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7.21.2010 Largest ever star discovered

By Staff Writer

Astronomers have discovered the biggest star ever - more than 300 times the mass of the Sun, and twice as large as the generally accepted limit of 150 solar masses.

A team led by Paul Crowther, professor of astrophysics at the University of Sheffield, used ESO’s Very Large Telescope (VLT) and archival data from the Hubble Space Telescope to study two young clusters of stars, NGC 3603 and RMC 136a.

R136a1, found in the R136 cluster, is the most massive star ever found, with a current mass of about 265 solar masses and a birthweight of as much as 320 solar masses.

Very massive stars produce very powerful outflows. "Unlike humans, these stars are born heavy and lose weight as they age," says Crowther.

"Being a little over a million years old, the most extreme star R136a1 is already middleaged, and has undergone an intense weight loss programme, shedding a fifth of its initial mass over that time, or more than fifty solar masses."

These super-heavyweight stars are extremely rare, forming only within the densest star clusters.

And understanding how they form is puzzling. "Either they were born so big or smaller stars merged together to produce them," says Crowther.

Not only is R136a1 the most massive star ever found, but it also has the highest luminosity too - close to 10 million times greater than the Sun.

"Owing to the rarity of these monsters, I think it is unlikely that this new record will be broken any time soon," says Crowther.