The newly identified Stephenson 2 DFK 52, an extraordinary red supergiant, is situated within the expansive stellar cluster RSGC2.
This image showcases the red supergiant star Stephenson 2 DFK 52 and its surroundings. Image credits: Alma / ESO / NAOJ / NRAO / Siebert et al.
RSGC2 is a cluster containing at least 26 red supergiants located at the base of the Milky Way’s diagonal crux spiral arm, approximately 5,800 parsecs (18,917 light-years) away.
Also referred to as Stephenson 2, this cluster is an active site for recent star formation where the arms intersect with galaxy bulges.
A team of astronomers led by Mark Siebert from Chalmers University of Technology observed the RSGC2 star using the Atacama Large Millimeter/submillimeter Array (ALMA).
“What we catch in this image of Stephenson 2 DFK 52 is indeed a supermassive red star that is shedding clouds of gas and dust as it approaches the end of its lifecycle,” they explained.
“Such nebulae are typically found around supermassive stars; however, this particular cloud presents an intriguing mystery for astronomers.”
“This cloud of ejected material is the most expansive discovered around a giant star, spanning an impressive 1.4 light-years.”
“Stephenson 2 DFK 52 is quite similar to Betelgeuse, another renowned red supergiant, so we anticipated observing a comparable cloud surrounding it.”
“If Stephenson 2 DFK 52 is as close to us as Betelgeuse, the surrounding cloud would appear about one-third the size of the full moon.”
Recent observations from ALMA have enabled astronomers to quantify the mass of material enveloping the star and analyze its velocity.
“Regions moving towards us appear in blue, while those receding are represented in red,” they stated.
“The data suggests that the star experienced a significant mass loss event about 4,000 years ago, followed by a slow-down in its current mass loss rate.”
The team estimates that Stephenson 2 DFK 52 has a mass between 10-15 solar masses and has already lost 5-10% of its mass.
“The rapid expulsion of such materials within a brief time frame poses a mystery,” the researchers commented.
“Could an unusual interaction with a companion star be responsible? Why does the cloud exhibit such a complex shape?”
“Understanding why Stephenson 2 DFK 52 has expelled so much material can illuminate insights into its eventual fate.
The team’s paper is set to be published in the journal Astronomy and Astrophysics.
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Mark A. Sheebert et al. 2025. Discovery of the extraordinary red supergiant Stephenson 2 DFK 52 within the expansive stellar cluster RSGC2. A&A in press; Arxiv: 2507.11609
Source: www.sci.news
