Supergiant star survived a violent eruption - but what comes next?

A red supergiant in the Milky Way has thrown a curveball at astronomers. DFK 52, a member of the Stephenson 2 cluster, sits inside a vast bubble of gas and dust that is about 8.2 trillion miles across and roughly the mass of the Sun.

Researchers used the ALMA radio telescope in Chile to observe the red supergiant, which is similar to the well-known star Betelgeuse. The project was led by Mark Siebert at Chalmers University of Technology.

ALMA revealed that the bubble is expanding, suggesting a violent outburst about 4,000 years ago that somehow did not end the star’s life.

Star bubble shows huge mass outburst

The team describes a complex cloud that spreads outward in tangled arcs and clumps, not a tidy sphere, and reaches astonishing size for material tied to a single star.

The experts report that the detached shell holds roughly one solar mass and extends about 1.4 light years across.

The researchers link the expansion to a short, intense episode of mass loss that happened a few millennia ago. That timing is recent in astronomical terms and sets up a natural test case for how massive stars shed material before they explode.

“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,” said Siebert.

What the radio telescope saw

The ALMA array measures faint radio light from molecules like carbon monoxide and silicon monoxide, letting astronomers map gas speeds with the Doppler effect. Those data reveal both slow and fast components moving in different patterns around the star.

A compact, slower wind surrounds the star today at about 6.2 miles per second. A faster structure, likely a disk or ring oriented edge on, expands at about 16.8 miles per second and appears to be the relic of the ancient outburst.

This two-part picture matches the brightness and shape of the carbon monoxide emission. The model points to an equatorial feature containing only a few hundredths of the Sun’s mass, along with a slower, continuous wind shedding material at a modest rate.

Why the star lost mass

Why did DFK 52 throw off so much mass without dying? The survival of the star after such a forceful ejection raises questions about what set off the event.

“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,” said Siebert.

The idea of a hidden partner that stirred the atmosphere and helped peel off outer layers has gained traction. 

Another possibility is a brief, unstable phase within the star itself. Episodic mass loss has been seen or inferred in other massive stars approaching the end of life, though the precise triggers remain debated.

What this means for future supernovae

Dense gas and dust close to a star can change how a supernova looks in its first days. When fresh ejecta slam into nearby material, the interaction can brighten the event and imprint unique features on the early spectrum.

Evidence for this behavior already exists. A 2017 paper on SN 2013fs showed that the exploding star had a compact but dense circumstellar medium that was shed shortly before the blast.

DFK 52’s bubble sits farther out, yet it proves the star has a history of strong mass loss. If the star ramps up again before it dies, the environment could set the stage for a very conspicuous supernova.

Comparing the star to other supergiants

DFK 52 draws comparisons to red supergiant icons like Betelgeuse and Antares. These are massive, swollen, cool stars nearing the end of their lives and expected to finish as Type II supernovae.

Betelgeuse itself showed how messy these stars can be when it dimmed in late 2019 and early 2020. That event was traced to a dust cloud formed by material leaving the star.

DFK 52 appears less luminous than the most extreme red supergiants but carries a larger, colder envelope at great distance. This combination hints at an unusual history that standard wind models do not capture.

What happens next

The team plans follow up observations to hunt for a companion and to refine the 3D structure of the shell. Better constraints on the gas chemistry and dust properties will also help sort out how the outburst unfolded.

“If this is a typical red supergiant, it could explode sometime in the next million years,” said study co-author Elvire De Beck.

“We’re planning more observations to understand what’s happening, and to find out whether this might be the Milky Way’s next supernova.”

The study is published in Astronomy and Astrophysics.

Image Credit: ALMA (ESO/NAOJ/NRAO)/M. Siebert et al

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–