Astronomers now think that unusually large dark starspots on the face of the red supergiant star Betelgeuse caused its dimming from October 2019 to April 2020.
“Corresponding high-resolution images of Betelgeuse from December 2019 show areas of varying brightness. Together with our result, this is a clear indication of huge star spots covering between 50% and 70% of the visible surface and having a lower temperature than the brighter photosphere,” said co-author Peter Scicluna from the European Southern Observatory (Eso).
“For comparison, a typical sunspot is the size of the Earth. The Betelgeuse star spot would be a hundred times larger than the Sun. The sudden fading of Betelgeuse does not mean it is going supernova. It is a supergiant star growing a super-sized star spot.” said co-author Prof Albert Zijlstra from The University of Manchester, UK
Starspots have been identified on the surface of Betelgeuse previously, so what is interesting here is how large these spots were.