In late 2019 to early 2020, the supergiant star Betelgeuse dimmed.[ESO/M. Montargès et al.]
When the star Betelgeuse dimmed in late 2019 to early 2020, the astronomy community began to wonder if the star would soon explode as a supernova. It’s a red supergiant star, which is a late evolutionary stage of a star some 8 to 30 times the mass of the Sun. And Betelgeuse is destined to explode as a supernova; perhaps this was the start? But the star brightened again. Crisis averted.
Most stars are too far away from us, too small, or too faint (or some combination of the three) for telescopes to resolve them. But Betelgeuse, the bright orange star at constellation Orion’s shoulder, is about 700 light-years away and a supergiant star. Astronomers for over a decade have been able to resolve some details of Betelgeuse’s surface, and that ability let researchers learn what was happening with this star during its “great dimming” of 2019–2020.
A new study, published last week in the journal Nature, suggests this dimming was the result of an enormous dust cloud shrouding roughly one quarter of the star’s surface. This study used multiple instruments at the European Southern Observatory’s Very Large Telescope (VLT). The researchers hypothesized and computationally modeled several scenarios that could have explained the dimming. They determined the most likely scenario is that convention in the star brought up a large bubble of cooler gas, which was ejected from the star, and once cooled enough condensed to dust.
Liz Kruesi is the editor of Mercury magazine and Mercury Online. She has shared the stories of astronomy since 2005. Read more articles by Liz.