Betelgeuse’s dimming explained

The star’s exceptional dimness earlier this year was observed during a Hubble study

‘sneeze’ was responsible for Betelgeuse’s unprecedented period of dimming at the beginning of the year, according to a recent update from astronomers who had been monitoring the star. They revealed that it had experienced an outburst of a huge cloud of material just before it began to dim, hiding a quarter of the star from view.

Betelgeuse is a red giant and a favourite for astronomers, partly due to its prominence in the constellation of Orion and partly because it’s expected to go supernova at any time in the next 100,000 years. Its brightness is known to vary slightly, but in October 2019 it dimmed dramatically and by mid-February it was around three times fainter than normal.

The star then recovered, and by April it was as bright as ever, leaving astronomers to wonder what had caused the massive reduction in brightness. Fortunately for those investigating, the

A stellar

star had been monitored for months running up to the episode by the Hubble Space Telescope. A three-year study into Betelgeuse’s outer atmosphere has been regularly monitoring the star since early 2019, examining it in the ultraviolet wavelengths needed to see the hottest materials surrounding the star.

“With Hubble, we had previously observed hot convection cells on the surface of Betelgeuse and in the [autumn] of 2019 we discovered a large amount of dense hot gas moving outwards through Betelgeuse’s extended atmosphere,” says Andrea Dupree from the Harvard-Smithsonian Center for Astrophysics. “We think this gas cooled down millions of miles outside the star to form the dust that blocked the southern part of the star, which was imaged in January and February.” www.hubblesite.org