A STEREO/HI-1A image taken March 7, 2010, (left) highlights two variable stars. The varying brightness of the two stars, V837 Tau and V1129 Tau are shown at right.
Photo by D. Bewsher (UCLan)/NASA/STEREO and the HI instrument team
Researchers have discovered more than a hundred new eclipsing binary stars and observed hundreds more variable stars in an innovative survey using NASA’s two STEREO solar satellites. A team from the Open University, University of Central Lancashire, and the Science and Technology Facilities Council (STFC) Rutherford Appleton Laboratory carried out the study.
STEREO was launched in 2006 to study the Sun in 3-D as well as coronal mass ejections, the cause of space weather. Each STEREO spacecraft carries a Heliospheric Imager (HI), each instrument comprising two cameras (HI-1 and HI-2) built and developed at the STFC’s Rutherford Appleton Laboratory and the University of Birmingham. The HI cameras are able to make such stable measurements that researchers can accurately monitor the brightness of stars in the background.
“Although STEREO is primarily a solar mission, we recognized that the stability of the HI cameras could also be used to monitor variations of the brightness of stars,” said Danielle Bewsher of the University of Central Lancashire. “To date, 893,000 stars have passed through the HI-1 field of view alone, producing an unexpected resource of scientific data about the variability of stars that is currently being data mined.”
The lead author of the study, Karl Wraight, an STFC Ph.D. student at the Open University, has found 122 new eclipsing binaries during an initial analysis of the data, and expects many more to be discovered.
“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,” Wraight said. “As well as making discoveries, observations from HI are enabling us to pin down the periods of known variables with much greater accuracy.”
In addition to studying variable stars, the team believes that HI measurements may be used for exoplanet and asteroseismology research.
“Very small changes to the brightnesses of stars can be detected, which could reveal the presence of transiting exoplanets, or be used to trace a star’s internal structure by measuring their seismic activity,” said Glenn White of the Open University and Rutherford Appleton Laboratory.