Most Massive Star Detected

Get big, die young. Such is the fate of behemoth stars, the largest of which are about 150 times the mass of the sun. A new study, however, finds evidence for stars more than twice that size, including an uber-giant so luminous that it makes the light of our sun look no brighter than the glow of the full moon in comparison.

Isolating the light of the biggest stars is a difficult and tedious process. Massive stars are rare, distant, short-lived and crammed inside dense clusters that are shrouded in dust. In the past, reports of stars up to 2,000 times the size of the sun all turned out to be clusters of stars, not single, massive objects.

"People have been trying to find the most massive star and to determine the upper mass limit of stars, but it's like prospecting for gold. You have to sift through a whole lot of junk and there's also a lot of fool's gold," said Rochester Institute of Technology astronomer Donald Figer. 

Armed with new high-resolution imagery, an international team of astronomers is throwing down the gauntlet again with studies on NGC 3603, a very young star cluster located about 22,000 light-years away in the Milky Way's Carina spiral arm, and RMC 136a, which resides in the Tarantula Nebula, located 165,000 light-years away in our neighbor galaxy, the Large Magellanic Cloud.

In addition to chemical analysis and precision position measurements, astronomers checked they weren't seeing binary pairs by scanning for telltale X-rays that would come from the clash of solar winds. They didn't find any, leading the team to conclude that they had, in fact, uncovered several stars in the Large Magellanic Cloud cluster which began their lives between 165 and 320 times the mass of the sun.

Among their findings, the star R136a1, found in the R136 cluster, is the most massive star ever found, with a mass of about 265 solar masses and with a birthweight of as much as 320 times that of the sun.

The Milky Way's giant stars were more modest -- 105 to 170 solar masses -- and were included to validate computer models that also were used in the study.

"We can rule out that we have two stars close by," Raphael Hirschi, an astrophysicist with Keele University in the United Kingdom, told Discovery News. "We have achieved a high enough resolution to definitely rule out that it might be a cluster of stars."

Lead scientist Paul Crowther, at the University of Sheffield in the United Kingdom, said stars about 300 solar masses could be the new limit, at least in our corner of the universe.

"We considered stars with 1,000 solar mass, but there weren't any clusters big enough. You don't get big stars in small clusters," Crowther told Discovery News.

Figer, for one, isn't convinced.

"The claims in the paper rely on a series of assumptions and uncertain models, and there are possible interpretations that are not discussed,"  he wrote in an email to Discovery News. "It would be interesting to see another study that could examine these claims."

The study appears in the Monthly Notices of the Royal Astronomical Society.