An artist’s impression of an eruption on on the surface of the red supergiant Betelgeuse. As the hot, dense material moved away, it cooled and formed a vast dust cloud that would have partially obscured the giant star, blocking light and causing it
In October 2019, the red supergiant Betelgeuse, the brilliant red star in Orion’s left shoulder, suddenly started dimming. By February 2020, the giant star had dimmed to less than a third of its normal brightness, prompting widespread astronomical interest and internet speculation on the possible cause.
Now, using ultraviolet observations by the Hubble Space Telescope, researchers say the dimming likely was caused by an enormous eruption that ejected a vast cloud of superheated material that then cooled, forming a dust cloud that blocked out light from about a quarter of of Betelgeuse’s surface.
“With Hubble, we see the material as it left the star’s visible surface and moved out through the atmosphere, before the dust formed that caused the star to appear to dim,” said Andrea Dupree, associate director of the Harvard-Smithsonian Center for Astrophysics. “We could see the effect of a dense, hot region in the southeast part of the star moving outward.”
“This material was ...