Planets Around Binary Stars Are Common

Millions of such systems possibly exist in the galaxy

By on January 12th, 2012 10:06 GMT

Circumbinary planet systems (CBPS) are made up of one or more planets orbiting a binary star system. Until now, these were believed to be very rare, but recent discoveries from the NASA Kepler Telescope appear to indicate that millions of such systems may exist in our galaxy alone.

The planet-hunting telescope was able to discover two new CBPS, bringing the total known number of such structures to three. For studies conducted in space, this is a very high number, which implies that other binary stars may also have planets around them, but we're unable to observe them right now.

Our techniques for searching exoplanets are not that well developed at this point, which may help explain why we are having such a hard time discovering more of these worlds. However, one of the main obstacles to this type of search was purely theoretical.

That is to say, astronomers believed that the chances of such planets remaining in stable orbits around two stars were every slim. Now that practical observations proved them wrong, they are bound to turn their attention more and more towards these worlds.

“Once again, we're seeing science fact catching up with science fiction,” explains Harvard-Smithsonian Center for Astrophysics (CfA) astronomer and study coauthor Josh Carter. Details of the work appear in the latest online issue of the top scientific journal Nature.

The study was also presented at the annual meeting of the American Astronomical Society (AAS2012), which was held in Austin, Texas. The presentation was held by lead study author William Welsh, who is based at the San Diego State University (SDSU).

Scientists named the two new exoplanets Kepler-34b and Kepler-35b, respectively. Both are gas giants about the size of Saturn, and orbit their parent stars in 289 and 131 days, respectively. The stars in Kepler-34 orbit each other in 28 days, while those in Kepler-35 take about 21 days to do so.

These systems are located relatively close to Earth and to each other, in the constellation Cygnus (the Swan). Kepler-34 lies some 4,900 light-years away, while Kepler-35 is only 5,400 light-years away. This practically puts them in our cosmic backyard.

One of the least-explored aspects of CBPS is the effects binary stars have on their planets' climates. “It would be like cycling through all four seasons many times per year, with huge temperature changes,” Welsh says.

“The effects of these climate swings on the atmospheric dynamics, and ultimately on the evolution of life on habitable circumbinary planets, is a fascinating topic that we are just beginning to explore,” the expert concludes.