Program planet hunters reveal new planet with unusual planetary motion

Scientists have confirmed that a low-mass, low-density planet called PH3c has a highly inconsistent orbit time around its sun.

The new planet is said to be located 2,300 light years from Earth and has an atmosphere loaded with hydrogen and helium. The elusive orb nearly avoided detection. This is because PH3c has a different orbit time around sun, due to the gravitational influence of other planets in its system.

Yale graduate student and first author of the paper, Joseph Schmitt, said that PH3c's orbital period changed by 10.5 hours in just 10 orbits.

That inconsistency kept it from being picked up by automated computer algorithms that search stellar light curves and identify regular dips caused by objects passing in front of stars.

The program Planet Hunters, which has found more than 60 planet candidates since 2010 has enlisted citizen scientists to check survey data from the Kepler spacecraft. Planet Hunters recently unveiled a new website and an expanded scientific mission.

Not only has Planet Hunters spotted PH3c, but the discovery has also enabled astronomers to better characterize two other planets, one on each side of PH3c.

Schmitt has said that the middle planet was key to confirming the others and allowing us to find their masses and outer planet's orbital period has also changed slightly, by about 10 minutes.

The study is published in the journal The Astrophysical Journal.