Annonce
Les observations de MUSE permettent de façon unique de revoir l’explosion d’une supernova
25 novembre 2015
Des astronomes ont utilisé le spectrographe multi-objets MUSE (Multi Unit Spectroscopic Explorer) sur le VLT (Very Large Telescope) d’ESO à l’observatoire de Paranal pour profiter d’une opportunité unique de tester leur compréhension des amas massifs de galaxies. Ils ont réussi à faire la toute première prédiction d’un événement astronomique dans l’univers distant avant qu’il ne devienne visible. Les images de l’amas de galaxies MACS J1149+2223 observé avec le télescope spatial Hubble de la NASA/ESA en novembre 2014 ont révélé une distante explosion d’étoile - une supernova - comme jamais observée. Surnommée Refsdal [1], elle est la première supernova séparée en quatre images distinctes grâce au processus de lentille gravitationnelle. Elle forme une croix d’Einstein presque parfaite autour d’une galaxie de l’amas.
La lentille gravitationnelle est une conséquence de la théorie de la relativité générale d’Einstein. La travail scientifique qui décrit les équations de ce changement fondamental dans notre compréhension de la gravité a été publié le 25 novembre 1915, il y a exactement un siècle.
Des mesures essentielles des distances précises des galaxies de l’amas dans MACS J1149+2223 ont été faites avec MUSE au début de 2015. Elles ont permis aux astronomes de modéliser la distribution de masse à l’intérieur de l’amas géant de galaxies de façon extrêmement précise. Cela a permis de prédire quand et ou une autre image de la distante supernova apparaitra - un replay instantané sur le plus grand écran imaginable.
Parce que la lumière qui forme les images multiples de la supernova prend des chemins de différentes longueurs vers la Terre, elles apparaissent à des époques différentes et à des endroits différents sur le ciel. En utilisant toutes les données disponibles de MUSE, en combinaison avec les observations de Hubble, une équipe d’astronomes dirigée par Claudio Grillo (Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Danemark) a prédit qu’un replay aura son maximum de luminosité entre mars et juin 2016, avec une possible première détection à la fin de 2015. Ils peuvent aussi anticiper non seulement quand et ou la supernova sera à nouveau visible, mais aussi quelle sera sa luminosité approximative.
Hubble observe périodiquement l’amas dans l’espoir de capturer cet événement unique, ce qui permettra aux astronomes de tester leur modèle.
Ces observations démontre le rôle vital que MUSE et le VLT ont joué dans l’exploration de l’univers distant, ainsi que la synergie entre Hubble et les observatoires à terre.
Notes
[1] Cette supernova est appelée ainsi en l’honneur de feu l’astronome norvégien Sjur Refsdal.
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