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This artist's concept illustrates Kepler-16b, the first planet known to definitely orbit two stars.

Tatooine in Real Life

SDSU professors help discover the first planet to orbit a pair of stars.
By Ashley Vaughn

A tally on NASA’s website for the Kepler Mission, a search for habitable plants, lists 21 confirmed planets, 1,235 potential planets and 2,165 eclipsing binary stars. With the help of three SDSU professors, NASA can now boast that they have discovered the first circumbinary planet, Kepler-16b, a planet that orbits two stars.

Circumbinary planets were once thought to be something that could only exist in Hollywood. While they have made appearances on the big screen — like the planet Tatooine in the Star Wars series — Kepler-16 is the first real-life discovery of its kind.

“It’s hard to overstate what a great advance the Kepler Mission is,” said Professor Jerome Orosz, SDSU astronomy professor, who is a part of the team of scientists analyzing Kepler data. “Likewise, the discovery of Kepler-16 is perhaps the biggest discovery in exoplanet studies since the discovery of 51 Pegasi.”

Sun-like first

51 Pegasi, discovered in 1995, was the first Sun-like star found to have a planet orbiting it.

Orosz, along with SDSU astronomy professor William Welsh and former College of Sciences Dean Donald Short, analyzed the Kepler-16 data to determine the properties of the stars including their sizes. By observing transits, where the brightness of a star dims when a planet crosses in front of it, Kepler-16 was discovered and its radius measured. Using other telescopes, the Kepler team was able to measure the planet's mass. 

As the pair of stars orbited each other, an eclipse would occur every time the stars blocked one another. Dean Short, using a suite of software he developed, measured precise times of these eclipses, including the dip in brightness that occurred when the planet crossed in front of the stars.

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The Kepler Mission research is one of many ways SDSU faculty are leading innovation and discovery, a key initiative of the Campaign for SDSU. With a unique focus on the teacher-scholar model, SDSU attracts researchers interested in solving the world’s most pressing problems, while showing students how to provide future solutions. Learn more about how SDSU leads innovation and discovery, and how you can help.

Cold, gaseous planet

Unlike Tatooine, Kepler-16b is a cold gaseous planet just outside of the habitable zone. While the amount of sunlight we receive on Earth is constant, the amount of sunlight on Kepler-16b can vary up to 10 percent. The temperature on Kepler-16b only reaches  a cool 200 Kelvin or -100 degrees Fahrenheit.  So, don’t book your ticket just yet because you won’t find Luke Skywalker there.

However, Orosz remains hopeful that a circumbinary system with habitable planets exists.

“Kepler-16b shows us that planetary bodies can exist in circumbinary orbits. The Kepler Mission represents a huge step forward not only in planetary science, but in the study of stars,” said Orosz.

SDSU has another connection to this discovery. The full Kepler-16 paper was written by SDSU alumnus Laurance Doyle. Doyle, a researcher at the SETI Institute in Mountain View  California, earned his bachelor’s degree in astronomy in 1974 and master’s in astronomy in 1979 from SDSU.

Related Content:

SDSU helps find first planet with two suns - San Diego Union-Tribune, Oct. 24, 2011

Tatooine-like Planet Discovered by SDSU Professors -NBC San Diego, Oct. 24, 2011