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Big Stars. Really Big.

New Scientist

Astronomers hunting massive stars in a bid to understand the early Universe have set a new record.

In April, Gregor Rauw, of the University of Liege in Belgium, and colleagues suggested that an object called WR 20a in the constellation Carina could be two giant stars orbiting each other. That would explain its otherwise puzzling spectrum of light. Now further observations by Alceste Bonanos and colleagues at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, show Rauw's team were right.

They analysed the variation in brightness of WR 20a for 17 nights using the 1.3-metre Warsaw telescope at the Los Campanas Observatory in La Serena, Chile. The observations indicate that each star weighs 80 solar masses - the previous record was about 60 solar masses. The pair take just 3.7 days to orbit their common centre and partially eclipse each other every orbit.

It is the dimming of light caused by the partial eclipses that enables astronomers to determine their mass and orbit. "We can only measure masses of stars accurately in binary systems," says Bonanos.

Finding and weighing giant stars has become a major activity for astronomers who want to know if the first generation of stars could have been short-lived giants up to 300 times the mass of our Sun.

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