Krusninger og skaller
I sammenligning med de mere indviklede kolleger, spiralgalakserne ligner de elliptiske galakser mere slørede skyer. Den type galakser har bløde udefinerede grænser og klare kerneområder omgivet at et tåget diffust skær. Det første indtryk kan dog godt snyde. Mindst 10% af de elliptiske galakser strækker sig meget længere ud i verdensrummet end man kunne forvente, og de har en lang række fine detaljer, som man skal se godt efter for at opdage - det er for eksempel løkker og skaller.
Omkring 100 millioner lysår borte, i stjernebilledet Fiskene (Pisces) finder vi galaksen øverst til venstre i billedet her. Den hedder NGC 474. Det er et klart eksempel på en elliptisk galakse med skaller; enorme slørede haler snor sig omkring hovedområdet for galaksen, og den indre struktur udgøres af en serie koncentriske ringe. Faktisk kan vi slet ikke have hele galaksen indenfor billedfeltet her. De tynde ydre arme snor sig ud i rummet som røgstriber meget længere end NGC474s klartlysende centralområder.
Astronomerne er ikke sikre på, hvorfor nogle galakser ser sådan ud, men tanker er, at det har at gøre med tyngdekræfter - nemlig vekselvirkninger imellem nære galakser, hvis tyngdefelter vekselvirker. Det er muligt, at spiralgalaksen nede til højre, NGC 470 har trukket i dens større nabo i milliarder af år, så tæthedsbølger har påvirket strukturen i NGC 474.
Galakserne er observeret som en del af ESOs Cosmic Gemsprogram. Det er et formidlingsprogram, som har til formål at skabe billeder som er interessante, spændende eller blot smukke med ESOs teleskoper for brug i uddannelse og formidling overfor offentligheden. I programmen bruges tid ved teleskoperne, som ikke kan bruges til videnskabelige formål. Alt, hvad der indsamles af data kan måske også bruges videnskabeligt, og derfor er det tilgængeligt for astronomerne via ESOs videnskabsarkiv.
Kilde:ESO
Om billedet
| Id: | potw2001a |
| Sprog: | da |
| Type: | Observation |
| Udgivelsesdato: | 6. januar 2020 06:00 |
| Størrelse: | 1726 x 1744 px |
Om objektet
| Navn: | NGC 470, NGC 474 |
| Type: | Local Universe : Galaxy : Type : Spiral |
| Afstand: | 100 million lysår |
| Constellation: | Pisces |
Baggrundsbilleder
Koordinater
| Position (RA): | 1 19 55.68 |
| Position (Dec): | 3° 24' 34.10" |
| Field of view: | 7.32 x 7.24 arcminutes |
| Orientering: | Nord er 45.1° venstre fra lodret |
Farver & filtre
| Bånd | Bølgelængde | Teleskop |
|---|---|---|
| Optisk b | 440 nm | Very Large Telescope FORS2 |
| Optisk v | 557 nm | Very Large Telescope FORS2 |
| Optisk R | 655 nm | Very Large Telescope FORS2 |
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