Free Astronomy Magazine September-October 2020

12 SEPTEMBER-OCTOBER 2020 STELLAR EVOLUTION giant, accelerating its rotation. Wheeler cal- culated that, to justify Betelgeuse’s current 15 km/s rotation speed, the mass of the de- stroyed star had to be comparable to that of the Sun. Also knowing that the loss of mass from a supergiant oc- curs at a typical speed of 10 km/s, Wheeler has come to speculate that the arches preced- ing Betelgeuse may have formed as a re- sult of that dramatic event. Parallel to the observa- tions of the nebular structures surrounding Betelgeuse, attempts have obviously multi- plied to measure the distance to the star through various techniques, all without reaching a common value. Indeed, even today, depending on the authoritative The angular momentum of the orbital mo- tion of the companion would be trans- ferred to the outermost layers of the super- C omparisons that highlight the different brightness of Betelgeuse be- fore and during the extraordinary minimum. Left, two photos from February 2016 and 31 December 2019. [Brian Ottum/EarthSky] Below, two im- ages taken with the VLT’s SPHERE instrument in January 2019 and December 2019. [ESO/M. Mon- targès et al.]