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New images of the star Betelgeuse taken by ALMA reveal hot regions, irregular surface, and a structure that may have remained stable for at least seven years.
A hot structure observed on Betelgeuse may have stayed nearly in the same place for at least seven years, contradicting the behavior predicted by models used by astronomers. This detail emerged when images obtained by the ALMA radio telescope in 2023 were compared to observations made by the same array in 2015.
The new images, released by the Atacama Large Millimeter/submillimeter Array (ALMA) of the European Southern Observatory (ESO), provide a clearer view of the supergiant’s surface. In addition to identifying regions with varying temperatures, the recordings show an irregular, dynamic atmosphere extending well beyond the visible part of the star.
One of the regions is 530 °C warmer than the surroundings
ALMA identified two particularly hot areas in Betelgeuse, located in the northeast and southwest regions. The most significant temperature difference reaches approximately 530 °C compared to the surrounding gas.
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The temperature of the star is estimated to be around 2,030 °C. The differences observed on its outer surface may be related to the circulation of material in the inner layers, where hotter gases advance toward the atmosphere.
This movement helps explain why the surface does not behave like a uniform structure. Instead, large areas of gas display distinct properties, creating the bubbling appearance observed by the instruments.
Structure has remained virtually in the same spot since 2015
The comparison between different time periods makes one of the hot areas even more interesting. A structure recorded in 2023 appears almost in the same region where ALMA had observed a similar formation in 2015.
This suggests a permanence of at least seven years, a period considered significant in light of the models used to explain the behavior of these large structures. According to existing predictions, formations of this nature should undergo transformations or disappear in a shorter time frame.
The discovery opens avenues for new investigations regarding the internal workings of Betelgeuse. Future observations may indicate whether the region will remain recognizable or if it will finally undergo deeper changes.
Betelgeuse does not have a perfectly round shape
Another result from the recordings is related to the supergiant’s appearance itself. The measurements indicate that the apparent size of Betelgeuse varies depending on the observed region, dispelling the notion of a perfectly spherical and regular surface.
The gas also significantly exceeds the boundaries of the visible part of the star, forming an extensive atmosphere. By analyzing observations over the years, researchers noted that certain regions changed more dramatically than others.
This combination indicates that different parts of the atmosphere can evolve at distinct rates. While one hot formation remained relatively stable, other structures exhibited noticeable changes between 2015 and 2023.
Supergiant Has Nearly 20 Times the Mass of the Sun
These dimensions help explain why Betelgeuse garners so much interest. The supergiant has a mass nearly 20 times greater than that of the Sun and has reached sizes equivalent to approximately 800 times that of our star.
Betelgeuse is also at an advanced stage of its evolution. Thus, monitoring the movement of gases and atmospheric transformations can assist astronomers in better understanding how red supergiants lose mass to space over their lifetimes.
The star is located approximately 600 light-years from Earth. Even at this distance, advancements in observational instruments allow for an investigation of its structure with a level of detail that was unavailable in the early decades of study.
First Direct Image Was Captured by Hubble in 1995
Visual interest in Betelgeuse did not start with ALMA. In 1995, the Hubble Space Telescope produced the first direct image of a star other than the Sun, specifically targeting this supergiant.
Decades later, the recordings made by ALMA in 2023 expanded the ability to study specific regions of its surface. The results allow for comparisons of temperatures, locations of structures, and changes that occurred over intervals of several years.
This continuity is particularly important because a single photograph captures only a moment. By contrasting different periods, astronomers can observe which elements of the star remain the same and which undergo transformations.
Images May Help Reassess Models of Giant Stars
The unexpected persistence of the hot region raises a critical question for current models: what processes can maintain a structure of this scale for such extended periods?
Answering this question could deepen understanding of gas circulation and energy transport in red supergiants. The observed behavior may also aid in comprehending how internal changes reach the outer layers and affect the atmosphere.
The next step will be to continue monitoring the star. If the hot area persists in future observations, astronomers will have an even longer period to explain it; if it disappears, it will be possible to document the conclusion of one of the most durable structures identified on its surface.
