kepler 1647b two suns Lynette Cook

Located about 3,700 light-years away, in the direction of the Cygnus constellation, lies a distant planet called Kepler-1647b, which at approximately 4.4 billion years of age is roughly as old as Earth.

But that's about where the similarities end, because Kepler-1647b turns out to hold a pretty sensational point of difference: this newly identified world is the largest planet ever discovered that orbits two stars. Known as circumbinary planets, these strange cosmic phenomena are often called "Tatooine" planets, after Luke Skywalker's dusty desert home.

An international team of astronomers led by NASA's Goddard Space Flight Centre just announced the discovery of Kepler-1647b, which has a mass and radius that are nearly identical to Jupiter's. But just because this circumbinary planet might be the largest of its kind that we currently know about, that didn't make locating it any easier.


The team identified the planet using data recorded by the Kepler space observatory, and adding to the challenge was Kepler-1647b's other remarkable feature – the immense length of its orbital period. At 1,107 days, this is the longest of any confirmed transiting exoplanet astronomers have yet found.

This means it takes over three years for Kepler-1647b to orbit its host stars - both of which are similar in size to our Sun, with one being slightly smaller, and the other being slightly larger.

That epic orbital period is the result of Kepler-1647b being located further away from its host stars than other circumbinary planets, which usually hold relatively tight orbits.

In the image below, you can see just how much wider Kepler-1647b's orbit (in red) is compared to its circumbinary counterparts (in grey), with Earth's orbit (in blue) added in for reference.

kepler 1647b orbit B. Quarles



kepler planet comparison size Lynette Cook


But, in this case, since Kepler-1647b is a gas giant like Jupiter, the researchers think it's unlikely to host life – although there's a possibility any as-yet-undiscovered moons orbiting the planet could provide a suitable environment for it.


kepler 1647b planet Lynette Cook

But just because we probably won't find alien life on Kepler-1647b doesn't mean the planet isn't a major find. In addition to its record-breaking size and orbital length, the scientists think this Tatooine-esque planet could herald the discovery of a new generation of similar worlds that have eluded us until now.

When you consider that the first such planet – Kepler-16b – was only discovered five years ago, it becomes clear why this is such an exciting time for astronomy. Kepler-1647b is the 11th confirmed circumbinary planet discovered by the Kepler telescope since then.


The findings have been accepted for publication in The Astrophysical Journal.