Researchers have spotted a cosmic ballet — two stars spinning around one another while both orbiting a larger star. The trio, named KOI-126, provided a rare opportunity to precisely measure the masses of binary stars.

The triple system is about 1,000 parsecs from Earth. The smaller duo have masses of about one-fifth and one-quarter that of the Sun, and orbit one another in 1.76 days. They take about 34 days to go around their larger partner, which has a mass 1.3 times that of the Sun. Joshua Carter of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and his team calculated the masses using the space-based Kepler telescope by observing the dimming of light as the binary stars passed in front of the larger star. They produced a model that fitted the data to determine the dynamics and characteristics of the low-mass pair.

Science doi:10.1126/science.1201274 (2011)