Astronomers say they have discovered the most colossal star on record, in a region of space known as the Tarantula nebula in a neighbouring galaxy to our own.

The record-breaking star weighs 265 times as much as the sun and is millions of times brighter, they said.

The discovery has astonished scientists who thought it was impossible for stars to exceed more than 150 times the mass of the sun.

When the star was born it could have been more than twice as heavy.

Because it is so far away - about 165,000 light-years - it can only be seen with the use of powerful telescopes in the southern hemisphere. If the star, known as R136a1, took the place of the sun in our solar system, its gravitational attraction would pull our planet in so close that the length of an “Earth year” would shrink to three weeks.

“It would bathe the Earth with incredibly intense ultraviolet radiation, rendering life on our planet impossible,” said Raphael Hirschi, a researcher at Keele University in Staffordshire, England.

A team led by Paul Crowther, an astrophysicist at Sheffield University, also in the U.K., used the Very Large Telescope (VLT) in the Atacama desert of northern Chile and archival material from the Hubble space telescope to study two young clusters of stars called NGC 3603 and RMC 136a.

The first group of stars, NGC 3603, lies about 22,000 light-years away, while stars in the RMC136a cluster are in a neighbouring galaxy called the Large Magellanic Cloud.

The astronomers found a clutch of monster stars, including several that are tens of times larger than the sun and several millions of times brighter. Some have surface temperatures of more than 40,000C - seven times hotter than our own sun.

These enormous stars churn out vast quantities of material, and, close up, would look fuzzy compared to the sun. “Unlike humans, these stars are born heavy and lose weight as they age,” said Dr. Crowther. “Being a little over a million years old, the most extreme star, R136a1, is already ‘middle-aged’ and has undergone an intense weight-loss programme, shedding a fifth of its initial mass over that time, or more than 50 solar masses.”

Such heavyweight stars are extremely rare, forming only within the densest star clusters. Distinguishing the individual stars was made possible by the use of infra-red instruments on the telescope.

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

Copyright: Guardian News & Media 2010

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