Since the online citizen-science project "Planet Hunters" launched in December 2011, 40,000 global web users have been helping professional astronomers analyze the light from 150,000 stars in the hopes of discovering Earth-like planets orbiting them.
Users analyze real scientific data collected by NASA's Kepler mission, which has been searching for planets beyond our own solar system--called exoplanets--since its launch in March 2009.
Now astronomers at Yale University have announced the discovery of the first two potential exoplanets discovered by Planet Hunters users in a study published in the Monthly Notices of the Royal Astronomical Society.
"This is the first time that the public has used data from a NASA space mission to detect possible planets orbiting other stars," says Yale astronomer and exoplanet expert Debra Fischer, who helped launch the Planet Hunters project.
The candidate planets orbit their host stars with periods ranging from 10 to 50 days--much shorter than the 365 days it takes Earth to orbit the Sun--and have radii that range in size from two-and-a-half to eight times Earth's radius. Despite those differences, one of the two candidates could be a rocky planet similar in size to Earth (as opposed to a giant gas planet like Jupiter), although they aren't in the so-called habitable zone where liquid water, and therefore life as we know it, could exist.
Next, the Planet Hunters team--a collaboration between astronomers at Yale, the University of Oxford, and the Adler Planetarium in Chicago--used the Keck Observatory in Hawaii to analyze the host stars. "I think there's a 95% chance or greater that these are bona fide planets," Fischer says.
The Kepler team has already announced the discovery of 1,200 exoplanet candidates and will follow up on the highest potential ones with further analysis, but they had discarded the two found by Planet Hunters users for various technical reasons that led them to believe they weren't promising candidates. …