Nine monster stars have been spotted huddling together in a nest by astronomers using the Hubble Space Telescope. The family of superstars, each having masses more than 100 times that of our own sun, was uncovered sitting in the Tarantula Nebula.
Astronomers are puzzled why R136, sitting within the nebula, hosts such a large collection of monster stars. The formation sits roughly 170,000 light years from Earth, and most of the energy released by the monster stars is in the form of ultraviolet radiation.
The Wide Field Camera 3 (WFC3) and Space Telescope Imaging Spectrograph (STIS) aboard the Hubble were utilized in the study of the bunching of stars. These instruments were able to investigate ultraviolet light emitted by the massive stellar bodies.
Just one star in the system, R136a1, is the largest star ever seen in the universe — around 250 times the mass of our own sun. Seen together, the nine supermassive stars produce 30 million times as much energy as our stellar companion.
The lifetime of stars is determined solely by their mass, with low-mass stars existing for the longest amount of time before meeting their final fate. These stars, among the largest in the universe, are destined to lead exceedingly short lives (for stars), indicating this formation must be young. However, the processes that led to their formation remain a mystery.
"There have been suggestions that these monsters result from the merger of less extreme stars in close binary systems. 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," said Saida Caballero-Nieves of the University of Sheffield.
When stars containing more than 10 times the mass of the sun collapse at the end of their existence after two to three million years, they form black holes, bodies so dense that even light cannot escape. Astronomers will continue to examine R136 in an effort to find pairs of binary black holes. These bodies could merge, creating gravitational waves that would echo throughout space.
Evidence exists for even more massive stars in the universe, beyond the sight of Hubble. Those discoveries await even more powerful observatories in the future, including the James Webb space Telescope (JWST), due for launch in 2018.
Investigation of the massive stars in R136 will be published in the Monthly Notices of the Royal Astronomical Society.