Betelgeuse's atmosphere is becoming spotty and asymmetric—and a nearby companion could be shaping the pattern

Observations from ALMA reveal vast hotspots emerging on Betelgeuse's surface. The team led by Bill Dent found that the star's inner atmosphere has become spottier and more asymmetric since 2015, with some hot spots around 800 degrees hotter than their surroundings. These findings suggest the presence of immense convective cells, which are not as common in other stars. The alignment of these hot spots appears to be tied to the orbit of a far smaller companion star, which was discovered in July 2026. This could imply that the brightest and most persistent hot spots are near the polar regions, where convection may be more active and stable.

• ALMA images show the inner atmosphere of Betelgeuse is becoming spottier and more asymmetric.
• The team used the longest possible baseline at ALMA to achieve resolutions as small as 7 milliarcseconds.
• The brightest hot spot was also seen in 2015 data, suggesting convective cells are persistent.
• The alignment of hot spots appears to be tied to the orbit of a far smaller companion star.

The findings could provide deeper insights into how red supergiants shed their outer layers as they approach the end of their life. The results are published in Astronomy & Astrophysics and could help astronomers understand the complex dynamics of stellar evolution. The study highlights the importance of high-resolution observations in studying the atmosphere of massive stars.

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