Two new transiting “circumbinary” planet systems found

Using data from NASA’s Kepler Mission, astronomers announced the discovery of two new transiting “circumbinary” planet systems — planets that orbit two stars. This work establishes that such “two sun” planets are not rare exceptions, but are in fact common with many millions existing in our Galaxy. The work is published today in the journal Nature and presented at the American Astronomical Society meeting in Austin, TX.

Using data from NASA’s Kepler mission, a team that includes a University of Florida astronomer has discovered two new planets orbiting double star systems, something that had never been seen until last September.

The newly confirmed planets, called Kepler-34b and Kepler-35b, will be announced in Wednesday’s online edition of the journal Nature, said Eric B. Ford, UF associate professor of astronomy. William F. Welsh, associate professor at San Diego State University, is the lead author on the paper.

Kepler-34b and Kepler-35b both orbit a “binary star.” They are actually a pair of gravitationally bound stars that orbit each other. While the existence of such bodies, called “circumbinary planets,” had long been predicted, they remained just a theory until the team discovered Kepler-16b in September 2011. They dubbed Kepler-16b “Tatooine” because of its resemblance to the two-sun world depicted in the “Star Wars” film series.

“We have long believed these kinds of planets to be possible, but they have been very difficult to detect for various technical reasons,” Ford said. “With the discoveries of Kepler-16b, 34b and 35b, the Kepler mission has shown that the galaxy abounds with millions of planets orbiting two stars.”

The planets were discovered by measuring the star light decrease as the planets pass in front of, or transit, either of the two stars. Kepler also measures the star light decrease when one of the stars passes in front of the other. The mutual gravitational tugs of the stars and planets cause the times of the transits to deviate from a regular schedule, allowing astronomers to confirm the planet and measure its mass.

Both planets are low-density gas giants, comparable in size to Jupiter, but much less massive. Compared to Jupiter, Kepler-34 is about 24 percent smaller in size, but has 78 percent less mass. It can complete a full orbit in 288 terrestrial days. Kepler-35 is about 26 percent smaller, has 88 percent less mass, and completes its orbit around the stars much faster – just 131 days.

via New class of planetary systems: Astronomers find two new planets orbiting double suns.

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