A collaboration of teams at the Open University, University of Central Lancashire and the Rutherford Appleton Laboratory have discovered 122 new eclipsing binary systems and observed hundreds more variable stars, thanks to a survey using NASA’s two STEREO solar satellites. The finding was presented by Dr Danielle Bewsher of the University of Central Lancashire last week at the National Astronomy Meeting in Llandudno, North Wales.

STEREO, which stands for Solar TErrestrial RElations Observatory, is a solar observation mission that was launched in 2006. Both spacecraft comprising the mission carry a Heliocentric Imager (HI) with cameras (HI-1 and HI-2I) built and developed at the STFC’s Rutherford Appleton Laboratory and the University of Birmingham. The stability of the cameras has allowed both 3D studies of the Sun and observations of coronal mass ejections, which are the cause of space weather, to be made. It is this steadiness that Bewsher and her colleagues have recognised, leading them to monitor variations of the brightness of stars. “To date, 893,000 stars have passed through the HI-1 field-of-view alone, producing an unexpected resource of data about the variability of stars that is currently being mined,” says Bewsher.

Karl Wraight, the lead author of the paper that details the research, discovered the 122 eclipsing binaries during an initial analysis of the data and expects many more to be found. “STEREO’s ability to sample continuously for up to 20 days, coupled with repeat viewings from the twin spacecraft during the year, makes it an invaluable resource for researching variable stars,” says Wraight, who is an STFC PhD student at the Open University. “As well as making discoveries, observations from the Heliocentric Imager are enabling us to pin down the periods of known variables with much greater accuracy.”

The collaboration of scientists, which includes Professor Glenn White of the Open University, believe that the STEREO measurements can be used for exoplanet and astroseismology research. “Very small changes to the brightnesses of stars can be detected,” says White, a research group leader at the Rutherford Appleton Laboratory. “This could reveal the presence of transiting exoplanets, or be used to trace a star’s internal structure by measuring their seismic activity.”