On a clear night in December, astronomers at the Gemini North telescope in Hawai‘i turned their focus to Betelgeuse, a bright red star in Orion that has dazzled both astronomers and the public for generations. The star’s regular dimming every six years hinted at the presence of a hidden companion — a possibility that had remained unconfirmed for over a century. Now, researchers have finally spotted the faint star orbiting nearby.
The findings confirm a long-standing theory first proposed in the early 1900s. More importantly, it sheds new light on how massive stars evolve and die, as well as how their close companions might shape that process. The newly discovered companion has been named Siwarha, an Arabic word meaning “her bracelet.”
An Old Hypothesis, A New Era
Astronomers have watched Betelgeuse for a long, long time. Across the years, they’ve built a rich catalog of its erratic changes in brightness and radial velocity — how it moves toward and away from Earth. Those variations hinted at gravitational nudges from a hidden partner. But Betelgeuse is enormous, more than 700 times the size of the Sun, and glows so fiercely that any faint companion would be overwhelmed in its light.
Despite repeated efforts using space telescopes like Hubble and Chandra, Siwarha eluded detection. But in 2024, two new studies — including one led by Morgan MacLeod of the Harvard-Smithsonian Center for Astrophysics — reexamined over a century of observations and noticed something striking: a consistent six-year signal in Betelgeuse’s brightness and radial motion. That pattern, they argued, was best explained by a small, unseen star in a tight orbit.
Their models predicted exactly where the companion should appear — and that December 2024 would be the brief window when it would be far enough from Betelgeuse to be seen.
That’s when Howell and his team seized the opportunity.
Using the ‘Alopeke (“fox” in Hawaiian) speckle imager on Gemini North, they captured thousands of rapid-fire exposures. This technique, called speckle imaging, corrects for the blurring effects of Earth’s atmosphere and creates images with stunning sharpness.
When the data were processed, a faint blue-white point of light emerged. Siwarha had finally been spotted.
A Ghostly Star in a Deadly Dance
Siwarha is about 1.5 times the mass of our Sun and likely hasn’t even started fusing hydrogen in its core — the defining trait of a “main sequence” star like the Sun. Betelgeuse, by contrast, is racing toward its end. Though only about 10 million years old, its massive size has caused it to burn through its nuclear fuel rapidly.
“You have a star that is about to die, and it’s being orbited by a star that’s not fully born,” Miguel Montargès, an astronomer at the Paris Observatory who was not involved in the discovery, told New York Times.
The two stars are so close that Siwarha’s orbit takes it through the puffed-up outer layers of Betelgeuse’s atmosphere. It is, in effect, wading through stellar molasses. This orbital ballet explains Betelgeuse’s rhythmic dimming as well as its unexpectedly fast rotation, which may be the result of tidal spin-orbit interactions with the companion.
And it won’t last.
Models suggest Betelgeuse’s gravity will eventually drag Siwarha inward, swallowing it whole within the next 10,000 years. If Betelgeuse goes supernova before then (a very real possibility), its companion could be obliterated in the explosion. In either case, Siwarha’s fate is sealed.
“Betelgeuse and its buddy will hug eternally,” said Jared Goldberg, an astrophysicist at the Flatiron Institute. But I don’t think he meant it in a good way.
The Companion That Changed Everything
The idea that Betelgeuse might be a binary system isn’t new. In fact, astronomers in the early 1900s proposed it as a “spectroscopic binary” based on shifts in the star’s spectral lines. But its wild surface behavior — enormous convection cells, pulsations every 400 days, and a history of random “burps” of gas — made it hard to isolate a steady signal.
Then came the Great Dimming of 2019–2020. For a few months, Betelgeuse dropped dramatically in brightness, prompting rumors it might be about to go supernova. That wasn’t the case (the star blew out a cloud of dust that merely obscured it), but the event sparked a renaissance in Betelgeuse studies.
That renewed interest led MacLeod’s team to dig deeper into archival data. In their study, they modeled Betelgeuse’s movement using 128 years of radial velocity and brightness measurements. What emerged was a regular, six-year cycle — what they call the “long secondary period” or LSP.
Their statistical model pointed to a small companion in a 2,110-day (5.78-year) orbit, just over twice the radius of Betelgeuse — so close that it had been hiding in plain sight. The data suggested that the companion had a mass less than the Sun and was a million times fainter than Betelgeuse. Tellingly, the orbital plane aligns with Betelgeuse’s spin axis. This is likely because tidal interactions over thousands of years forced them into sync.
A System Out of Time
Betelgeuse and Siwarha were born together, likely from the same cloud of gas. But because of the quirks of stellar evolution, Betelgeuse raced ahead, growing large and unstable while Siwarha lagged behind. In the words of Howell, “It’s starting to become a real star, but unfortunately it’ll never make it.”
Betelgeuse’s enormous gravity is already disrupting Siwarha’s path, and the younger star may never get the chance to fully ignite. Either Betelgeuse will engulf it, or the shockwave from Betelgeuse’s eventual explosion will destroy it.
In the meantime, astronomers will have another chance to observe Siwarha in November 2027, when it again reaches its furthest point from Betelgeuse’s glare. That window may offer clearer views and more precise measurements of the doomed companion.
But even now, this discovery reshapes how scientists think about red supergiants. Many such stars show similar long-period variability, and the Betelgeuse–Siwarha system offers a compelling template. Perhaps, Howell suggested, more dying giants are concealing small, close-knit companions in their radiant shrouds.
As Betelgeuse inches toward its explosive finale, it does so with a partner in tow.
The findings appeared in The Astrophysical Journal Letters.
