Prises dans une spirale
L'image montre une paire de galaxies spirales superposées, NGC 3314a et b, en haut à gauche, prises dans une majestueuse danse cosmique - capturée par le VLT Survey Telescope (VST) de l'ESO.
Mais ne vous laissez pas tromper par la perspective ! En fait, elles ne sont pas du tout en interaction. Les deux galaxies, situées entre 117 et 140 millions d'années-lumière dans la constellation de l'Hydre, ne sont en fait pas physiquement liées et ne semblent se chevaucher que vues de la Terre. Cet alignement unique donne aux astronomes la possibilité de mesurer de nombreuses propriétés des galaxies, comme la façon dont la poussière absorbe la lumière des étoiles, et donc de mieux comprendre leur composition et leur évolution.
Un autre secret se cache dans cette image si vous regardez attentivement la région en bas à droite : au-delà de cette danse cosmique étonnante, vous trouverez une faible tache jaunâtre, la signature d'une galaxie ultra-diffuse (UDG). Les UDG sont des objets aussi grands que la Voie lactée, mais avec 100 à 1000 fois moins d'étoiles. Ces galaxies sont extrêmement ténues et manquent de gaz pour former des étoiles, ce qui les fait apparaître comme une tache dans le ciel nocturne. Cette UDG, nommée UDG 32, est l'une des galaxies les plus faibles et les plus étalées de l'amas Hydra I.
Cette image a été prise dans le cadre d'un projet beaucoup plus vaste, le VST Early-type Galaxy Survey (VEGAS), dont l'objectif est d'étudier les structures très faibles dans les amas de galaxies - de grands groupes de galaxies maintenues ensemble par la gravité. L'étude, dirigée par Enrichetta Iodice de l'Istituto Nazionale di Astrofisica en Italie, suggère que UDG 32 pourrait s'être formée à partir des filaments issus de NGC 3314a, mais d'autres observations sont nécessaires pour le confirmer.
Crédit:ESO/Iodice et al.
À propos de l'image
| Identification: | potw2145a |
| Langage: | fr |
| Type: | Observation |
| Date de publication: | 8 novembre 2021 06:00 |
| Taille: | 1717 x 1725 px |
À propos de l'objet
Fonds d'écran
Coordinates
| Position (RA): | 10 37 8.92 |
| Position (Dec): | -27° 41' 55.30" |
| Field of view: | 6.01 x 6.04 arcminutes |
| Orientation: | North is 0.2° left of vertical |
Couleurs & filtres
| Domaine | Longueur d'onde | Télescope |
|---|---|---|
| Visible g | 480 nm | VLT Survey Telescope OmegaCAM |
| Visible r | 625 nm | VLT Survey Telescope OmegaCAM |
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