Astronomie/Exploration de l'Univers

R136a1 is a blue hypergiant star of R136, a super star cluster in the Large  Megallanic Cloud. It is estimated to be 265 solar masses making it the most massive star but not the largest. The largest star being VY Canis Majoris. R136a1 is also the most luminous star known, with a luminosity of 8,700,000 times the luminosity of the Sun. The surface temperature of the star is about 50,000 K.

The Scutum–Centaurus Arm (also known as Scutum-Crux arm), is a long, diffuse curving streamer of stars, gas and dust that spirals outward from the proximate end of the Milky Way's central bar. The Milky Way has been assumed since the 1950s to have four spiral arms although the evidence for this has never been strong.[1] In 2008, observations using the Spitzer Space Telescope failed to show the expected density of red clump giants that in the direction of the Sagittarius and Norma arms.[2] In January 2014, a 12-year study into the distribution and lifespan of massive stars[3] and a study of the distribution of masers and open clusters [4] both found evidence for four spiral arms.

The Scutum–Centaurus Arm lies between the minor Carina–Sagittarius Arm and the major Perseus Arm. The Scutum–Centaurus Arm arm starts near the core as the Scutum Arm, then gradually turns into the Centaurus Arm.[5]

The region where the Scutum–Centaurus Arm arm connects to the bar of the galaxy is rich in star-forming regions. In 2006 a large cluster of new stars containing 14 red supergiant stars was discovered there and named RSGC1. In 2007 a cluster of approximately 50,000 newly formed stars named RSGC2 was located only a few hundred light years from RSGC1. It is thought to be less than 20 million years old and contains 26 red supergiant stars, the largest grouping of such stars known.[6] Other clusters in this region include RSGC3 and Alicante 8.[7

Bras Écu-Croix

Structure de la Voie lactée.
Sur ce diagramme, le Soleil est représenté par un point jaune.
Le bras Écu-Croix (également appelé bras du Centaure) est un bras spiral de la Voie lactée. Il se trouve entre le bras Sagittaire-Carène et le bras de la Règle.

Le section du bras débutant près du centre galactique constitue le bras de l’Écu, qui devient le bras de la Croix lorsqu’on s’éloigne du centre.

La région dans laquelle le bras Écu-Croix croise le bulbe central est riche en étoiles naissantes. En 2006, un grand amas d’étoiles jeunes contenant 14 supergéantes rouges, appelé RSGC1, fut découvert. En 2007, un nouvel amas fut découvert, RSGC2, à seulement quelques centaines d’années-lumière du précédent. Ce dernier contient environ 50 000 étoiles récemment formées, et est âgé de moins de 20 millions d’années. 26 supergéantes ont été découvertes dans ce seul amas, ce qui en fait le plus grand groupement de telles étoiles connu à ce jour1.

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