VLTs SPHERE lurer på lumske klippeklumper
Billederne her viser fire af de mange millioner klippestykker, som befinder sig i asteroidebæltet, i området imellem Mars og Jupiter, hvor grænsen går imellem de indre klippeplaneter og de ydre gasplaneter i vores Solsystem. Optagelserne er fra instrumentet SPHERE (Spectro-Polarimetric High-contrast Exoplanet REsearch), som er monteret på ESOs Very Large Telescope (VLT) på Paranalobservatoriet i Chile.
Fra øverst til venstre og med uret rundt er det 29 Amphitrite, 324 Bamberga, 2 Pallas, og 89 Julia. 2 Pallas er godt 510 kilometer i diameter og opkaldt efter den græske gudinde Pallas Athena. Det er den tredjestørste asteroide i det indre asteroidebælte, og det er en af de største asteroider i hele Solsystemet. I alt indeholder Pallas omkring 7% af alt det stof, der er i hele asteroidebæltet, og det er nok til, at den en gang faktisk blev klassificeret som en planet. 89 Julia er en tredjedel så stor som 2 Pallas. Det formodes, at den har fået navn efter helgeninden St Julia oaf Corsica. Dens klippesammensætning gør, at den er klassificeret som en S-type asteroide. Det samme er 29 Amphitrite, som blev opdaget i 1854. 324 Bamberga er en af de største C-type asteroider i det indre asteroidebælte, og den blev opdaget så sent som i 1892 af Johann Palisa. Idag menes det, at C-type asteroider oprindeligt er himmellegemer fra det ydre af Solsystemet, som er kommet tættere på Solen i samme omgang, som de store gasplaneter er vandrest udad. Derfor menes det, at de indeholder is i deres indre.
Selvom asteroidebæltet ofte bliver afbildet og beskrevet i science fiction som et område, hvor der sker masser af voldsomme kollisioner, og hvor der er tætpakket med store klippestykker, som heltemodige rumpiloter kun med nød og næppe når i sidste øjeblik at manøvrere udenom, så er der i virkeligheden ret så tomt. I hele asteroidebæltet er der i alt masser, som tilsammen svarer til 4% af Månens masse, og omkring halvdelen af massen er samlet i de fire største asteroider: Ceres, 4 Vesta, 2 Pallas, og 10 Hygiea.
Kilde:ESO/Vernazza et al.
Om billedet
| Id: | potw1749a |
| Sprog: | da |
| Type: | Planetarisk |
| Udgivelsesdato: | 4. december 2017 06:00 |
| Størrelse: | 1075 x 1075 px |
Om objektet
| Navn: | 29 Amphitrite, 2 Pallas, 324 Bamberga, 89 Julia |
| Type: | Solar System : Interplanetary Body : Asteroid |
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