So-called 'citizen scientists' may have found two new planets previously dismissed as possibilities by NASA.
Since the beginning of this year, the Planet Hunters project has pulled in 40,000 web users from around the world to help professional astronomers analyze the light from 150,000 stars.
They analyze scientific data collected by NASA's Kepler mission, with the aim of identifying planets orbiting other stars - and seem to have come up trumps already.
"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 project.
"I think there's a 95 percent chance or greater that these are bona fide planets."
The candidate planets orbit their host stars with periods somewhere between 10 and 50 days, and are between two-and-a-half and eight times Earth's radius. One could be a rocky planet similar in size to the Earth - although neither is in the habitable zone where liquid water, and therefore life as we know it, could exist.
The Kepler team has already announced the discovery of 1,200 exoplanet candidates and is following up on those that look most plausible. However, the team had discarded the two found by the Planet Hunters for various technical reasons that led them to believe they weren't promising candidates.
"These three candidates might have gone undetected without Planet Hunters and its citizen scientists," says Meg Schwamb, a Yale researcher and Planet Hunters co-founder.
"Obviously Planet Hunters doesn't replace the analysis being done by the Kepler team. But it has proven itself to be a valuable tool in the search for other worlds."
Users found the two candidates in the first month of operations using data from the Kepler mission. The Kepler team analyzed ten possibilities flagged up by the Planet Hunters, and determined that two of the 10 met the criteria for being classified as planet candidates.
The two were tipped as potential planets by several dozen different users, as the same data's analyzed by more than one user.
Planet Hunters users are now sifting through the next 90 days of Kepler data in the hopes of adding to the tally.
"This is what we found after just a preliminary glance through the first round of Kepler data," Fischer said. "There's no doubt that, with each new round of data, there will be more discoveries to come."