Cartographier une collision de galaxies
Cette image inhabituelle révèle les conséquences d’une collision catastrophique entre deux galaxies qui s’est produite environ il y a un milliard d’années. Le résultat ? une singulière galaxie à la forme bizarre appelée NGC 7252, et curieusement surnommée la galaxie “Atomes pour la paix”.
NGC 7252 résulte de la fusion de deux galaxies et en son coeur se trouve une fascinante mini-spirale - un disque en rotation qui subit une intense formation stellaire. Avec le spectrographe VIMOS (VIsible Multi-Object Spectrograph) installé sur le VLT (Very Large Telescope) d’ESO, les astronomes ont pu mesurer le mouvement du gas à l’intérieur de ce disque, cartographiant sa rotation. Les régions rouges indiquent où le gas s’éloigne de nous alors que les régions bleues montrent où le gas s’approche de nous. Ensemble ces couleurs révèlent le centre en rotation continue de la galaxie et mettent aussi l’accent sur les deux flux de gas chaud au nord-ouest et au sud-est de la région centrale. Des études précédentes suggéraient que la spirale centrale tournait en sens inverse par rapport au reste de la galaxie, mais en comparant le mouvement des étoiles autour de la galaxie avec celui du gas ionisé par les nouvelles étoiles à peine formées dans la mini-spirale, nous savons maintenant qu’ils tournent en fait dans la même direction.
Une cartographie aussi détaillée est possible grâce à la technique IFU (Integral Field Unit) avec VIMOS, permettant aux astronomes d’étudier le gas dans NGC 7252 avec une vision complète à mosaïque. Comme une mouche observe le monde, une IFU divise son sujet en beaucoup de cellules, ou pixels, et génère un spectre pour chacun d’elles. L’information finale est arrangée dans un cube de données 3D, qui est particulièrement utile pour étudier les objects étendus en une seule exposition.
En faisant glisser la poignée verte, cette nouvelle carte du VLT peut être superposée à une image plus vieille du télescope spatial Hubble de la NASA et d’ESA, qui combine la beauté visuelle de la galaxie à la complexité de sa mécanique interne.
Crédit:
NASA & ESA, Acknowledgement: Judy Schmidt (Geckzilla)
À propos de l'image
Identification: | potw1806a |
Langage: | fr-be |
Type: | Observation |
Date de publication: | 5 février 2018 06:00 |
Taille: | 2461 x 1614 px |
À propos de l'objet
Nom: | NGC 7252 |
Type: | Local Universe : Galaxy : Type : Interacting |
Distance: | 220 million années lumière |
Constellation: | Aquarius |
Fonds d'écran
Coordinates
Position (RA): | 22 20 44.69 |
Position (Dec): | -24° 40' 42.33" |
Field of view: | 1.63 x 1.07 arcminutes |
Orientation: | North is 0.1° left of vertical |
Couleurs & filtres
Domaine | Longueur d'onde | Télescope |
---|---|---|
Visible u | 336 nm | Hubble Space Telescope WFC3 |
Visible g | 475 nm | Hubble Space Telescope WFC3 |
Infrarouge J | 1.1 μm | Hubble Space Telescope WFC3 |
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