Citizen Scientists Spot Planet Orbiting Two Stars

Lee Rannals for redOrbit.com – Your Universe Online

A team of international astronomers, along with Planethunters.org volunteers, found the first reported case of a planet orbiting twin suns that in turn is orbited by a second distant pair of stars.

Researchers said that only six planets are known to orbit two stars, and none of these are orbited by distant stellar companions.

“Circumbinary planets are the extremes of planet formation,” said Meg Schwamb of Yale University and lead author of a paper presented Oct. 15 at the annual meeting of the Division for Planetary Sciences of the American Astronomical Society in Reno, Nevada. “The discovery of these systems is forcing us to go back to the drawing board to understand how such planets can assemble and evolve in these dynamically challenging environments.”

The planet was first identified by citizen scientists participating in Planet Hunters, which is a Yale-led program that asks for the public’s help to review astronomical data from NASA’s Kepler spacecraft.

The volunteers first spotted faint dips in light caused by the planet as it passed in front of its parent stars.

“Planet Hunters is a symbiotic project, pairing the discovery power of the people with follow-up by a team of astronomers,” said Debra Fischer, a professor of astronomy at Yale and planet expert who helped launch Planet Hunters in 2010. “This unique system might have been entirely missed if not for the sharp eyes of the public.”

PH1 is a gas giant with a radius about 6.2 times that of Earth, and it orbits outside the 20-day orbit of a pair of eclipsing stars that are 1.5 and 0.41 times the mass of the Sun.

The planet revolves around its host stars about every 138 days at about 1,000 times the distance of the Earth and the Sun.

“The thousands of people who are involved with Planet Hunters are performing a valuable service,” coauthor Jerome Orosz, an associate professor of astronomy at San Diego State University, said in a press release. “Many of the automated techniques used to find interesting features in the Kepler data don’t always work as efficiently as we would like. The hard work of the Planet Hunters helps ensure that important discoveries are not falling through the cracks.”

Robert Gagliano, one of the volunteers, said he was ecstatic to spot a small dip in the eclipsing binary star’s light curve from the Kepler telescope.

Kian Jek of San Francisco, California, another volunteer, said it astonishes him how people are able to identify planets from so far away.

“It still continues to astonish me how we can detect, let alone glean so much information, about another planet thousands of light-years away just by studying the light from its parent star,” Jek said.

Image 2 (below): A family portrait of the PH1 planetary system: The newly discovered planet is depicted in this artist’s rendition transiting the larger of the two eclipsing stars it orbits. Off in the distance, well beyond the planet orbit, resides a second pair of stars bound to the planetary system. Image Credit: Haven Giguere/Yale.

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