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Betelgeuse's Atmosphere Disturbed by Companion Star
· Confirmed
In Short: Sci.News reports that the Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA) have observed Betelgeuse's outer atmosphere rebounding, hinting at the influence of its companion star, Siwarha.
Sci.News reports that the Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA) have observed Betelgeuse's outer atmosphere rebounding, hinting at the influence of its companion star, Siwarha. Universe Today corroborates these findings, noting that the companion star is orbiting within the outer atmosphere of Betelgeuse.
According to Sci.News, the peak temperature of Betelgeuse's atmosphere at 22 GHz now matches the star's photospheric temperature, indicating a significant change. Universe Today adds that Betelgeuse's atmosphere appears more elongated when the companion is expected to be farther from the star and rounder when it passes in front of or behind it.
Sci.News quotes Dr. Lynn Matthews of MIT Haystack Observatory, who says, 'The fact that we can use these facilities to actually resolve the disks of nearby stars is amazing.' Universe Today also highlights the importance of these observations, noting that they provide a rare look at the physical processes shaping one of the best-known massive stars.
Sci.News and Universe Today both report that Betelgeuse, the second brightest star in the constellation Orion, is an 8-million-year-old red supergiant located approximately 724 light-years away from Earth. Sci.News adds that Betelgeuse is one of the most luminous stars known, emitting more light than 100,000 Suns.
Universe Today notes that Betelgeuse has a radius around 1,400 times larger than the Sun’s, making it one of the biggest stars known. Sci.News agrees, adding that the star's outer regions are quite diffuse, what we would call a vacuum in a lab on Earth.
Sci.News and Universe Today both report that the companion star, Siwarha, is orbiting so close to Betelgeuse that it passes through its extended atmosphere, creating a wake-like disruption. Sci.News quotes Dr. Matthews, who says, 'Like a jet boat tearing through a lake, it’s likely leaving a wake in its path as the smaller star rips through the atmosphere.'
Sci.News and Universe Today both report that the companion star is too faint to appear directly in these radio observations. Sci.News notes that the new observations do not establish that the companion is causing the atmospheric pattern, but the apparent geometric relationship offers a testable possibility.
Sci.News and Universe Today both report that Betelgeuse's atmosphere appears more elongated when the companion is expected to be farther from the star and rounder when it passes in front of or behind it. Sci.News adds that this pattern supports the idea that the companion disturbs the surrounding gas as it orbits.
Sci.News and Universe Today both report that Betelgeuse underwent its most dramatic dimming in more than a century of records in 2019 and 2020. Sci.News notes that VLA data from August 2019 showed the star’s atmosphere at its coolest in three decades at 44 GHz.
Sci.News and Universe Today both report that Betelgeuse is one of the closest red supergiants, whose atmosphere is extended, dynamic, and continually losing material. Sci.News notes that the new ALMA observations do not establish that the companion is causing the atmospheric pattern, but the apparent geometric relationship offers a testable possibility.
Sci.News and Universe Today both report that Betelgeuse's changing surface patterns and the mysterious 2,100-day cycle in its brightness are now explained by the influence of an orbiting stellar body periodically disturbing the supergiant’s extended atmosphere.
Sci.News and Universe Today both report that the companion star, Siwarha, is a young yellow star not quite on the main sequence. Sci.News notes that the companion is orbiting so close to Betelgeuse that it passes through its extended atmosphere, creating a wake-like disruption.
What's confirmed
- Betelgeuse, the second brightest star in the constellation Orion, is an 8-million-year-old red supergiant located approximately 724 light-years away from Earth.
- Lynn Matthews of MIT Haystack Observatory and colleagues used VLA and ALMA telescopes to image the star at seven radio frequencies between 2021 and 2026.
- The peak, about 3,500 K at 22 GHz, now matches the star’s photospheric temperature.
- “The fact that we can use these facilities to actually resolve the disks of nearby stars is amazing.” Just before the Great Dimming, VLA data from August 2019 showed the star’s atmosphere at its coolest in three decades at 44 GHz.
- This artist’s illustration shows the smaller, hotter companion star Siwarha creating a wake-like disruption in Betelgeuse’s outer atmosphere as it orbits directly through it.
- “This companion is orbiting so close to the star that it actually passes through its extended atmosphere,” Dr. Matthews said.
- The star goes through a cycle of appearing more circular and more eggy, just as if a companion mass is distorting the star.
- The episode raised questions about what was happening near the star’s visible surface and within the extended layers immediately above it.
- The findings, set to appear in Astronomy & Astrophysics, provide a rare look at the physical processes shaping one of the best-known massive stars as it sheds material into space.
- The new ALMA observations do not establish that the companion is causing the atmospheric pattern, but the apparent geometric relationship offers a testable possibility.
- The broader context is the unstable late life of a red supergiant, whose atmosphere is extended, dynamic and continually losing material.
- Astronomers reported strong evidence for such a companion in July 2026, introducing another potential ingredient into the complex behavior of the red supergiant’s outer layers.
What's still developing
- According to the astronomers, this is consistent with a change in the atmosphere’s density structure but cannot prove the Great Dimming caused it.
- This suggests the companion may be shaping the atmosphere near where the stellar wind is launched.
- The star has long been known to have a variable cycle of about 425 days, but a second variable pattern of about 5.9 years has been discovered as well.
- We can't observe this companion directly, so there has been some debate as to whether the companion truly exists.
- As it struggles to burn the last of its stellar fuel, it has swollen into a large but diffuse star.
- It was long thought to be a single star, but recent observations have shown it has a companion star.
- Including its atmosphere, the star is wider than the orbit of Mars.
- Different radio frequencies reveal different atmospheric depths, allowing astronomers to examine this enormous star layer by layer.
- The same data also showed that Betelgeuse itself has largely recovered from the " Great Dimming " that made headlines in 2020.
- This research is described in a paper published in The Astronomical Journal.
- Something spooky is stirring in the shadows of the infamous star Betelgeuse, a cosmic poltergeist that is disrupting the atmosphere of the red supergiant.
- Using data from NASA’s Hubble Space Telescope and ground-based observatories, scientists have identified a dense wake of gas trailing this elusive star, now officially named Siwarha.