Astronomers from Chalmers University of Technology (Sweden) have discovered a unique structure around the red supergiant DFK 52 in the Milky Way — a giant bubble of gas and dust, the largest known in our galaxy. Its mass is comparable to that of the Sun, and its diameter reaches 1.4 light-years. The study, published in Astronomy & Astrophysics (A&A) on August 20, 2025, raises questions about the nature of the star and its future.

The Discovery of the Bubble

The observations were carried out with the Atacama Large Millimeter/submillimeter Array (ALMA), which allowed scientists to study the surroundings of DFK 52 — a red supergiant located in the constellation Cassiopeia, about 12,000 light-years from Earth. The star resembles the famous Betelgeuse but stands out with an enormous cloud of matter surrounding it.

“We were surprised when we saw the ALMA data. This star is almost a twin of Betelgeuse, but it is enveloped in a huge, chaotic cloud of material,” said the study’s lead researcher, Marc Siebert.

The bubble consists of gas and dust expelled by the star around 4,000 years ago during a powerful eruption. The ejected material is equivalent in mass to the Sun, and the scale of the structure makes it the largest of its kind in the Milky Way. For comparison, the bubble’s diameter is three times greater than the distance from the Sun to Pluto.

The Mystery of the Ejection

Red supergiants like DFK 52 are massive stars (8–20 times more massive than the Sun) in the late stages of their evolution. Normally, they shed their outer layers before exploding as supernovae, which mark their death. However, DFK 52 remains active, making its case unique.

ALMA data showed that the bubble continues to expand at about 10 km/s. Scientists hypothesize that the mass ejection may have been triggered by the gravitational influence of a “hidden” companion — either another star or possibly a black hole — that affected the supergiant’s evolution. So far, there is no direct evidence for such a companion, but further observations may clarify the situation.

Significance for Astronomy

The discovery of the bubble around DFK 52 has several important implications:

  • Stellar evolution: The structure confirms that red supergiants can lose a significant portion of their mass before exploding as supernovae, which impacts their life cycle.
  • Potential supernova: Scientists believe DFK 52 could be the next supernova in the Milky Way. While the timing is uncertain, it could happen within the next few hundred thousand to a million years.
  • Uniqueness of the system: A bubble of this scale is extremely rare, even for red supergiants, making DFK 52 an important object for studying star formation and stellar evolution.

“We plan new observations to better understand what is happening and to determine whether DFK 52 might indeed become the Milky Way’s next supernova. If this star is typical, its demise could come within the next million years,” explained astronomer Elvire De Beck.

Why It Matters

Red supergiants like DFK 52 play a key role in enriching the galaxy with heavy elements. Their supernova explosions scatter carbon, oxygen, iron, and other elements necessary for the formation of planets and possibly life. Studying such stars helps us understand how massive stars evolve and how their outflows shape their cosmic environments.

In addition, the bubble around DFK 52 may provide clues about the dynamics of stellar winds and the interaction of supergiants with their surroundings. If the companion hypothesis is confirmed, it would mark an important discovery pointing to complex evolutionary scenarios in binary systems.

In Brief

The discovery of a giant bubble around the red supergiant DFK 52 — the largest such structure in the Milky Way — has become a sensation in astronomy. With a mass comparable to the Sun’s and a diameter of 1.4 light-years, the bubble points to a massive eruption about 4,000 years ago. Scientists suggest that a hidden companion may have influenced the event, and the star itself is on its way to a supernova explosion. Future ALMA observations will help uncover the mysteries of DFK 52 and its potential role as the galaxy’s next “cosmic explosion.”