Das VLT verfolgt Rosettas Komet
Der helle, neblige Fleck im Zentrum dieses Bildes ist der Komet 67P/Churyumov-Gerasimenko, oder kurz 67P/C-G. Dies ist nicht nur irgendein Komet: Er ist das Ziel für die Raumsonde Rosetta der ESA, die sich gegenwärtig tief innerhalb der Koma des Kometen und weniger als 100 km von seinem Kern befindet [1]. Weil Rosetta so nahe am Kometen ist, bietet die Beobachtung vom Boden die einzige Möglichkeit, die Gesamtheit von 67 P/C-G zu beobachten.
Dieses Bild wurde am 11. August 2014 mit einem der 8-Meter-Teleskope des Very Large Telescope (VLT) der ESO in Chile aufgenommen. 40 Einzelbelichtungen, von denen jede 50 Sekunden lang dauerte, wurden dazu überlagert und die Hintergrundsterne wurden entfernt, um die optimale Sicht auf den Kometen zu erreichen. Rosetta selbst ist innerhalb des zentralen Pixels dieses Bildes enthalten und ist viel zu klein, um aufgelöst zu werden.
Das VLT setzt sich aus vier Hauptteleskopen zusammen, die zusammenarbeiten können oder mit denen man einzeln den Nachthimmel studieren kann. Diese Beobachtungen nutzten das FORS2-Instrument (FOcal Reducer and low dispersion Spectrograph 2) an Hauptteleskop 1, das den Namen Antu trägt, der Ausdruck der eingeborenen Mapuche für die Sonne.
FORS2 kann in verschiedener Weise genutzt werden, für die Rosetta-Kampagne verwenden es die Astronomen, um den Kometen abzubilden und seine Helligkeit, Größe und Form zu bestimmen und auch um die Zusammensetzung der Koma zu analysieren.
Obwohl 67P/C-G in diesem Bild schwach erscheint, ist er klar erkennbar aktiv, und die staubige Koma erstreckt sich ungefähr 19.000 Kilometer vom Kern weg. Durch das Wegwehen des Staubes von der Sonne weg wird die Koma – die sich unterhalb der unteren rechten Ecke des Bildes befindet – asymmetrisch und beginnt einen charakteristischen Kometenschweif auszubilden.
Dies VLT-Bild ist Teil einer laufenden Zusammenarbeit von ESA und ESO 67P/C-G vom Boden zu beobachten, während Rosetta Messungen am Kometen vornimmt. Durchschnittlich jede zweite Nacht nimmt das VLT Bilder von dem Kometen auf. Diese Kurzzeitbelichtungen werden verwendet, um die Aktivität des Kometen aufzuzeichnen und zu studieren, wie seine Helligkeit sich verändert. Die Ergebnisse werden an das Rosetta-Projektteam übermittelt und liefern einen Teil der Informationen, die für die Planung der Flugbahn der Sonde um den Kometen benötigt werden.
Bemerkungen
[1] Rosetta erreichte am 6. August 2014 eine Entfernung von 100 km vom Kern des Kometen 67P/C-G und hat sich seitdem an ihn angenähert.
Bildnachweis:Colin Snodgrass/ESO/ESA
Über das Bild
| ID: | potw1436a |
| Sprache: | de-ch |
| Typ: | Beobachtung |
| Veröffentlichungsdatum: | 8. September 2014 10:00 |
| Größe: | 954 x 614 px |
Über das Objekt
| Name: | 67P/Churyumov-Gerasimenko |
| Typ: | Solar System : Interplanetary Body : Comet |
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