Free Astronomy Magazine September-October 2020

SEPTEMBER-OCTOBER 2020 of its outer layers over semi- regular periods − typical be- havior of a very old and massive star. These jolts are a complication for anyone trying to accurately measure the physical properties of Betelgeuse. As our understanding of stel- lar evolution progressed, as- tronomers realized that the turbulent activity of Betel- geuse should have caused a conspicuous loss of mass, quantifiable as one solar mass every 10,000 years. The gravitational attraction ex- erted on the outermost stel- lar layers is indeed so mild that the thrust of the con- vective cells that transport heat from the core towards the surface is sufficient to throw into outer space mat- A bove, a com- posite image of the star field around Betelgeuse. [ESO/Digitized Sky Survey 2. Ack D. De Martin] On the left, the first detailed image of Betel- geuse's surface, obtained in near- infrared by the IOTA interferome- ter at the Paris Observatory. The resolution is 9 mas. The differ- ences in bright- ness are attribut- able to convective phenomena. [Hau- bois/Perrin (LESIA, Observatoire de Paris) 2010]