Japanese weather satellite accidentally watched Betelgeuse go dim
Enlarge / These images, taken with the SPHERE instrument on ESO's Very Large Telescope, show the surface of the red supergiant star Betelgeuse during its unprecedented dimming. The image on the far left, taken in January 2019, shows the star at its normal brightness. The remaining images, from December 2019, January 2020, and March 2020 were all taken when the star's brightness had noticeably dropped. (credit: ESO/M. Montargès et al.)
Over the last couple of years, Ars has dedicated a fair number of electrons to our local red supergiant, Betelgeuse. The massive star went through an odd uneven dimming, leaving the astronomy community scrambling for explanations and observation time. While a degree of consensus slowly emerged, the lack of some key details left a lot unexplained.
It turns out that some of the answers were accidentally captured by an Earth-facing Japanese weather satellite that had Betelgeuse in-frame across the entire process of its dimming.
In the archives
In the new paper describing the results, Daisuke Taniguchi, Kazuya Yamazaki, and Shinsuke Uno say the astronomy community has settled on two options for explaining why a giant star like Betelgeuse might get dimmer. One is that internal processes could lower the star's effective temperature and thus its light output. The other option is that dust ends up between the star and Earth, absorbing some of the star's light. But both of those explanations are short on details; we don't really know what's happening inside the star or how enough dust could end up between Betelgeuse and Earth.