The smoking gun (in a sense, literally) may have been found for the reason why Betelgeuse, everybody's favorite red supergiant star, dimmed so dramatically earlier this year: Dust. A lot of it.
Since 2020 has already been like 75 years along, here's a refresher: Betelgeuse is one of the brightest stars in the sky, located in the constellation of Orion (his right armpit; the name literally means "The Armpit of Orion" or "The Armpit of the Giant"). It's a red supergiant, a colossal star with 15 times the Sun's mass and a diameter of a staggering billion kilometers or more.
It undergoes regular variations in light, brightening and dimming over time. There are a couple of cycles on top of one another; one takes about 420 days (plus or minus), and the other about 2000 days. These variations usually change its brightness by a small amount; you'd really have to pay attention to notice under normal circumstances.
But in late 2019 Betelgeuse took a nosedive, and by mid February 2020 its brightness had dropped by a stunning 70%, so obvious you could just go outside and see it.
Cropped part of the full-resolution image of Betelgeuse shows countless stars as ...