Analyzing data from NASA's Hubble Space Telescope and several other observatories, astronomers have concluded that the red supergiant star Betelgeuse lost a substantial part of its visible surface in an event known as a Surface Mass Ejection (SME) in 2019. This is something never before seen in a normal star's behavior.

Our Sun routinely blows off parts of its tenuous outer atmosphere, the corona, in an event known as a Coronal Mass Ejection (CME). But the Betelgeuse SME blasted off 400 billion times as much mass as a typical CME! The star is still slowly recovering from this catastrophic upheaval.

These new observations yield clues as to how red stars lose mass late in their lives as their nuclear fusion furnaces burn out, before exploding as supernovae.