Hey, remember Betelgeuse? It caused quite a kerfuffle both among astronomers and normal people in late 2019 and early 2020 when the star's brightness dropped precipitously. There was much speculation in social media that it might explode, but astronomers knew this was incredibly unlikely. What they were more concerned with was why the star suddenly dimmed so dramatically: What was going on in the upper layers of this enormous star that could make such a huge difference in its light?
It seems pretty clear now that the red supergiant expelled an enormous cloud of dust, which blocks visible light, dimming it substantially. It's not clear why this happened and why on such a huge scale. Massive stars like Betelgeuse have complicated effects going on in their upper layers which can cause the star to physically pulsate, getting bigger and smaller over time. It's likely some other event happened in the star (perhaps a rising plume of hot gas) coupled with the normal pulsation, causing the creation of the dust that dimmed it.
A before-and-after set of images of Betelgeuse show how it’s changed from January 2019 (left) to December 2019 (right). Credit: ESO/M. Montargès et al.
This event, and the ...