UF astronomer plays a role in Kepler’s big find

By Javier Barbuzano

Using data from NASA’s Kepler mission, a team including a University of Florida astronomer has discovered two new planets orbiting distant double-star systems.

The team announced their discovery of the newly confirmed planets, Kepler-34b and Kepler-35b, at the 219th meeting of the American Astronomical Society and in the online edition of the journal Nature.

The two planets orbit a binary star — a pair of gravitationally bound stars that orbit each other. Theorists have long predicted the existence of such circumbinary planets, but none have been observed until the discovery of Kepler 16-b.

The new discoveries confirm that circumbinary planets are fairly common in our galaxy.

“We have long believed these kinds of planets to be possible, but they have been very difficult to detect for various technical reasons,” said Eric Ford, UF associate professor of astronomy.

Both planets are low-density gas giants, comparable in size to Jupiter, but with much less mass. Kepler-34 can complete a full orbit in 288 terrestrial days.

Kepler-35 completes its orbit around the stars much faster — just 131 days.

The astronomers believe the planets are made primarily of hydrogen and are too hot to sustain life.

“Circumbinary planets can have much more complex climates, since the distance between the planet and each star changes significantly during each orbital period, the length of an alien planet’s year,” Ford said. “For Kepler-35b, the amount of incoming starlight changes by over 50 percent within a single Earth- year. For Kepler-34b, each Earth-year brings ‘summers’ with 2.3 times as much starlight as winters.”

Compare that to Earth, where the amount of sunlight heating the Earth over the course of a year varies by only 6 percent, he said.

NASA’s Kepler mission, which began in March 2009, uses a 1-meter space telescope trained on one small portion of the Milky Way for several years. Astronomers analyze data from the telescope for periodic dimming that indicates a planet crossing in front of its host star. The mission’s goal is to find the frequency of Earth-size planets in the habitable zone of their host stars — where a planet might have liquid water on its surface.

Most Sun-like stars in the galaxy are not alone, like the Earth’s sun, but have a “dance partner,” forming a binary system or binary star. Kepler has already identified about 2,165 eclipsing binaries, of the more than 160,000 stars being observed.

NASA originally planned to stop receiving data from the Kepler spacecraft in November 2012, but astronomers are practically begging NASA to extend the mission, Ford said.

“Kepler is revolutionizing so many fields, not just planetary science,” he said. “It would be a shame not to maximize the scientific return of this great observatory.

Eric Ford, eford@astro.ufl.edu