Betelgeuse has a hidden companion — and it is quietly stirring the giant star's atmosphere

Betelgeuse, the bright red star on Orion's shoulder, has a houseguest. New radio observations from two powerful telescope arrays — the Very Large Array in New Mexico and ALMA in Chile — show the giant star's outer atmosphere has recovered from its famous dimming of 2019–20, when it faded to its faintest in a century. The same data reveal something subtler: a smaller companion star, named Siwarha — Arabic for “her bracelet” — is orbiting so close that it passes through Betelgeuse's own atmosphere, leaving a wake behind it, like a boat crossing a lake. Astronomers cannot see Siwarha directly at these wavelengths, but they can see the giant star stretch slightly egg-shaped when the companion swings widest, and round out again as it passes in front or behind — ripples that betray something moving just beneath the surface.