Exoplanet search finds way to rule out planet-eating suns

New Scientist : A study of the chemical composition of two Sun-like stars, HD 20781 and HD 20782, indicates that they may have accreted several Earth-sized planets over their lifetimes. Therefore, they may not be the best candidates to study in the search for habitable worlds. Although stars tend to be composed primarily of hydrogen and helium, they often have on their surfaces trace elements absorbed from other orbiting bodies. Using the telescopes at the Las Campanas Observatory in Chile, Keivan Stassun of Vanderbilt University and colleagues found that HD 20781 and HD 20782 had unusually high levels of some 15 elements, including aluminum, silicon, calcium, and iron, which indicates that they have accreted an estimated 30 Earth masses between them. The researchers propose that the Earth-like planets were pushed too close to their stars by the larger, Jupiter-like planets still in orbit. Because hunting for exoplanets has proven to be time-consuming, astronomers hope to speed up the process by finding a way to quickly rule out stars that tend to devour their planets.