Nouvelles idées sur les disques de débris
En utilisant 39 des 66 antennes d’ALMA (Atacama Large Millimeter/submillimeter Array), situé à 5000 mètres d’altitude sur le plateau de Chajnantor dans les Andes chiliennes, les astronomes ont pu détecter du monoxyde de carbone (CO) dans le disque de débris autour d’une étoile de type F. Malgré que le dioxyde de carbone soit la seconde molécule plus abondante dans le milieu interstellaire après la l’hydrogène moléculaire, c’est la première fois que le CO est détecté atour d’une étoile ce type. L’étoile, appelée HD 181327, est un membre du groupe mouvant de Beta Pictoris, situé à presque 170 années-lumière de la Terre.
Jusqu’à présent, la présence de CO a été détectée seulement autour de peu d’étoiles de type A, considérablement plus massive et plus lumineuse que HD 181327. Grâce à la superbe résolution spatiale et à la sensibilité qu’offre l’observatoire ALMA, les astronomes sont maintenant capables de capturer cet étonnant anneau de fumée et de cartographier la densité spatiale du CO à l’intérieur du disque.
L’étude des disques de débris est une des possibilités pour caractériser les systèmes planétaires et les résultats de la formation de planètes. Le gas CO se trouve à la même position que les grains de poussière dans l’anneau de débris et on pense qu’il s’est formé récemment. Des collisions destructives des planétésimaux de glace dans le disque sont des sources possibles du réapprovisionnement continu du gas CO. Les collisions dans les disques de débris typiquement requirent une perturbation gravitationnelle des corps de glace par des objets plus grands pour pouvoir atteindre des vitesses de collision suffisantes. En outre la composition du CO des planétésimaux glacés dans le disque est consistente avec les comètes de notre système solaire. Cette deuxième possibilité pour l’origine du gas CO suggère que les comètes de glace pourraient être comunes autour d’étoiles similaires à notre Soleil, ce qui a de fortes implications pour la pertinence de la vie sur les planètes extrasolaires terrestres.
Les résultats ont été publiés dans le journal Monthly Notices of the Royal Astronomical Society avec le titre “Exocometary gas in the HD 181327 debris ring” par S. Marino et al.
ESO/Marino et al.
À propos de l'image
| Identification: | potw1621a |
| Langage: | fr-be |
| Type: | Observation |
| Date de publication: | 23 mai 2016 06:00 |
| Taille: | 2000 x 2000 px |
À propos de l'objet
| Nom: | HD 181327 |
| Type: | Milky Way : Star : Circumstellar Material : Disk : Debris |
| Distance: | 170 années lumière |
| Constellation: | Telescopium |
Fonds d'écran
Coordinates
| Position (RA): | 19 22 58.99 |
| Position (Dec): | -54° 32' 18.21" |
| Field of view: | 0.13 x 0.13 arcminutes |
| Orientation: | North is -0.0° left of vertical |
Couleurs & filtres
| Domaine | Télescope |
|---|---|
| Millimétrique 220 GHz | Atacama Large Millimeter/submillimeter Array |
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