Monster star had never-before-seen titanic eruption
11 Aug 2022



Astronomers using Hubble and other telescopes have found that supergiant star Betelgeuse blew off a huge piece of its visible surface in 2019. This has never before been seen on a star.

This plots changes in the brightness of Betelgeuse, following the titanic mass ejection of a large piece of its visible surface.

​​​​This plots changes in the brightness of 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.​​​

Credit: NASA, ESA, Elizabeth Wheatley (STScI)

​Betelgeuse appears as a brilliant, ruby-red, twinkling spot of light in the constellation Orion, which astronomers have been watching closely through the final stages of its life cycle.

Gigantic surface mass ejection

Our Sun routinely goes through mass ejections of its outer atmosphere, the corona, known as Coronal Mass Ejections (CMEs). But those events are orders of magnitude weaker than what was seen on Betelgeuse.

The first clue came when the star mysteriously darkened in late 2019. An immense cloud of obscuring dust formed from the ejected surface as it cooled. Astronomers have now pieced together a scenario for the upheaval. And the star is still slowly recovering; the photosphere is rebuilding itself. And the interior is reverberating like a bell that has been hit with a sledgehammer, disrupting the star's normal cycle. This doesn't mean the monster star is going to explode any time soon, but the late-life convulsions may continue to amaze astronomers.

Astronomers have concluded that the bright red supergiant star Betelgeuse quite literally blew its top in 2019. It lost a substantial part of its visible surface and produced a gigantic Surface Mass Ejection (SME), ejecting 400 billion times as much mass as a typical CME. This is something never before seen in a normal star's behavior.

Keeping an eye on Betelgeuse

The new data includes observations from a number of ground based and space based telescopes, including Hubble and, crucially, the Solar Terrestrial Relatio​ns Observatory (STEREO-A). A RAL Space-led instrument onboard STEREO-A has been stepping in to help provide a better view of the star during periods where it is too close to the Sun to be seen by the astronomy telescopes.

Professor Richard Harrison, RAL Space Chief Scientist and Principal Investigator for the Heliospheric Imager on STEREO-A said:

“Whilst Betelgeuse is being monitored from ground-based observatories, there are times when this is not possible due to the vicinity of the Sun, but the RAL Space-led Heliospheric Imager on the NASA STEREO-A spacecraft is uniquely suited to monitor its intensity at these times. We are really excited that a RAL Space instrument that is used to identify and track solar-ejected clouds has come to the rescue and is being used to keep an eye on Betelgeuse in this way."

​RAL Space scientists have contributed to the recent paper on Betelgeuse and the Heliospheric Imager will continue to watch as astronomers discover more as the star continues to build towards its supernova. 

Further information: