Le trou d’ALMA dans l’univers
Les évènements autour du Big Bang étaient si cataclysmiques qu’ils ont laissé une trace indélébile dans la structure du cosmos. Nous pouvons détecter des cicatrices aujourd’hui en observant la lumière la plus ancienne dans l’univers. Lorsqu’elle a été créée il y a environ 14 milliards d’années, cette lumière - qui existe aujourd’hui comme la faible radiation à micro-ondes et qui s’appelle donc le fond cosmique de micro-ondes (en anglais, cosmic microwave background, CMB) - s’est dilatée pour se répandre dans tout le cosmos, la remplissant de photons détectables.
Le CMB peut être utilisé pour mesurer le cosmos avec l’effet Sunyaev-Zel’dovich (SZ) qui a été observé la première fois il y a un peu plus de 30 ans. Nous mesurons le CMB sur la Terre quand ses photons à micro-ondes qui le constituent voyagent vers nous à travers l’espace. Pendant leur voyage, ils passent à travers des amas de galaxies qui contiennent des électrons à haute énergie. Ces électrons augmentent l’énergie des photons. Détecter ces photons à haute énergie avec nos télescopes est difficile mais important - ils peuvent aider les astronomes à comprendre quelques propriétés fondamentales de l’univers, comme par exemple la position et la distribution des amas denses de galaxies.
Cette image montre les premières mesures de l’effet thermique de Sunyaev-Zel’dovich avec ALMA (Atacama Large Millimeter/submillimeter Array) au Chili (en bleu). Les astronomes ont combiné les observations des antennes de 7 mètres et de 12 mètres d’ALMA pour produire l’image la plus détaillée possible. La cible était un des plus massifs amas de galaxies connu, RX J1347.5–1145, dont le centre se trouve ici dans le “trou” noir dans les observations d’ALMA. La distribution d’énergie des photons du CMB se déplace et apparaît comme une diminution de température à la longueur d’onde observée par ALMA, par conséquent une tache sombre est observée dans cette image à la place de l’amas.
Crédit:
ALMA (ESO/NAOJ/NRAO)/T. Kitayama (Toho University, Japan)/ESA/Hubble & NASA
À propos de l'image
| Identification: | potw1708a |
| Langage: | fr-ch |
| Type: | Observation |
| Date de publication: | 20 février 2017 06:00 |
| Taille: | 3816 x 3559 px |
À propos de l'objet
| Type: | Early Universe : Cosmology |
| Constellation: | Virgo |
Fonds d'écran
Coordinates
| Position (RA): | 13 47 30.65 |
| Position (Dec): | -11° 45' 18.95" |
| Field of view: | 1.91 x 1.78 arcminutes |
| Orientation: | North is 130.7° right of vertical |
Couleurs & filtres
| Domaine | Longueur d'onde | Télescope |
|---|---|---|
| Millimétrique 92 GHz | 3.258613 mm | Atacama Large Millimeter/submillimeter Array Band 3 |
| Visible g | 475 nm | Hubble Space Telescope ACS |
| Visible B | 435 nm | Hubble Space Telescope ACS |
| Visible V | 606 nm | Hubble Space Telescope ACS |
| Visible r | 625 nm | Hubble Space Telescope ACS |
| Visible i | 775 nm | Hubble Space Telescope ACS |
| Visible z | 850 nm | Hubble Space Telescope ACS |
| Infrarouge J | 1.1 μm | Hubble Space Telescope WFC3 |
| Infrarouge H short | 1.6 μm | Hubble Space Telescope WFC3 |
| Visible I | 814 nm | Hubble Space Telescope ACS |
| Infrarouge J | 1.1 μm | Hubble Space Telescope WFC3 |
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