Scientists from NASA and San Diego State University found the largest planet orbiting two stars. They call it Kepler-1647b, a 4.4 billion-year-old, nearly Jupiter-sized planet located 3,700 light-years away from us.

Kepler-1647b is too faint to be seen with the naked eye but it is the biggest transiting circumbinary planet discovered as told by scientists during the American Astronomical Society meeting in San Diego today. Planets orbiting two stars, termed circumbinary planets like Kepler-1647b, are also known as Tatooine, named after Luke Skywalker’s home.

“It’s a bit curious that this biggest planet took so long to confirm since it is easier to find big planets than small ones,” adds the study’s co-author Jerome Orosz, an astronomer at San Diego State University. “But it is because its orbital period is so long.”


Artist’s impression of the simultaneous stellar eclipse and planetary transit events on Kepler-1647 b. Such a double eclipse event is known as a syzygy. Credit: Lynette Cook

Its orbital period is around three years or 1,107 days. This makes it the longest orbiting period of any currently known exoplanet. Unlike other circumbinary planets, Kepler-1647b is situated further away from its stars, putting it in a habitable zone that makes it favorable to sustaining life.

Nevertheless, Kepler-1647b is a gas giant like Jupiter, which makes it incapable of sustaining life. Still, if further investigations reveal that it has large moons, it could be a good candidate to support life instead.

“Habitability aside, Kepler-1647b is important because it is the tip of the iceberg of a theoretically predicted population of large, long-period circumbinary planets,” says co-author William Welsh, also an astronomer at SDSU.

Finding the new planet involved analyzing its star’s light, which was first noticed by study co-author Laurance Doyle, an astronomer at SETI Institute. However, confirming Kepler-1647b’s status as a circumbinary planet was complicated due to its inconsistency in the duration and depth of its transits, which were also irregularly spaced in time.

The study will be published in the Astrophysical Journal.