Caption This illustration plots changes in the brightness of the red supergiant star Betelgeuse, following the titanic mass ejection of a large piece of its visible surface. The escaping material cooled to form a cloud of dust that temporarily made the star look dimmer, as seen from Earth. This unprecedented stellar convulsion disrupted the monster star’s 400-day-long oscillation period that astronomers had measured for more than 200 years. The interior may now be jiggling like a plate of gelatin dessert. Credit: ILLUSTRATION: NASA, ESA, Elizabeth Wheatley (STScI)

Betelgeuse, Betelgeuse, Betelgeuse!

By Rae Redford Beyer Last updated Aug 12, 2022

The red supergiant Betelgeuse is as troublesome as Michael Keaton’s rambunctious spirit in the 1988 hit: Beetlejuice.

In 2019, Betelgeuse ejected a substantial amount of its surface into space in a Coronal Mass Ejection (CME) 400 billion times larger than anything from our sun. The distant star is still recovering.

A coronal mass ejection (CME) is a significant expulsion of plasma and magnetic field from a sun’s outermost atmosphere, or corona. Our sun can eject a billion tons of material at a speed of a million miles per hour (1.6 kilometers).

Astronomers discovered the CME while analyzing data from NASA’s Hubble Telescope and other observatories. Such observations can give us insight into the later lives of stars as their nuclear fusion diminishes, and they lose mass. Eventually, such stars explode into supernovae.

While astronomers don’t expect Betelgeuse to blow any time soon, astronomers have never seen such a titanic eruption.

Andrea Dupree, Center for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts, is taking a closer look at data from the star before, during, and after the expulsion.

“We’ve never before seen a huge mass ejection of the surface of a star. We are left with something going on that we don’t completely understand. It’s a totally new phenomenon that we can observe directly and resolve surface details with Hubble. We’re watching stellar evolution in real time,” Dupree said.

The fractured piece of Betelgeuse’s surface weighs several times more than our Moon. It cooled as it traveled through space, eventually becoming a dust cloud that blocked the star’s light—a phenomenon easily visible on Earth, even by backyard observers. The dimming lasted several months.