A cold spot and a stellar burp led to strange dimming of Betelgeuse

Dust is the primary culprit, but it is linked to the brief emergence of a cold spot.As Ars' John Timmer reported last year, Betelgeuse is one of the closest massive stars to Earth, about 700 light years away. Combined with some timely ground observations, this UV data indicated that a big burp that formed a cloud of dust near the star may have caused the star to get darker."With Hubble, we could see the material as it left the star's surface and moved out through the atmosphere, before the dust formed that caused the star to appear to dim," said Andrea Dupree, an astronomer at the Harvard-Smithsonian Center for Astrophysics who made those observations. She is also a co-author on the new paper.The findings last year showed that an outer layer of the star, called the photosphere, had begun unevenly accelerating outward right before Betelgeuse began to dim. "For once, we were seeing the appearance of a star changing in real time on a scale of weeks," said co-author Miguel Montargès, from the Observatoire de Paris, France, and KU Leuven, Belgium.Those images, combined with earlier observations in January and December 2019, allowed astronomers to directly witness the stardust formation, matching the observations of Dupree and her colleagues last year.