New Atacama Large Millimeter/submillimeter Array (ALMA) images of Betelgeuse reveal persistent hot spots, powerful convection and a distorted atmosphere around the famous red supergiant star.
This ALMA image shows the red supergiant star Betelgeuse. Image credits: ALMA / ESO / National Astronomical Observatory of Japan / NRAO / Dent et al..
Betelgeuse is an approximately 8-million-year-old red supergiant star located about 724 light-years from Earth in the constellation Orion.
With a radius roughly 1,400 times greater than the Sun’s, Betelgeuse is among the largest stars known to astronomers.
Also designated Alpha Orionis or Alpha Ori, Betelgeuse is one of the brightest stars in the night sky. It radiates more than 100,000 times the energy produced by the Sun.
Astronomers have long suspected that Betelgeuse has an uneven, patchy surface shaped by enormous convective cells—vast bubbles of hot gas rising from deep inside the star.
“Betelgeuse (HD 39801, α Ori) is one of the two closest red supergiant stars and, as a prototype, is the subject of intense study across radio, infrared, optical and X-ray wavelengths,” said ESO astronomer Bill Dent and his colleagues.
“The relatively large angular diameter of the photosphere makes it resolvable with current equipment.”
The research team observed Betelgeuse in August 2023 with the Atacama Large Millimeter/submillimeter Array, better known as ALMA.
The resulting images show that Betelgeuse’s photosphere—the optically thick layer of hot gas surrounding the visible surface—has an average temperature of approximately 2,300 K.
ALMA also detected two significantly hotter regions on the star, located to the northeast and southwest. The brightest region, in the northeast, is about 800 K hotter than the surrounding photosphere.
Notably, the position and brightness of the northeastern hot spot closely match observations made in 2015. This suggests that the feature has persisted for at least seven years.
The astronomers also identified a radial “waveform” extending up to approximately 6% of Betelgeuse’s apparent radius. The structure is concentrated in one sector of the star, although its detailed shape has changed considerably since 2015.
The researchers attribute these features to intense convection inside Betelgeuse. Rising cells of hot gas can disturb the star’s outer atmosphere, encouraging the formation of molecules such as silicon monoxide and carbon monoxide. These molecules can eventually contribute to dust formation and may help drive the loss of stellar material into interstellar space.
“It will be interesting to see what it actually looks like now, with its ultimate fate as a supernova,” Dr. Dent said.
“When Betelgeuse eventually explodes, it will be bright enough to be seen from Earth in broad daylight.”
The research results will be published in the journal Astronomy & Astrophysics.
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Dent WR et al.. 2026. High-resolution observations of Betelgeuse with ALMA: Persistent structures in the inner atmosphere. A&A, in press. arXiv:2608.19339
Source: www.sci.news