New ALMA observations show that the red supergiant's inner atmosphere has become more patchy and asymmetric since 2015, with hot regions around it of about 800 degrees. The structure may be related to the direction of the companion star's orbit, but the connection is still unproven.
Beetlejuice, the famous red supergiant on the shoulder of the group Orion, continues to provide astronomers with surprises. New observations in the radio array ALMA They reveal that the star's inner atmosphere is not a smooth, uniform envelope, but a patchy, asymmetrical structure in which certain regions are hundreds of degrees hotter than their surroundings.
The study, led by William Dent and colleagues, was accepted for publication in Astronomy & Astrophysics and is the subject of the journal's DOI. The researchers used ALMA in its longest baseline configuration to image the region extending roughly from the photosphere to several times the radius of the star.
7ms resolution
ALMA operates at millimeter and submillimeter wavelengths. At these wavelengths, it is possible to observe hot, ionized layers just above the visible surface of Betelgeuse.
The researchers achieved a resolution of about 7 billion arcseconds. According to Dennett, if such a resolution were applied to the moon, it would allow for the detection of details about 13 meters in size.
The new observations were compared to previous ALMA measurements from 2015, that is, before the "great dimming" of Betelgeuse in 2019–2020.
The atmosphere became less symmetrical.
The most noticeable result is that Betelgeuse now looks more spotty and asymmetrical.
The continuous emission indicates a submillimeter "photosphere" layer with a radius of about 1.1–1.3 times the radius of the star, with a typical temperature of about 2,300 Kelvin. Above this background, two particularly hot regions appear in the northeast and southwest.
The most prominent of these is about 800 Kelvin hotter than its surroundings.
Even more surprising: the brightest hot spot appears in roughly the same place as it was already seen in the 2015 observations. The researchers expected that the cells transportation Supernovae in such a star will evolve and change, but it seems that at least some of the structure has been preserved for longer than the models predict.
Star-scale convection chambers
In the sun, many convection cells transfer heat from the inner layers outward. Hot gas rises, cools, and sinks back down.
A red giant like Betelgeuse is on a completely different scale. Instead of a huge number of relatively small cells, there may be a small number of giant convection cells operating, each of which covers a significant portion of the star's surface.
ALMA also detected fragmented emission of molecules such as SiO and CO outside the submillimeter photosphere. Such structures may be related to shocks and gas flows originating in the convection cells.
Understanding the process is important because red supergiants lose large amounts of material into space. This material subsequently enriches the interstellar medium, from which new generations of stars and planetary systems are formed.
And what about the companion star?
In recent years, evidence has grown that beetlejuice has Companion star Smaller in a close orbit. In 2025, a direct observation of the companion star was even announced using the Gemini Observatory.
In the current study, the researchers observed that the hot spots show a preference for a particular direction.
If the companion's orbit is aligned with Betelgeuse's equatorial plane, the bright spots may be near the star's polar regions, where convection is more stable or active.
But this is still a hypothesis.
The study does not prove that the companion star creates the spots, nor does it prove that its orbital plane actually aligns with Betelgeuse's equator. The researchers themselves emphasize that further observations are needed to test the connection.
There is no sign that a supernova is about to happen now.
Any change in Betelgeuse immediately raises the question of whether the star is about to explode.
The new observations do not provide evidence that a supernova explosion is imminent in human time. They deal with the structure of the outer atmosphere and convection, not with the processes in the core that dictate the timing of the supernova.
The great dimming of 2019–2020 sparked a similar wave of speculation, but the event was later found to be mainly related to the ejection of material and the creation of dust that blocked some of the star's light.
A laboratory close to the life of massive stars
Betelgeuse is relatively close to Earth and therefore allows us to study in detail processes that in other supergiants are only visible as a combined light signal from a single point.
The picture that is now emerging is not of a smooth red ball, but of a massive, active, spotty, and variable star, from which material flows into space in a process that astronomers still do not fully understand.
Precisely because it is so close, Betelgeuse allows us to see what the final stage of a massive star's life actually looks like – long before the moment of explosion itself.
Questions and Answers
What did ALMA discover in Betelgeuse? A patchy and asymmetrical inner atmosphere with hot regions, one of which is about 800 Kelvin hotter than its surroundings and is seen in a location similar to the one observed in 2015.
Does the companion star cause spots? There may be a geometric relationship between the location of the spots and the proposed trajectory of the companion, but the study does not prove causality.
Does this mean that Betelgeuse is about to explode? No. The study is about the atmosphere and convection. It has no indication that a supernova is about to occur soon.
Why is Betelgeuse's atmosphere important? Because through it, the star loses material that enriches the interstellar medium, and the process of losing mass is a central stage in the development of massive stars towards the end of their lives.
The scientific article
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More on the subject on the science website
- After decades of searching: Betelgeuse's elusive companion star discovered
- New evidence that the nearby red giant Betelgeuse has a companion hidden from our eyes
- The famous star Betelgeuse has faded, but it still probably won't explode anytime soon
- Beetlejuice: The star continues to behave mysteriously - here's what will happen if it explodes
- Impending explosion: Massive stars alert when they're about to go supernova
One response
Why not call it by its Hebrew/Arabic name - Beit Egoza, whose English name is simply a distortion of it.