Betelgeuse's Hot Spot Has Stayed in the Same Place for Over 7 Years; Average Surface Temperature Is 2,300 K (ALMA)

Explanation

On August 24, 2026, the Atacama Large Millimeter/submillimeter Array (ALMA), a radio interferometer operated by the European Southern Observatory (ESO), the National Astronomical Observatory of Japan (NAOJ), and others, announced observation results capturing the surface of Betelgeuse, the red supergiant in Orion, at the highest resolution ever achieved.

Betelgeuse is located "about 600 light-years" from Earth, and its radius reaches "about 800 times" that of the Sun. Thanks to this enormous size, ALMA, using its longest baseline, was able to resolve surface structure at a fineness of "about 7 milliarcseconds." According to the observations, the average temperature of the atmosphere was "about 2,300 K," and hot spots existed to the northeast and southwest of the star that were up to "about 800 K" hotter than their surroundings.

When the research team compared observations from 2023 and 2015, the brightest hot spot, located to the northeast, appeared in almost the same position with almost the same brightness. This indicates that the hot spot has persisted for "at least 7 years," suggesting it may be surviving far longer than current convection models predict.