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On the trail of a disk around a star
AMBER observes Betelgeuse and reveals how supergiant stars lose mass
30 juillet 2009
Betelgeuse — the second brightest star in the constellation of Orion (the Hunter) — is a red supergiant, one of the biggest stars known, and almost 1000 times larger than our Sun . It is also one of the most luminous stars known, emitting more light than 100 000 Suns. Such extreme properties foretell the demise of a short-lived stellar king. With an age of only a few million years, Betelgeuse is already nearing the end of its life and is soon doomed to explode as a supernova. When it does, the supernova should be seen easily from Earth, even in broad daylight.
- A plume on Betelgeuse artist’s impression)
- This artist’s impression shows the supergiant star Betelgeuse as it was revealed thanks to different state-of-the-art techniques on ESO’s Very Large Telescope. The scale in units of the radius of Betelgeuse as well as a comparison with the Solar System is also provided.
Red supergiants still hold several unsolved mysteries. One of them is just how these behemoths shed such tremendous quantities of material — about the mass of the Sun — in only 10 000 years. To arrive at a solution, astronomers needed to probe the behemoth in still finer detail. Keiichi Ohnaka from the Max Planck Institute for Radio Astronomy in Bonn, Germany, and his colleagues used the AMBER instrument on ESO’s Very Large Telescope Interferometer, which combines the light from three 1.8-metre Auxiliary Telescopes of the VLT, these astronomers obtained observations as sharp as those of a giant, virtual 48-metre telescope.
The AMBER observations revealed that the gas in Betelgeuse’s atmosphere is moving vigorously up and down, and that these bubbles are as large as the supergiant star itself. Their unrivaled observations have led the astronomers to propose that these large-scale gas motions roiling under Betelgeuse’s red surface are behind the ejection of the massive plume into space.
For more information :
the ESO press release 27/09
The MPIfR press release SP / 2009 (147) (in German)
the article published in Astronomy and Astrophysics, vol. 503, p. 1830 : Spatially resolving the inhomogeneous structure of the dynamical atmosphere of Betelgeuse with VLTI/AMBER by K. Ohnaka, K.-H. Hofmann, M. Benisty, A. Chelli, T. Driebe, F. Millour, R. Petrov, D. Schertl, Ph. Stee, F. Vakili, G. Weigelt
 If Betelgeuse were at the centre of our Solar System it would extend out almost to the orbit of Jupiter, engulfing Mercury, Venus, Earth, Mars and the main asteroid belt.