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Penn State Astronomers Measure Binary Star System

A team of researchers from Penn State University has made precise measurements of a binary star system 200 light-years away.

The Kepler-16 system was discovered in 2011 by a team from NASA, but the Penn State study is the first to discern the light output from each of the two small stars using a spectrograph.

The binary star system is one of a handful of its kind in the known universe because a planet orbits both suns, according to Penn State astronomer and lead author Dr. Chad Bender. He said precise measurements of these rare systems help astrophysicists winnow down the theories on exactly how solar systems are formed from gas nebulas.

"[The theories] don't work perfectly," said Bender. "There's still some loose ends to tie up, I guess. Some things are unclear, exactly how all those steps occur. When you have two stars and a planet forming around them, the situation is even more complicated."

If the theorists' models don't measure up to the new data gathered by Bender's team, the astrophysics community tosses those ideas.

Bender's team worked with astronomers at McDonald Observatory in Texas to break down the total light output from the Kepler-16 system. Bender said the group could differentiate between the light of each star by examining a variety of wavelengths with a spectrograph.

"It's like taking a prism and putting it in front of sunlight, and spreading it out onto your kitchen table like a rainbow," said Bender. He said each star of Kepler-16 absorbs some parts of the other's light output. "For example, iron absorbs light at certain wavelengths, so if you look at a spectrum, you'll see the light at the wavelengths iron absorbs will be missing."

The larger star of the system is about 70% the mass of our sun, while the smaller of the two dwarfs is about one-fifth of a solar mass. Bender said the planet that orbits both stars is a large, gaseous world in the vein of Neptune.

The Kepler-16 data is the initial result of a much larger Penn State project to measure about 100 binary star systems discovered by NASA's Kepler spacecraft.

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