Free Astronomy Magazine September-October 2020

10 SEPTEMBER-OCTOBER 2020 STELLAR EVOLUTION Two years after these first revelations, as- tronomers were able to verify that the ma- terial surrounding Betelgeuse extends far beyond the boundaries already identified. New images obtained in the mid-infrared by the VISIR instrument (installed on VLT’s Unit Telescope 3) indeed showed an im- mense nebular structure, extended up to about 60 billion km from the star, equiva- lent to over two light-days. Those same im- ages showed for the first time that the plumes previously observed near the pho- tosphere are probably connected to the ex- ternal nebular structure. The latter also has an asymmetrical shape, supporting the hy- pothesis according to which the star would not lose mass uniformly from the surface. The environment surrounding Betelgeuse proved to be even more complex when, at the beginning of 2013, images obtained the year before in the far-infrared by Leen Decin (KU Leuven, Belgium) with ESA’s Herschel Space Telescope were presented. In them, it is evident that the stellar winds I mages obtained by VISIR of the nebular structure surrounding Betelgeuse up to distances of tens of billions of km. The one on the left was taken in 2011; the one on the right during the recent light fall, in December 2019. The central regions of the two images have been obscured. Betelgeuse is in- dicated in the center. [ESO/P. Kervella/ M. Mon- targès et al., Ac- knowledgement Eric Pantin] To the side, the arches preceding Betelgeuse, pho- tographed by the Herschel Space Telescope. [ESA/ Herschel/PACS/L. Decin et al./Uni- versity of Leuven]