Ein Laserleitstern streift das Firmament
Dieses atemberaubende Foto von Julien Girard zeigt einen hellen Laserstrahl, der zum Very Large Telescope (VLT) der ESO gehört, vor dem Nachthimmel über der chilenischen Atacama-Wüste. Weil der Laser während der 30-minütigen Belichtungszeit zum Ausgleich der Erddrehung bewegt wurde, erscheint der Strahl aufgefächert. Die Kamera, die das Bild aufgenommen hat, stand dagegen still, so dass die Sterne als Strichspuren abgebildet wurden, die besonders deutlich die unterschiedlichen Farben der Sterne zeigen.
Der Laser wird verwendet, um Natriumatome in 90 Kilometern Höhe zum Leuchten anzuregen und so in der Hochatmosphäre einen hellen Lichtpunkt – einen künstlichen Stern – zu erzeugen. Dieser sogenannte Laserleitstern wird dann als Referenz verwendet, um die Bildverschlechterungen durch die Einflüsse der Atmosphäre zu korrigieren. Dazu wird die Technik der sogenannten adaptiven Optik verwendet. Zwar können auch ausreichend helle echte Sterne als Referenz genommen werden, aber der Laserleitstern kann an jede gewünschte Stelle positioniert werden. Mit seiner Hilfe kann die adaptive Optik in viel mehr Himmelsbereichen eingesetzt werden.
Die vier großen Schutzbauten der 8,2-Meter-Hauptteleskope des VLT und dahinter das kleinere VLT Survey Telescope (VST) sind ebenfalls im Bild zu sehen. Julien arbeitet als Astronom für die ESO am VLT in Chile. In der Nacht, in der das hier gezeigte Foto aufgenommen wurde, unterstützte er Beobachtungen an dem VLT-Hauptteleskop auf der rechten Seite. Er nutzte die Gelegenheit, um seine Kamera aufzubauen, bevor er in den Kontrollraum zurückging und die VLT-Beobachtungen durchzuführen.
Die Bewegungen der Schutzbauten während der langen Belichtungszeit führen zu einem verwaschenen Eindruck. Ebenso sind schwache Lichtspuren zu erkennen, die von Personen stammen, die sich während der Belichtungszeit auf der Plattform zwischen den Teleskopen hin und her bewegt haben.
Julien hat dieses Foto in der „Your ESO Pictures“-Flickrgruppe veröffentlicht. Die besten Fotos aus dieser Gruppe werden regelmäßig für das Bild der Woche oder für unsere Bildergalerie ausgewählt. Als Teil des 50-jährigen Jubiläums der ESO freuen wir uns im Jahr 2012 besonders über historische Bilder mit Bezug zur ESO.
Links
- Dieses Bild mit Anmerkungen auf Julien Girards Flickr-Photostream
- Julien Girards Flickr-Photostream
- Die “Your ESO Pictures”-Flickrgruppe
- Ankündigung der "Your ESO Pictures"-Flickr-Gruppe
ESO/J. Girard (djulik.com)
Über das Bild
| ID: | potw1234a |
| Sprache: | de-ch |
| Typ: | Fotografisch |
| Veröffentlichungsdatum: | 20. August 2012 10:00 |
| Größe: | 4316 x 2876 px |
Über das Objekt
| Name: | Very Large Telescope |
| Typ: | Unspecified : Technology : Observatory : Facility |
Bildformate
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