Ret ind efter Mælkevejen
Ugens billede viser kraftige laserstråler, som udsendes fra Unit Telescope 4, eller "Yepun" ved ESOs Very Large Telescope (VLT) i Chiles Atacamaørken. De kommer fra VLTs 4 Laser Guide Star Facility, som gør det muligt for astronomerne at optage meget skarpe billeder af rummet, ved hjælp af en teknologi, som kaldes adaptiv optik.
Med adaptiv optik kan teleskoperne korrigere for den turbulens, som atmosfæren skaber, og som er det, der forårsager tindren og uskarphed for stjerner og andre himmelobjekter, når man observerer dem. Man får deformerbare spejle til at ændre facon op til 1000 gange i sekundet, i det feed-backkredsløb med den turbulens, som observeres. Astronomerne måler turbulensen ved at holde øje med en klar stjerne tæt ved det område, som man vil observere. Hvis der ikke er en passende stjerne i nærheden, skaber de selv kunstige stjerner i Jordens atmosfære ved hjælp af laserne. De har en speciel orangegul farve (med en bølgelængde på 589 nm), som påvirker natriumatomer i den øvre atmosfære, omkring 90 km oppe, så de lyser op som en stjerne.
I baggrunden ser man Mælkevejens kendte lysbånd, som næsten ser ud til at pege i samme retning som laserstrålerne. Desuden kan man se et svagt grønt skær ud over himlen. Det er naturfænomenet airglow, som er lys, som naturligt udsendes af atomer og molekyler i atmosfæren. Man kan kun se airglow fra steder, hvor himlen er mørk nok til, at det ikke overstråles af den menneskeskabte lysforurening.
Kilde:ESO/A. Ghizzi Panizza (www.albertoghizzipanizza.com)
Om billedet
| Id: | potw2222a |
| Sprog: | da |
| Type: | Foto |
| Udgivelsesdato: | 30. maj 2022 06:00 |
| Størrelse: | 6048 x 4024 px |
Om objektet
| Navn: | Laser Guide Star, VLT Unit Telescopes |
| Type: | Unspecified : Technology : Observatory : Telescope |
Billedformater
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