Betelgeuse Has a Lydia Too: Hubble Just Discovered the Red Supergiant's Secret Companion Star

EARTH, Laniakea Supercluster—You don’t have to say it three times for it to appear.

Betelgeuse, the red supergiant on Orion’s shoulder, is one of the night sky’s brightest stars regularly visible from much of Earth. But something was hiding.

Astronomers recently discovered that Betelgeuse was long shadowed by its own hidden Lydia-esque star, although hopefully it wasn’t kidnapped like Winona Ryder in the Hollywood films.

The clue was a trail of gas that kept showing up every six years—dense, swirling, and completely unexplained. For nearly a decade, astronomers watched it ripple through the outer atmosphere of one of the most famous stars in the sky and couldn’t figure out what was causing it.

Using nearly eight years of observations from Nasa’s Hubble Space Telescope and ground-based observatories, Scientists at Harvard’s Center for Astrophysics recently confirmed the existence of a small companion star and named it Siwarha, or ”Her bracelet” in Arabic—a fitting companion to Betelgeuse, whose name derives from the Arabic for “Hand of the Giant.”

And Siwarha isn’t just orbiting calmly. It’s moving through Betelgeuse’s gas like a dancer swirling through mist, leaving a rippling and turbulent trail that alters what astronomers detect from more than 650 light-years away.

“It’s a bit like a boat moving through water,” Dupree said a team led by Andrea Dupree at the Center for Astrophysics. “The companion star creates a ripple effect in Betelgeuse’s atmosphere that we can actually see in the data.”

The discovery, presented at the 247th meeting of the American Astronomical Society and accepted for publication in The Astrophysical Journal, resolves one of the longest-running mysteries in stellar astronomy: why Betelgeuse’s brightness shifts on a strange 2,100-day cycle.

Every six years, Siwarha crosses between Betelgeuse and Earth, and its wake—a trail of material denser than the surrounding atmosphere—disrupts the star’s spectrum of light. That cycle had baffled scientists for years, with explanations ranging from giant convection cells to magnetic storms to clouds of dust.

Turns out it was just a little star with a big wake.

To grasp the scale: Betelgeuse is a red supergiant roughly 1,400 times the diameter of our Sun. If you dropped it into our solar system, its surface would swallow everything out to Jupiter. Siwarha, by contrast, may be smaller than the Sun. “So the companion is really plowing through a dense atmosphere of the supergiant star,” Dupree said.

The find also reframes Betelgeuse’s infamous 2020 “Great Dimming,” when the star appeared to sneeze out a dust cloud and temporarily faded from view. Astronomers now understand that Siwarha’s gravitational churning likely plays a role in how Betelgeuse sheds material—a process that will ultimately end when the supergiant detonates as a supernova.

“With this new direct evidence, Betelgeuse gives us a front-row seat to watch how a giant star changes over time,” Dupree said. “Finding the wake from its companion means we can now understand how stars like this evolve, shed material, and eventually explode.”

Nobody knows exactly when Betelgeuse will blow. But now they know it won’t go alone.