A red supergiant star that is 1,500 times larger than the sun is in its death-throes. Scientists rarely see the demise of such massive stars, and they stand to learn a lot from the data.
The largest known star in the galaxy, parked in a star cluster some 16,000 light-years away, has exhausted its hydrogen fuel and is shedding gas in a signal that the end is near – at least on cosmic timescales.
The star, a red supergiant, is surrounded by clouds of glowing hydrogen, providing a rare opportunity to observe a massive star during such an early stage in its prolonged demise – a path slated to end with the star's catastrophic collapse and the subsequent explosion at its core, known as a supernova.
Such explosions seed the galaxy with chemical elements heavier than hydrogen and helium. These elements form in the fusion furnaces at the heart of stars. The elements get ejected into interstellar space by stellar winds as well as by events that occur at the end of a star's life. They become the raw material for building other objects in the cosmos – from planets to people.
Studying gas clouds such stars release as they lose mass can yield insights into the physical processes at work as well as clues as to the kind of compact object – a neutron star, or perhaps a black hole – the star's core could become after its explosive end.
Some of the massive stars that end their runs as core-collapse supernovae "have lost a lot of mass close to their end," writes Jeremy Drake, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and a member of the research team reporting the results.
"It would be very interesting to catch one in such a mass-loss phase," he writes in an e-mail. At the same time, he adds, estimated of such losses are very uncertain and can have a profound effect on the future course of the star's evolution.
Studying stars like W26 and its nebula can help refine those estimates, he notes.
But detecting the clouds of hot, glowing gas around such massive stars is rare, the researchers say, adding that no one has observed such gas clouds around a red supergiant before.