NASA telescope discovers the cause of Betelgeuse’s mysterious dimming

In the Before Times, when the coronavirus had just begun his furious march across the world, our problems were much further away. About 640 light-years away, in fact. Astronomers observe Betelgeuse, a red redundant star, had amazed her by his mysterious dimness. Some believed that the event, which lasted from November 2019 to February 2020, was a portent of doom signaling the coming explosion of the star. But then the dimming stopped abruptly.

Thanks to observations by NASA’s Hubble Space Telescope, we might know why.

A new study, published in The Astrophysical Journal on Thursday (and accessible at arXiv), examined ultraviolet light emitted by Betelgeuse during the “Great Dimming” event using the Hubble Space Telescope. Fortunately, the dimming event happened just as Hubble scientists were trying to observe Betelgeuse with the telescope, which provided an opportunity to understand why the star began to darken.

Betelgeuse is a massive star, about 700 times larger than our Sun. If you threw it into our solar system, it would be Mercury, Venus, Earth, Mars, the different worlds of the asteroid belt heel and Jupiter would also end up as a snack. And it comes at the end of its life cycle, sometimes in the next 100,000 years. When the supergiant began to dim last year, there were some believers who thought the process of explosion might have begun.

The Hubble observations suggest otherwise. By looking at Betelgeuse for UV wavelengths, researchers were able to get a better look at the surface and atmosphere of the star. She discovered a mass of bright, hot material that ran out of the southern hemisphere of the star, about 200,000 miles per hour and eventually emitted into space.

“This material was two to four times brighter than the star’s normal brightness,” Andrea Dupree, associate director at the Harvard-Smithsonian Center for Astrophysics and lead author on the study, said in a NASA release. About a month after the eruption, the southern part of Betelgeuse evaporated markedly, she said.

Dupree and her team believe that this material may have begun to cool as it passed through space, forming a dense cloud of dust that partially obscured Betelgeuse. It just so happens that Earth was in the perfect position to “see” the dust cloud ahead, as if Betelgeuse were shooting the dust cloud directly at us. If it happened on the opposite side of Betelgeuse, we would probably never know.

Explosive eruptions are expected from stars at the end of their lives and when they die or “go supernova”, they release a shock wave that injects elements into space. The activity is critical to fill space with heavy elements such as carbon, which can then become new stars elsewhere in the universe, so these stars are critical to the cosmic Circle of Life.

Betelgeuse, however, is still acting a little strangely. Observations from NASA’s Stereo spacecraft observed the supergiant between the end of June and the beginning of August and noticed that Betelgeuse unexpectedly dimmed. NASA notes that further observations will be made in late August, when the star returns to the night sky and can be seen again through telescopes.