Exciting Kepler News – Part 2: New Circumbinary Planets

 There were two exciting Kepler (the NASA mission tasked with discovering planets outside of our solar system) news released yesterday. I’m covering them in two separate posts. This is Part 2; read Part 1.

The second exciting Kepler news release is one of the most interesting yet; in fact, this discovery confirmed the existence of an entirely new class of planetary system! Today, astronomers announced the discovery of two new “circumbinary” planet systems; these follow the first circumbinary planet system announced in September of last year, the planet Kepler-16b.

So what does circumbinary mean anyway, and why is it so interesting? Let me answer the first question, which should preclude the need to answer the second.

Scene from Star Wars Episode IV: A New Hope, showing binary stars from Tatooine.
Classic scene from Star Wars Episode IV: A New Hope, showing a dual sunset from the circumbinary planet, Tatooine.

A circumbinary planet is one that orbits not one, but two stars. When Kepler-16b was confirmed last Fall, it wasn’t clear whether we should expect many more circumbinary planets or if that system was just a fluke. With the discovery of these two new systems, it is becoming apparent that circumbinary planets are abundant.

What makes this interesting is that binary-star systems are abundant in our galaxy. From the report published in Nature:

The observed rate of circumbinary planets in our sample implies that more than ~1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.

At least several million!

As for the planets themselves, they are both gas giants about the size of Saturn.  Kepler-34b orbits its binary-pair of Sun-like stars every 289 days, while the stars themselves orbit and eclipse each other every 28 days. Kepler-35b orbits its smaller pair of stars every 131 days, with the stars orbiting and eclipsing one another every 21 days.  The Kepler-34 and Kepler-35 systems lie in the constellation Cygnus, 4,900 and 5,400 light-years from Earth, respectively.


For more information, check out these links:

NASA Kepler News Release

The paper, published in Nature

The news release for Kepler-16b, the first circumbinary planet discovered