A pink supergiant star has blown an infinite bubble of gasoline and dirt, baffling astronomers.
The construction, as huge because the Solar and bigger than our photo voltaic system, fashioned in a sudden eruption hundreds of years in the past. Why the star didn’t explode as a supernova stays a thriller.
Discovery of a Huge Stellar Bubble
Astronomers at Chalmers University of Technology in Sweden have identified a gigantic, expanding bubble of gas and dust surrounding a red supergiant star. It is the largest structure of this kind ever observed in the Milky Way. Containing as much mass as the Sun, the bubble was expelled in a violent stellar eruption about 4000 years ago. Scientists are still puzzled as to how the star managed to survive such a dramatic event.
The findings, published in the journal Astronomy and Astrophysics, come from a team led by Mark Siebert of Chalmers. Using the ALMA radio telescope in Chile, the researchers studied the red supergiant known as DFK 52, a star similar in many ways to the famous Betelgeuse.
A Giant, Expanding Cloud of Gas and Dust
“We got a big surprise when we saw what ALMA was showing us. The star is more or less a twin of Betelgeuse, but it’s surrounded by a vast, messy bubble of material,” says Mark Siebert at Chalmers.
This immense cloud, made of gas and dust, holds as much mass as the Sun and stretches 1.4 light years from the star. To put that in perspective, the bubble is thousands of times wider than our entire solar system.
If DFK 52 were as close to Earth as Betelgeuse, the bubble would appear to cover about one third of the full Moon’s width in the night sky.
By tracking the movement of molecules in the gas with ALMA’s radio observations, astronomers determined that the bubble is still expanding. They believe it originated when the star violently ejected part of its outer layers during an explosive outburst a few thousand years ago.
“The bubble is made of material that used to be part of the star. It must have been ejected in a dramatic event, an explosion, that happened about four thousand years ago. In cosmic terms, that’s just a moment ago,” says Elvire De Beck, astronomer at Chalmers.
The Galaxy’s Next Supernova?
Why DFK 52 shed so much mass without exploding as a supernova is still unclear. One possibility is that the star has a hidden companion that helped it cast off its outer layers.
“To us, it’s a mystery as to how the star managed to expel so much material in such a short timeframe. Maybe, like Betelgeuse seems to, it has a companion star that’s still to be discovered,” says Mark Siebert.
Red supergiants like DFK 52 are nearing the ends of their lives and are expected to eventually explode as supernovae. Could this star be next?
“We’re planning more observations to understand what’s happening – and to find out whether this might be the Milky Way’s next supernova. If this is a typical red supergiant, it could explode sometime in the next million years,” says Elvire De Beck.
Reference: “Stephenson 2 DFK 52: Discovery of an exotic red supergiant in the massive stellar cluster RSGC2” by M. A. Siebert, E. De Beck, G. Quintana-Lacaci and W. H. T. Vlemmings, 6 August 2025, Astronomy & Astrophysics.
DOI: 10.1051/0004-6361/202555975
The study was carried out by Mark Siebert, Elvire De Beck, and Wouter Vlemmings from Chalmers University of Technology in Sweden, together with Guillermo Quintana Lacaci from the Instituto de Fisica Fundamental in Spain.
Red supergiants are among the brightest and rarest stars visible in the universe. They represent the final stage in the lives of stars that began with far greater mass than our Sun (more than eight times its mass). For astronomers, these stars are crucial for piecing together the life cycles of stars and planets. The most massive ones produce and release newly created elements into interstellar space, stirring up gas and dust and fueling the formation of future generations of stars.
Within our own galaxy, the Milky Way, some red supergiants are visible without a telescope to anyone under a dark sky. Two of the best-known examples are Betelgeuse in the constellation Orion and Antares in Scorpius.
The Atacama Large Millimeter/submillimeter Array (ALMA) is a world-class observatory located in Chile. It is operated as a collaboration between ESO, the U.S. National Science Foundation (NSF), and Japan’s National Institutes of Natural Sciences (NINS), working together with the Republic of Chile.
In Sweden, Onsala Space Observatory at Chalmers University of Technology has played a role in ALMA from the very beginning. Among its contributions are specialized receivers built for the telescope. Onsala also hosts the Nordic ALMA Regional Centre, which offers technical expertise for the project and helps astronomers across the Nordic countries make full use of ALMA’s capabilities.
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