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Something spooky is stirring in the shadows of the infamous star Betelgeuse, a cosmic poltergeist that is disrupting the atmosphere of the red supergiant.
New radio observations have shown Betelgeuse’s smaller stellar companion, Siwarha (not Betelguese Betelguese, unfortunately), cutting through the supergiant’s extended atmosphere and leaving a wake in its path, like a jet boat slicing through a lake.
Because the name of this red supergiant star located about 650 light-years away from Earth, marking the shoulder of constellation Orion, is Betelgeuse, which means “the hand of al-Jawza” in Arabic, the companion was named Siwarha, meaning “her bracelet.”
“This companion is orbiting so close to the star that it actually passes through its extended atmosphere,” Lynn Matthews, the principal research scientist at Massachusetts Institute of Technology (MIT) Haystack Observatory who led the new observations, said in a statement.
Astronomers turn cosmic ghost hunters
Using data collected from 2021 to 2026 using the Karl G. Jansky Very Large Array in New Mexico and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, Matthews and colleagues found that Betelgeuse’s atmosphere stretches into an egg shape when the companion star is farthest away and rounds out when the companion passes in front of or behind it.
The same data also showed that Betelgeuse itself has largely recovered from the “Great Dimming” that made headlines in 2020. This recovery comes after the red supergiant “sneezed” in 2020, dramatically ejecting tons of gas and dust and fading to its dimmest in more than a century.
Among the long-standing mysteries of Betelgeuse, scientists have puzzled over a brightening and dimming cycle that lasts roughly 2,100 days. Recent studies pointed to a low-mass companion orbiting deep inside the star’s atmosphere, and its existence was confirmed in early 2026.
Though Siwarha itself is too faint to detect directly at radio wavelengths, its influence shows up in the star’s shape, the new study found. To confirm the effect, the researchers say, they will need to observe more of the companion’s orbit, especially at radio frequencies that have so far been sparsely sampled.
The Next Generation Very Large Array, a planned telescope, should make this kind of monitoring far more routine, according to the team. With sharper vision, researchers could see how red supergiants like Betelgeuse shed their material as they near the end of their lives, and how a close companion might affect that process by tugging on that ejected matter.
This research is described in a paper published in The Astronomical Journal.
