Compared to Earth, the Sun is fantastically large, but tons of other stars in the cosmos are even larger—by a lot. The Hubble Space Telescope recently photographed the Tarantula Nebula in the Large Magellanic Cloud, where there is a cluster of nine stars that are each more than 100 times more massive than the Sun and together shine 30 million times brighter.

Astronomers combined images taken with the telescope's Wide Field Camera 3 with the ultraviolet capabilities of the Space Telescope Imaging Spectrograph to identify for the first time nine "monster stars" in a cluster known as R136. According to a press statement from NASA and the European Space Agency, which jointly operate Hubble, the discovery is the largest sample of very massive stars identified to date. Hubble was also able to identify dozens of other stars in the cluster that are 50 times the mass of our Sun. R136a1, a previously identified star 250 times the mass of the Sun, is also a part of the photographed Tarantula Nebula, and the astronomers report that it is still on record as the most massive star known in the universe.

Left: Central part of R136 as seen in ultraviolet. Right: Pseudo-image created by SITI UV spectra. Image credit: ESA/Hubble, NASA, K.A. Bostroem (STScI/UC Davis)

University of Sheffield's Paul Crowther told BBC News that the monster stars are all close to the maximum luminosity that a star can have before it is ripped apart—a phenomenon known as the Eddington limit. Crowther added that the stars are losing the equivalent of the Earth's mass in gaseous material each month, and because they are shining so brightly, they will burn out in the next few million years. The stars will be in pairs when they die and will turn into black holes, Crowther said, which will merge and cause gravitational waves to form.

Astronomers know where the stars are in space, and they can theorize about when they will burn out, but the question of where the monsters came from is a mystery that will take more time to solve. "There have been suggestions that these monsters result from the merger of less extreme stars in close binary systems," study co-author Saida Caballero-Nieves 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."

To read more about the discovery, head to the Hubble Space Telescope website.