ALMA observe la naissance des étoiles
Avec leurs bras lumineux spectaculaires, les grandes galaxies à spirale semble attirer toute l’attention - mais NGC 6822, une galaxie naine, irrégulière et barrée, prouve que les galaxies à spirale normales n’ont pas le monopole de la beauté. Aussi appelée la galaxie de Barnard, NGC 6822 est située dans la constellation du Sagittaire à une distance de seulement 1,6 million d’années-lumière; elle déborde de riches régions de formation stellaire. Cette nouvelle image est un composé de vieilles observations réalisées avec le Wide Field Imager monté sur le télescope de 2,2 mètres de diamètre de MPG/ESO à l’observatoire La Silla d’ESO et de nouvelles observations prises par ALMA (Atacama Large Millimeter/submillimeter Array). Les zones observées par ALMA sont soulignées dans cette image peuvent être examinées en détail ici.
Les observations d’ALMA révèlent la structure des nuages de formation stellaire avec une résolution spatiale jamais atteinte. Les observations dans notre propre galaxie ont montré que les étoiles se forment dans les noyaux denses de nuages géants d’hydrogène moléculaire, les seuls endroits où le gas est assez froid pour s’effondrer sur lui-même due à sa propre gravité. Ces conditions permettent aussi d’encourager la formation d’autres molécules, comme le monoxyde de carbone, qui est un outil indispensable pour aider les astronomes à détecter l’hydrogène moléculaire galactique.
Jusqu’à récemment les astronomes étaient capables d’observer les détails des régions de formation stellaire seulement dans notre galaxie la Voie lactée - mais maintenant la vue perçante d’ALMA permet d’ouvrir une fenêtre sur la formation d’étoiles dans les autres galaxies. L’analyse de ces observations révèlent que, au contraire de notre galaxie, les molécules se concentrent dans des petits coeurs denses de gas. Cela explique pourquoi c’était si difficile d’observer des régions de formation stellaire extragalactique, spécialement dans les galaxies de petite masse et de bas contenu en métaux. ALMA a aussi trouvé que les coeurs dans NGC 6822 se comportent de manière remarquablement similaire aux régions de formation stellaire dans la Voie lactée, indiquant que la physique de ce phénomène dans les galaxies de petite masse ressemble à ce que l’on peut observer dans notre galaxie.
Liens
- Nuage de formation stellaire dans NGC 6822
- ALMA observe des nuages dans NGC 6822
- La galaxie de Barnard observée avec le télescope 2,2 mètre de MPG/ESO
- Publication de recherche par Schruba et al.
- Communiqué de presse de MPE
- Communiqué de presse de NOVA
ESO, ALMA (ESO/NAOJ/NRAO)/A. Schruba, VLA (NRAO)/Y. Bagetakos/Little THINGS
À propos de l'image
| Identification: | potw1711a |
| Langage: | fr-ch |
| Type: | Collage |
| Date de publication: | 13 mars 2017 06:00 |
| Taille: | 5868 x 6480 px |
À propos de l'objet
| Nom: | NGC 6822 |
| Type: | Milky Way : Galaxy : Type : Irregular Milky Way : Galaxy : Size : Dwarf |
| Distance: | 2 million années lumière |
Image Formats
Fonds d'écran
Couleurs & filtres
| Domaine | Longueur d'onde | Télescope |
|---|---|---|
| Visible B | 456 nm | MPG/ESO 2.2-metre telescope WFI |
| Radio HI | 21 cm | Very Large Array |
| Visible V | 539 nm | MPG/ESO 2.2-metre telescope WFI |
| Visible R | 651 nm | MPG/ESO 2.2-metre telescope WFI |
| Millimétrique CO/230 GHz | 1.3 mm | Atacama Large Millimeter/submillimeter Array Band 6 |
| Visible H-alpha | 658 nm | MPG/ESO 2.2-metre telescope WFI |
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