The citizen-science project planethunters.org has reported the discovery of a new circumbinary exoplanet, designated Planet Hunters 1 (PH1).

PH1 orbits an eclipsing binary, KIC 4862625 (AB), which is located 4,892 light years from Earth. KIC 4862625 (A) is a yellow class-F star, 1.7 times the mass of the Sun. KIC 4862625 (B) is an M-class red dwarf star, 0.4 times the mass the Sun. The two stars circle each other once every 20 days.

Ph1 has a diameter of 47,600-50,300 miles, about midway in size between Uranus and Saturn. The mass of the planet has been determined to be no more than 169 times the mass of the Earth.

Ph1 orbits the binary star once every 138.5 days at an average distance of 0.634 AU. The habitable zone of the system has been determined to begin at 2.98 AU, so PH-1b is too warm to support life as we know it.

The planet was discovered by citizen scientists analyzing light curves from NASA’s Kepler space telescope. The Planet Hunters website provides Kepler data to citizen scientists who use human pattern recognition to identify light changes due to transiting exoplanets.

In addition to the planet, a second, previously unknown binary star has been discovered, orbiting KIC 4862625 (AB) at a distance of approximately 1000 AU.