File:Betelgeuse.jpg

English: Betelgeuse (Alpha Orionis), the reddish star at the shoulder of Orion, is a semiregular variable star, which usually shines at about magnitude +0.5, only slightly fainter than Rigel (Beta Orionis), the blueish star at the foot of Orion at maigitude +0.1.

In late 2019 and early 2020, however, Betelgeuse underwent an unusually deep minimum, when its magnitude dropped to about +1.6. That is, it shone at less than 40% of its usual luminosity, so its brightness was comparable to Bellatrix (Gamma Orionis), the other shoulder star (+1.6 mag).

In this view, the usual appearance of Orion (left, in an image taken on February 22, 2012), is compared with a image taken taken on February 21, 2020 (right), clearly showing the unusual dimming of the red giant star.

Both images were taken with identical setup and exposure data: Each is a 30-second exposure taken with a Canon EOS 550D camera at ISO 3200, 17mm f/2.8 lens, Cokin P830 diffuser, tracked with the Vixen Polarie star tracker.