Watching the violent death of a very giant star is rare

Artist’s impression of the red giant star VY Canis Majoris. VY Canis Majoris is located about 3,009 light-years from Earth and is probably the most massive star in the Milky Way. Image Credit: NASA / ESA / Hubble / R. Humphreys, University of Minnesota / J. Olmsted, STScI / hublesite.org

By tracking molecular emissions in outflows around the red giant star VY Canis Majoris, astronomers have obtained the first detailed map of the star’s atmosphere, which sheds light on the mechanisms involved in the extreme giant star’s final stages.

A team of astronomers led by the University of Arizona has created a detailed 3D image of a dying giant star. The team, led by UArizona researchers Ambesh Singh and Lucy Ziurys, tracked the distribution, directions, and velocities of a variety of particles surrounding a red giant star known as VY Canis Majoris.

Their findings, which they presented on June 13, 2022, at the 240th meeting of the American Astronomical Society in Pasadena, California, offer insights, on an unprecedented scale, about the processes that accompany the death of giant stars. Working with collaborators was Robert Humphreys of the University of Minnesota and Anita Richards of the University of Manchester in the United Kingdom.

Extreme giant stars known as hypergiants are very rare, and only a few are known about them[{” attribute=””>Milky Way. Examples include Betelgeuse, the second brightest star in the constellation Orion, and NML Cygni, also known as V1489 Cygni, in the constellation Cygnus. Unlike stars with lower masses – which are more likely to puff up once they enter the red giant phase but generally retain a spherical shape – hypergiants tend to experience substantial, sporadic mass loss events that form complex, highly irregular structures composed of arcs, clumps, and knots.

Located about 3,009 light-years from Earth, VY Canis Majoris – or VY CMa, for short – is a pulsating variable star in the slightly southern constellation of Canis Major. Spanning anywhere from 10,000 to 15,000 astronomical units (with 1 AU being the average distance between Earth and the sun) VY CMa is possibly the most massive star in the Milky Way, according to Ziurys.

“Think of it as Betelgeuse on steroids,” said Ziurys, a Regents Professor with joint appointments in UArizona Department of Chemistry and Biochemistry and Steward Observatory, both part of the College of Science. “It is much larger, much more massive and undergoes violent mass eruptions every 200 years or so.”

The team chose to study VY CMa because it is one of the best examples of these types of stars.

“We are particularly interested in what hypergiant stars do at end of their lives,” said Singh, a fourth-year doctoral student in Ziurys’ lab. “People used to think these massive stars simply evolve into supernovae explosions, but we are no longer sure about that.”

“If that were the case, we should see many more supernovae explosions across the sky,” Ziurys added. “We now think they might quietly collapse into black holes, but we don’t know which ones end their lives like that, or why that happens and how.”

Previous imaging of VY CMa with