Digital painting of the red giant star Betelgeuse and its newly discovered companion Siwarha. Simulations suggest giant stars have a small number of enormous convection cells rather than a huge amount of continent-sized convection cells as on the Sun, and that their photospheres are not a hard boundary but rather smoothly deform into a corona.
Betelgeuse is 640 times the size of the Sun (or 2.98 au radius). It is 65,000 times more luminous than the Sun. But as opposed to the Sun's 5800 K surface temperature, Betelgeuse is only 3800 Kelvins, leading to an almost candle-like yellow-orange glow.
Siwarha is depicted here as a K-dwarf, 2/3rds the mass of the Sun. It is thought to be responsible for a 6-year-long periodic change in Betelgeuse's apparent brightness--It casts a wake behind it as it travels through Betelgeuse's nebulous and dusty corona.
