Among stars, heavyweight champ

Astronomers have discovered a star about 265 times the mass of the sun, more massive than any other star known in the universe. At birth, the hefty body tipped the scales at 320 suns, more than twice the generally accepted limit for a newborn.

Paul Crowther of the University of Sheffield in England and colleagues describe the star in an upcoming Monthly Notices of the Royal Astronomical Society.

Crowther and collaborators examined massive stars in two clusters, one in the Milky Way and the other in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. The team used the European Southern Observatory’s Very Large Telescope atop Cerro Paranal in Chile and looked at archival data from the Hubble Space Telescope. Four stars in the Large Magellanic Cloud cluster, dubbed R136, had temperatures more than seven times that of the sun and were several million times brighter and tens of times larger.

Those properties, combined with the age of the four stars, indicate that each weighed more than 150 suns at birth. One, R136a1, was more than twice that mass when it formed, the researchers calculate. The results suggest that present-day stars may become as heavy as 300 suns. Theoretical studies indicated that such heavyweights could have formed only during the first few hundred million years of the universe, when its chemical makeup favored formation of massive stars.

Stars from eight to 150 sun masses eventually die as supernovas. Stars from 150 to 300 suns may end their brief lives in bigger explosions known as pair-instability supernovas, once thought to have occurred only in the early universe.