Using the NASA/ESA Hubble Space Telescope, astronomers have identified nine extremely massive stars in the young star cluster R136.

R136, also known as RMC 136, is a massive, young stellar grouping about 170,000 light-years away.

The cluster is only a few light-years across and is only a few million years old. It resides in the Tarantula Nebula (30 Doradus), a turbulent star-birth region in the Large Magellanic Cloud, a satellite galaxy of our Milky Way Galaxy.

According to an international team of astronomers, led by Prof. Paul Crowther from the University of Sheffield, R136 hosts at least nine very massive stars — over 100 times more massive than the Sun — as well as dozens of stars exceeding 50 solar masses.

“There have been suggestions that these monsters result from the merger of less extreme stars in close binary systems,” said team member Dr. Saida Caballero-Nieves, also from the University of Sheffield.

“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.”

The detected stars are not only extremely massive, but also exceptionally bright and together the nine massive stars outshine the Sun by a factor of 30 million.

The results were published online February 5, 2016, in the Monthly Notices of the Royal Astronomical Society.

In order to find answers about the origin of these massive stars, Prof. Crowther and his colleagues will continue to analyze the datasets gathered.

“Despite the new discovery the current record holder R136a1 does keep its place as the most massive star known in the Universe at over 250 solar masses,” they said.

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Paul A. Crowther et al. The R136 star cluster dissected with Hubble Space Telescope/STIS. I. Far-ultraviolet spectroscopic census and the origin of He ii λ1640 in young star clusters. MNRAS, published online February 5, 2016; doi: 10.1093/mnras/stw273