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Betelgeuse's Atmosphere Disturbed by Companion Star
Confirmed
In Short: New observations from the VLA and ALMA telescopes show Betelgeuse's outer atmosphere has rebounded and is being reshaped by its companion star.
Scientists using the VLA and ALMA telescopes have observed that Betelgeuse's outer atmosphere has rebounded, hinting at the influence of its companion star.
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 temperature of Betelgeuse's atmosphere, about 3,500 K at 22 GHz, now matches the star’s photospheric temperature.
Dr. Matthews noted, “The fact that we can use these facilities to actually resolve the disks of nearby stars is amazing.”
In 2019 and 2020, Betelgeuse underwent its most dramatic dimming in more than a century of records.
Betelgeuse is one of the most luminous stars known, emitting more light than 100,000 Suns, and has a radius around 1,400 times larger than the Sun’s.
Dr. Matthews explained, “It was the combination of the incredible data from the VLA and ALMA that gave us a convincing result here.”
The companion star, Siwarha, is creating a wake-like disruption in Betelgeuse’s outer atmosphere as it orbits directly through it.
Siwarha, a young yellow star not quite on the main sequence, is likely leaving a wake in its path as it rips through the atmosphere.
Betelgeuse is usually visible to most people around Earth from September through March, with the best views in December.
The star goes through a cycle of appearing more circular and more egg-shaped, suggesting a companion mass is distorting the star.
What this adds
The companion star Siwarha is reshaping Betelgeuse's atmosphere, creating a wake-like disruption.
The observations provide evidence for atmospheric perturbations from a close companion, confirming the star's companion's influence.
The star's variable patterns, including a 425-day cycle and a second pattern of about 5.9 years, suggest the companion's impact.
What's confirmed
- 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.
What's still developing
- Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA) show the red supergiant star’s outer atmosphere has rebounded and hint that its recently identified companion star is reshaping it.
- Let's start with the scientific characteristics of Betelgeuse.
- Distant celestial body : Betelgeuse is 650 light-years from us, which means that the light we see from Betelgeuse today began its journey in the Middle Ages.
- Look up at the evening on October 29 or before sunrise on October 30 to see the waning gibbous Moon form a large triangle with Aldebaran and Betelgeuse.
- The base, from Aldebaran to Betelgeuse, will stretch about 21.4°.
- In July 2025, astronomers reported the first probable direct detection of Betelgeuse’s long-suspected companion.
- Open the Star Walk 2 app, and it will guide you straight to it.
- From some locations, the Moon will appear equally far from both stars, creating an isosceles triangle.
- Betelgeuse probably won’t go supernova anytime soon — but that’s no reason to overlook it.
- 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.
- "New Spatially Resolved Observations of Betelgeuse from the VLA and ALMA: Evidence for Atmospheric Perturbations from a Close Companion."
- We can't observe this companion directly, so there has been some debate as to whether the companion truly exists.