For decades, scientists have suspected that Betelgeuse—the giant red star that forms Orion’s shoulder—wasn’t alone.
Now, a team from Carnegie Mellon University (CMU) has confirmed that this famous star has a small companion, affectionately nicknamed “Betelbuddy.”
The discovery came thanks to perfect timing and quick action.
Around December 6, the smaller star reached its widest visible separation from Betelgeuse before it would vanish behind it again for two years.
Realizing this rare opportunity, CMU researchers applied for emergency observation time on NASA’s Chandra X-ray Observatory and the Hubble Space Telescope. Getting both approvals for the same event is extremely rare and reserved for only the most promising scientific opportunities.
Dr. Anna O’Grady, a McWilliams Postdoctoral Fellow at CMU, explained that Betelgeuse’s extreme brightness has long made it nearly impossible to spot anything nearby.
“The brightness difference between Betelgeuse and this little companion is absolutely insane,” she said. “The fact that we can now confirm something is there shows how far our science has come.”
Images taken with the Gemini North Telescope in Hawaii revealed a faint glow beside Betelgeuse.
Chandra’s X-ray data helped the researchers determine what kind of object it was.
The team considered several possibilities—it might have been a dense, dead star such as a white dwarf or a neutron star.
But X-ray observations showed no signs of accretion, a process that would occur if Betelgeuse were feeding material onto such an object.
Instead, the results indicate that Betelbuddy is a small, young star about the size of our Sun. Additional data from Hubble supported this finding.
This discovery not only confirms the existence of a companion star but also challenges existing theories about how such mismatched pairs form.
Betelgeuse is about 16 or 17 times more massive than the Sun, while its companion is just one solar mass or less—a combination that astronomers rarely see.
The finding may also help explain Betelgeuse’s mysterious six-year pattern of brightening and dimming.
Earlier research suggested that a companion star could clear away dust around Betelgeuse, temporarily making it appear brighter from Earth. Now that Betelbuddy’s existence is confirmed, this explanation seems much more likely.
For O’Grady and her colleagues, the project began as a casual idea discussed during a research group meeting—but it quickly became one of the most exciting astronomical events of the year. As she put it, “It was awesome to see a casual conversation turn into a super exciting discovery opportunity.”
