]

This process of recycling as well as reusing the recycled material proves to be advantageous for many reasons as it reduces amount of waste sent to landfills, conserves natural resources, saves energy, reduces greenhouse gas emissions, and helps create new jobs. Recycled materials can also be converted into new products that can be consumed again such as paper, plastic, and glass.[22]

The City and County of San Francisco’s Department of the Environment offers one of the best recycling programs to support its city-wide goal of Zero Waste by 2020.[23] San Francisco’s refuse hauler, Recology, operates an effective recyclables sorting facility in San Francisco, which helped San Francisco reach a record-breaking diversion rate of 80%.[24]

Recycling industrial waste

Although many government programs are concentrated on recycling at home, a large portion of waste is generated by industry. The focus of many recycling programs done by industry is the cost-effectiveness of recycling. The ubiquitous nature of cardboard packaging makes cardboard a commonly recycled waste product by companies that deal heavily in packaged goods, like retail stores, warehouses, and distributors of goods. Other industries deal in niche or specialized products, depending on the nature of the waste materials that are present.

The glass, lumber, wood pulp, and paper manufacturers all deal directly in commonly recycled materials. However, old rubber tires may be collected and recycled by independent tire dealers for a profit.

Levels of metals recycling are generally low. In 2010, the International Resource Panel, hosted by the United Nations Environment Programme (UNEP) published reports on metal stocks that exist within society[25] and their recycling rates.[26] The Panel reported that the increase in the use of metals during the 20th and into the 21st century has led to a substantial shift in metal stocks from below ground to use in applications within society above ground. For example, the in-use stock of copper in the USA grew from 73 to 238 kg per capita between 1932 and 1999.

The report authors observed that, as metals are inherently recyclable, the metals stocks in society can serve as huge mines above ground (the term "urban mining" has been coined with this idea in mind[27]). However, they found that the recycling rates of many metals are very low. The report warned that the recycling rates of some rare metals used in applications such as mobile phones, battery packs for hybrid cars and fuel cells, are so low that unless future end-of-life recycling rates are dramatically stepped up these critical metals will become unavailable for use in modern technology.

The military recycles some metals. The U.S. Navy’s Ship Disposal Program uses ship breaking to reclaim the steel of old vessels. Ships may also be sunk to create an artificial reef. Uranium is a very dense metal that has qualities superior to lead and titanium for many military and industrial uses. The uranium left over from processing it into nuclear weapons and fuel for nuclear reactors is called depleted uranium, and it is used by all branches of the U.S. military use for armour-piercing shells and shielding.

The construction industry may recycle concrete and old road surface pavement, selling their waste materials for profit.

Some industries, like the renewable energy industry and solar photovoltaic technology in particular, are being proactive in setting up recycling policies even before there is considerable volume to their waste streams, anticipating future demand during their rapid growth.[28]

Recycling of plastics is more difficult, as most programs can’t reach the necessary level of quality. Recycling of PVC often results in downcycling of the material, which means only products of lower quality standard can be made with the recycled material. A new approach which allows an equal level of quality is the Vinyloop process. It was used after the London Olympics 2012 to fulfill the PVC Policy.[29]

e-Waste recycling
Main article: Computer recycling
E-waste is a growing problem, accounting for 20-50 million metric tons of global waste per year according to the EPA. Many recyclers do not recycle e-waste or do not do so responsibly. The e-Stewards certification was created to ensure recyclers are held to the highest standards for environmental responsibility and to give consumers an easy way to identify responsible recyclers. e-Cycle, LLC, was the first mobile recycling company to be e-Stewards certified.

Plastic recycling
Main article: Plastic recycling
Plastic recycling is the process of recovering scrap or waste plastic and reprocessing the material into useful products, sometimes completely different in form from their original state. For instance, this could mean melting down soft drink bottles and then casting them as plastic chairs and tables.[30]

Physical Recycling
Some plastics are remelted to form new plastic objects, for example PET water bottles can be converted into clothing grade polyester. A disadvantage of this type of recycling is that in each use and recycling cycle the molecular weight of the polymer can change further and the levels of unwanted substances in the plastic can increase.

Chemical Recycling
For some polymers it is possible to convert them back into monomers, for example PET can be treated with an alcohol and a catalyst to form a dialkyl terephthalate. The terephthalate diester can be used with ethylene glycol to form a new polyester polymer. Thus it is possible to make the pure polymer again.

Waste Plastic Pyrolysis to fuel oil
Another process involves the conversion of assorted polymers into petroleum by a much less precise thermal depolymerization process. Such a process would be able to accept almost any polymer or mix of polymers, including thermoset materials such as vulcanized rubber tires and the biopolymers in feathers and other agricultural waste. Like natural petroleum, the chemicals produced can be made into fuels as well as polymers. RESEM Technology[31] plant of this type exists in Carthage, Missouri, USA, using turkey waste as input material. Gasification is a similar process, but is not technically recycling since polymers are not likely to become the result. Plastic Pyrolysis can convert petroleum based waste streams such as plastics into quality fuels, carbons. Given below is the list of suitable plastic raw materials for pyrolysis:

Mixed plastic (HDPE, LDPE, PE, PP, Nylon, Teflon, PS, ABS, FRP etc.)
Mixed waste plastic from waste paper mill
Multi Layered Plastic
Recycling codes
Main article: Recycling codes
In order to meet recyclers’ needs while providing manufacturers a consistent, uniform system, a coding system is developed. The recycling code for plastics was introduced in 1988 by plastics industry through the Society of the Plastics Industry, Inc.[32] Because municipal recycling programs traditionally have targeted packaging—primarily bottles and containers—the resin coding system offered a means of identifying the resin content of bottles and containers commonly found in the residential waste stream.

Plastic products are printed with numbers 1–7 depending on the type of resin. Type 1 plastic, PET (or PETE): polyethylene terephthalate, is commonly found in soft drink and water bottles. Type 2, HDPE: high-density polyethylene is found in most hard plastics such as milk jugs, laundry detergent bottles, and some dishware. Type 3, PVC or V (vinyl), includes items like shampoo bottles, shower curtains, hoola hoops, credit cards, wire jacketing, medical equipment, siding, and piping. Type 4, called LDPE, or low-density polyethylene, is found in shopping bags, squeezable bottles, tote bags, clothing, furniture, and carpet. Type 5 is PP which stands for polypropylene and makes up syrup bottles, straws, Tupperware, and some automotive parts. Type 6 is PS: polystyrene and makes up meat trays, egg cartons, clamshell containers and compact disc cases. Type 7 includes all other plastics like bulletproof materials, 3- and 5-gallon water bottles, and sunglasses.[34] Types 1 and 2 are the most commonly recycled.

There is some debate over whether recycling is economically efficient. It is said[by whom?] that dumping 10,000 tons of waste in a landfill creates six jobs, while recycling 10,000 tons of waste can create over 36 jobs. However, the cost effectiveness of creating the additional jobs remains unproven. According to the U.S. Recycling Economic Informational Study, there are over 50,000 recycling establishments that have created over a million jobs in the US.[37] Two years after New York City declared that implementing recycling programs would be "a drain on the city," New York City leaders realized that an efficient recycling system could save the city over $20 million.[38] Municipalities often see fiscal benefits from implementing recycling programs, largely due to the reduced landfill costs.[39] A study conducted by the Technical University of Denmark according to the Economist found that in 83 percent of cases, recycling is the most efficient method to dispose of household waste.[4][9] However, a 2004 assessment by the Danish Environmental Assessment Institute concluded that incineration was the most effective method for disposing of drink containers, even aluminium ones.[40]

Fiscal efficiency is separate from economic efficiency. Economic analysis of recycling do not include what economists call externalities, which are unpriced costs and benefits that accrue to individuals outside of private transactions. Examples include: decreased air pollution and greenhouse gases from incineration, reduced hazardous waste leaching from landfills, reduced energy consumption, and reduced waste and resource consumption, which leads to a reduction in environmentally damaging mining and timber activity. About 4,000 minerals are known, of these only a few hundred minerals in the world are relatively common.[41] Known reserves of phosphorus will be exhausted within the next 100 years at current rates of usage.[42][43] Without mechanisms such as taxes or subsidies to internalize externalities, businesses will ignore them despite the costs imposed on society.[opinion] To make such nonfiscal benefits economically relevant, advocates have pushed for legislative action to increase the demand for recycled materials.[2] The United States Environmental Protection Agency (EPA) has concluded in favor of recycling, saying that recycling efforts reduced the country’s carbon emissions by a net 49 million metric tonnes in 2005.[4] In the United Kingdom, the Waste and Resources Action Programme stated that Great Britain’s recycling efforts reduce CO2 emissions by 10–15 million tonnes a year.[4] Recycling is more efficient in densely populated areas, as there are economies of scale involved.

Certain requirements must be met for recycling to be economically feasible and environmentally effective. These include an adequate source of recyclates, a system to extract those recyclates from the waste stream, a nearby factory capable of reprocessing the recyclates, and a potential demand for the recycled products. These last two requirements are often overlooked—without both an industrial market for production using the collected materials and a consumer market for the manufactured goods, recycling is incomplete and in fact only "collection".[2]

Many[who?] economists favor a moderate level of government intervention to provide recycling services. Economists of this mindset probably view product disposal as an externality of production and subsequently argue government is most capable of alleviating such a dilemma.

Trade in recyclates
Certain countries trade in unprocessed recyclates. Some have complained that the ultimate fate of recyclates sold to another country is unknown and they may end up in landfills instead of reprocessed. According to one report, in America, 50–80 percent of computers destined for recycling are actually not recycled.[44][45] There are reports of illegal-waste imports to China being dismantled and recycled solely for monetary gain, without consideration for workers’ health or environmental damage. Although the Chinese government has banned these practices, it has not been able to eradicate them.[46] In 2008, the prices of recyclable waste plummeted before rebounding in 2009. Cardboard averaged about £53/tonne from 2004–2008, dropped to £19/tonne, and then went up to £59/tonne in May 2009. PET plastic averaged about £156/tonne, dropped to £75/tonne and then moved up to £195/tonne in May 2009.[47] Certain regions have difficulty using or exporting as much of a material as they recycle. This problem is most prevalent with glass: both Britain and the U.S. import large quantities of wine bottled in green glass. Though much of this glass is sent to be recycled, outside the American Midwest there is not enough wine production to use all of the reprocessed material. The extra must be downcycled into building materials or re-inserted into the regular waste stream.[2][4]

Similarly, the northwestern United States has difficulty finding markets for recycled newspaper, given the large number of pulp mills in the region as well as the proximity to Asian markets. In other areas of the U.S., however, demand for used newsprint has seen wide fluctuation.[2]

In some U.S. states, a program called RecycleBank pays people to recycle, receiving money from local municipalities for the reduction in landfill space which must be purchased. It uses a single stream process in which all material is automatically sorted.

Much of the difficulty inherent in recycling comes from the fact that most products are not designed with recycling in mind. The concept of sustainable design aims to solve this problem, and was laid out in the book "Cradle to Cradle: Remaking the Way We Make Things" by architect William McDonough and chemist Michael Braungart. They suggest that every product (and all packaging they require) should have a complete "closed-loop" cycle mapped out for each component—a way in which every component will either return to the natural ecosystem through biodegradation or be recycled indefinitely.[4] While recycling diverts waste from entering directly into landfill sites, current recycling misses the dissipative components. Complete recycling is impracticable as highly dispersed wastes become so diluted that the energy needed for their recovery becomes increasingly excessive. "For example, how will it ever be possible to recycle the numerous chlorinated organic hydrocarbons that have bioaccumulated in animal and human tissues across the globe, the copper dispersed in fungicides, the lead in widely applied paints, or the zinc oxides present in the finely dispersed rubber powder that is abraded from automobile tires?"[50]:260 As with environmental economics, care must be taken to ensure a complete view of the costs and benefits involved. For example, paperboard packaging for food products is more easily recycled than most plastic, but is heavier to ship and may result in more waste from spoilage.[51]

Energy and material flows
The amount of energy saved through recycling depends upon the material being recycled and the type of energy accounting that is used. Emergy (spelled with an m) analysis, for example, budgets for the amount of energy of one kind (exergy) that is required to make or transform things into another kind of product or service. Using emergy life-cycle analysis researchers have concluded that materials with large refining costs have the greatest potential for high recycle benefits. Moreover, the highest emergy efficiency accrues from systems geared toward material recycling, where materials are engineered to recycle back into their original form and purpose, followed by adaptive reuse systems where the materials are recycled into a different kind of product, and then by-product reuse systems where parts of the products are used to make an entirely different product.[52]

The Energy Information Administration (EIA) states on its website that "a paper mill uses 40 percent less energy to make paper from recycled paper than it does to make paper from fresh lumber."[53] Some critics argue that it takes more energy to produce recycled products than it does to dispose of them in traditional landfill methods, since the curbside collection of recyclables often requires a second waste truck. However, recycling proponents point out that a second timber or logging truck is eliminated when paper is collected for recycling, so the net energy consumption is the same. An Emergy life-cycle analysis on recycling revealed that fly ash, aluminum, recycled concrete aggregate, recycled plastic, and steel yield higher efficiency ratios, whereas the recycling of lumber generates the lowest recycle benefit ratio. Hence, the specific nature of the recycling process, the methods used to analyse the process, and the products involved affect the energy savings budgets.[52]

It is difficult to determine the amount of energy consumed or produced in waste disposal processes in broader ecological terms, where causal relations dissipate into complex networks of material and energy flow. For example, "cities do not follow all the strategies of ecosystem development. Biogeochemical paths become fairly straight relative to wild ecosystems, with very reduced recycling, resulting in large flows of waste and low total energy efficiencies. By contrast, in wild ecosystems, one population’s wastes are another population’s resources, and succession results in efficient exploitation of available resources. However, even modernized cities may still be in the earliest stages of a succession that may take centuries or millennia to complete."[54]:720 How much energy is used in recycling also depends on the type of material being recycled and the process used to do so. Aluminium is generally agreed to use far less energy when recycled rather than being produced from scratch. The EPA states that "recycling aluminum cans, for example, saves 95 percent of the energy required to make the same amount of aluminum from its virgin source, bauxite."[55][56] In 2009 more than half of all aluminium cans produced came from recycled aluminium.

Economist Steven Landsburg has suggested that the sole benefit of reducing landfill space is trumped by the energy needed and resulting pollution from the recycling process.[59] Others, however, have calculated through life cycle assessment that producing recycled paper uses less energy and water than harvesting, pulping, processing, and transporting virgin trees.[60] When less recycled paper is used, additional energy is needed to create and maintain farmed forests until these forests are as self-sustainable as virgin forests.

Other studies have shown that recycling in itself is inefficient to perform the “decoupling” of economic development from the depletion of non-renewable raw materials that is necessary for sustainable development.[61] The international transportation or recycle material flows through "…different trade networks of the three countries result in different flows, decay rates, and potential recycling returns."[62]:1 As global consumption of a natural resources grows, its depletion is inevitable. The best recycling can do is to delay, complete closure of material loops to achieve 100 percent recycling of nonrenewables is impossible as micro-trace materials dissipate into the environment causing severe damage to the planet’s ecosystems.[63][64][65] Historically, this was identified as the metabolic rift by Karl Marx, who identified the unequal exchange rate between energy and nutrients flowing from rural areas to feed urban cities that create effluent wastes degrading the planet’s ecological capital, such as loss in soil nutrient production.[66][67] Energy conservation also leads to what is known as Jevon’s paradox, where improvements in energy efficiency lowers the cost of production and leads to a rebound effect where rates of consumption and economic growth increases.

The amount of money actually saved through recycling depends on the efficiency of the recycling program used to do it. The Institute for Local Self-Reliance argues that the cost of recycling depends on various factors around a community that recycles, such as landfill fees and the amount of disposal that the community recycles. It states that communities start to save money when they treat recycling as a replacement for their traditional waste system rather than an add-on to it and by "redesigning their collection schedules and/or trucks."[69]

In some cases, the cost of recyclable materials also exceeds the cost of raw materials. Virgin plastic resin costs 40 percent less than recycled resin.[70] Additionally, a United States Environmental Protection Agency (EPA) study that tracked the price of clear glass from July 15 to August 2, 1991, found that the average cost per ton ranged from $40 to $60,[71] while a USGS report shows that the cost per ton of raw silica sand from years 1993 to 1997 fell between $17.33 and $18.10.[72]

In a 1996 article for The New York Times, John Tierney argued that it costs more money to recycle the trash of New York City than it does to dispose of it in a landfill. Tierney argued that the recycling process employs people to do the additional waste disposal, sorting, inspecting, and many fees are often charged because the processing costs used to make the end product are often more than the profit from its sale.[73] Tierney also referenced a study conducted by the Solid Waste Association of North America (SWANA) that found in the six communities involved in the study, "all but one of the curbside recycling programs, and all the composting operations and waste-to-energy incinerators, increased the cost of waste disposal."[74]

Tierney also points out that "the prices paid f

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What are the factors that determine vehicle shipping quotes?

What are the factors that determine vehicle shipping quotes?

There are many factors that determine vehicle shipping quotes. Those of you who are looking for vehicle shipping services, you must know these factors as it would help you save money on the same.

The major factor that determines the auto shipping quote is the total distance that needs to be covered. If a car is moving from New York to Florida, the vehicle shipping cost would be less compared to the cost of moving the car from New York to Canada. Long distances add to the fuel expenses, freight charges, and toll tax being borne by the vehicle shipping company for shipping your car and therefore they charge you more.

The second factor that decides the rate of vehicle shipping is the make and model of the car. The rate for shipping a normal car, motorcycle, van or SUV is far less than what is charged for moving an antique or vintage car. Vintage car and antique cars need special care and hence the rate is more.

The condition of the vehicle is the third factor that determines its shipping quote. If the vehicle is not in working condition and it needs to be pushed on to the vehicle carrier, the vehicle shipping quote would be more. But if the car is in good condition and it can be easily driven onto the carrier, the vehicle shipping company would charge you less for that.

The size and weight of the vehicles also decide their vehicle shipping quotes. A large sized vehicle that is bulky in weight would cost more than a small, compact vehicle. This is because large vehicles take more space, leaving little scope for other vehicles to come onto the carrier. The auto shipping companies therefore charge more for shipping such vehicles.

Lastly, the value of the vehicles also plays a crucial role in deciding their shipping quotes. Expensive vehicles need added insurance coverage for their safety and security and therefore the vehicle shipping quotes is more for them compared to normal and affordable vehicles. 

When you are comparing vehicle shipping quotes, keep all these factors in mind. The providers of vehicle shipping services would ask you to refurbish them all such details regarding the make and model of your car, the condition of your car, its value, the pick up and drop off city, date, and time when you want to avail the vehicle shipping services, and so on and so forth. If you want to save money on vehicle shipping quotes, get quotes from several companies and compare them thoroughly. By shopping around and comparing, you can save a lot on vehicle shipping.

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