Betelgeuse will one day explode, and it's been acting strange recently. Astronomers have finally worked out what it is | BBC Sky at Night Magazine

Astronomers have confirmed the existence of a companion star, Siwarha, orbiting Betelgeuse, the red supergiant star in the constellation Orion. This companion star is causing periodic dimming of Betelgeuse by creating a wake of gas in its atmosphere. The discovery was made using the Hubble Space Telescope and ground-based observatories, and it helps explain Betelgeuse's long-standing mystery of its variability. The companion star's influence is evident in the changes in Betelgeuse's spectrum and the speed and direction of gas in its outer atmosphere. This discovery provides a unique opportunity to study how massive stars evolve and eventually explode as supernovae.