Hubble finds cluster of massive stars in distant galaxy

The image shows the central region of the Tarantula Nebula in the Large Magellanic Cloud. The young and dense star cluster R136 can be seen at the lower right of the image. This cluster contains hundreds of young blue stars, among them the most massive star detected in the Universe so far. (NASA, ESA, P Crowther, University of Sheffield)

Astronomers using the Hubble Space Telescope have spotted the largest collection of monster stars – objects with masses over 100 times greater than the sun.

The international team has found five of these massive stars to go with four discovered earlier in cluster R136. The cluster, only a few light years across, is located in the Tarantula Nebula within the Large Magellanic Cloud, about 170,000 light-years away.

Not only are they big but these stars are incredibly bright, researchers said. Together, these nine stars outshine the Sun by a factor of 30 million.

The cluster was found thanks the ultraviolet capabilities of the Hubble and its Space Telescope Imaging Spectrograph and the findings will be published in the Monthly Notices of the Royal Astronomical Society.

“The ability to distinguish ultraviolet light from such an exceptionally crowded region into its component parts, resolving the signatures of individual stars, was only made possible with the instruments aboard Hubble,” Paul Crowther from the University of Sheffield, and lead author of the study, said in a statement.

In 2010 Crowther and his collaborators stunned the astronomy world with the discovery of four stars within R136, each with over 150 times the mass of the Sun. The findings came as a surprise, since they exceeded the upper-mass limit for stars believe to be possible at the time.

Researchers said their findings are not only showing that stars are much bigger than earlier believed but also helping to understand how they get so large. They also were able to investigate outflows from these behemoths, which are most readily studied in the ultraviolet. They eject up to an Earth mass of material per month at a speed approaching one percent of the speed of light, resulting in extreme weight loss throughout their brief lives.

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“There have been suggestions that these monsters result from the merger of less extreme stars in close binary systems,” Saida Caballero-Nieves, a co-author of the study, said. “From what we know about the frequency of massive mergers, this scenario can’t account for all the really massive stars that we see in R136, so it would appear that such stars can originate from the star formation process.”