Annonce

ALMA en extension maximale fournit de spectaculaires images

7 avril 2015

Les images d'une netteté inégalée montrant l'anneau gravitationnel d'Einstein presque parfait d'une galaxie lointaine et de la surface de l'astéroïde Juno ont été récemment prises par le Grand Réseau millimétrique / submillimétrique d'Atacama (ALMA). Ces superbes photos ont été prises à la fin de 2014 dans le cadre de la Long Baseline Campaign d'ALMA, qui a testé avec succès et vérifié la capacité du télescope à voir les détails les plus fins. Ce résultat est obtenu lorsque les antennes sont à leur plus grand écartement: jusqu'à 15 km de distance.

Cinq cibles ont été choisies pour l'étude pendant la Long Baseline Campaign d'ALMA. Elles comprenaient le disque protoplanétaire HL Tauri, la galaxie SDP.81 déformée par lentille gravitationnelle, l'astéroïde Juno, l'étoile Mira et le quasar 3C138. L'Astrophysical Journal Letters a publié quatre articles scientifiques écrits par des représentants de l'ensemble de l'équipe internationale des partenaires d'ALMA, détaillant ces observations.

SDP.81 est une galaxie active d'étoiles en formation vue au moment où l'univers n'avait qu'environ 15% de son âge actuel. Elle est déformée par une galaxie massive en avant-plan relativement proche à environ quatre milliards d'années-lumière de distance. La lentille gravitationnelle a créé un anneau d'Einstein presque parfait. La résolution d'ALMA sur cette cible avec la plus grande étendue au sol dépasse celle de tous les autres télescopes qui ont l'observé, y compris le télescope spatial Hubble de la NASA / ESA , et révèle plus de fines structures dans l'anneau comme jamais vu auparavant.

Le second objectif était beaucoup plus proche de la Terre. Une série d'images réalisées avec ALMA fournit une vue sans précédent de la surface de Juno, l'un des plus grands éléments de la ceinture principale d'astéroïdes du système solaire. Liées ensemble dans une brève animation, ces images haute résolution montrent la rotation de l'astéroïde dans les longueurs d'onde millimétriques.

La séquence complète des observations d'ALMA a été effectuée pendant une durée de quatre heures, quand Juno était à environ 295 millions de kilomètres de la Terre. La résolution des nouvelles observations d'ALMA est d'une amélioration considérable par rapport aux observations précédemment faites aux longueurs d'onde similaires et est suffisante pour résoudre clairement la forme irrégulière de l'astéroïde et potentiellement de discerner les éléments les plus importants de la surface.
Les cinq objets ont été choisis pour montrer le potentiel scientifique d'ALMA, le plus grand observatoire au sol dans le monde, dans sa configuration la plus étendue.

Plus d'information

Le grand réseau millimétrique / submillimétrique d'Atacama (ALMA), un projet astronomique international, est un partenariat entre l'ESO, la Fondation nationale pour la science (NSF) et les Instituts nationaux des sciences naturelles (NINS) du Japon en coopération avec la République du Chili. ALMA est financé par l'ESO au nom de ses états membres, par la NSF en coopération avec le Conseil national de recherches du Canada (CNRC) et le Conseil national des sciences de Taiwan (NSC) et par le NINS en coopération avec l'Academia Sinica (AS) à Taïwan et l'Institut Coréen d'astronomie et de l'espace (KASI). La Construction et l'exploitation d'ALMA est dirigée par l'ESO au nom de ses États membres; par l'Observatoire national de radioastronomie (NRAO), géré par l'Associated Universities, Inc. (AUI), au nom de l'Amérique du Nord; et par l'Observatoire astronomique national du Japon (NAOJ) au nom de l'Asie orientale. L'Observatoire ALMA mixte (JAO) assure le leadership et la gestion unifiée de la construction, la mise en service et l'exploitation d'ALMA.

Liens

Photos de ALMA

Prépublication concernant les observations d'ALMA de SDP.81

Prépublication concernant les observations d'ALMA de Juno

Prépublication concernant les observations d'ALMA de HL Tauri

Contacts

Richard Hook

ESO, Public Information Officer

Garching bei München, Allemagne

Tel: +49 89 3200 6655
Portable: +49 151 1537 3591
Email: rhook@eso.org

À propos de l'annonce

Identification:ann15028

Images

ALMA image of the gravitationally lensed galaxy SDP.81
ALMA image of the gravitationally lensed galaxy SDP.81
Seulement en anglais

Vidéos

Animation of the asteroid Juno as imaged by ALMA
Animation of the asteroid Juno as imaged by ALMA
Seulement en anglais

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