NASA'S Kepler Discovery Confirms First Planet Orbiting Two Stars

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Sept. 15, 2011

NASA's Kepler mission has turned fiction into fact. A world with a double sunset that was first imagined in Star Wars over 30 years ago in a galaxy far, far away has become scientific reality. NASA's Kepler mission has made the first unambiguous detection of a circumbinary planet -- a planet orbiting, not one, but two stars -- 200 light-years from Earth.

The planet is cold and gaseous unlike Star Wars' Tatooine and is not thought to harbor life, but its discovery demonstrates the diversity of planets in our solar system.

Unequivocal evidence for the existence of a circumbinary planet has been limited, until now. Hints of their existence have been presented, but clear confirmation has been elusive. Kepler detected the planet through what is known as a planetary transit -- an event where the brightness of a star dims as a result of a planet crossing in front of it.

Image above: In the Light of Two Suns - This artist's concept illustrates Kepler-16b, the first planet known to definitively orbit two stars -- what's called a circumbinary planet. The planet, which can be seen in the foreground, was discovered by NASA's Kepler mission. Image credit: NASA / JPL-Caltech / T. Pyle.

"This discovery provides confirmation of a new class of planetary systems that could harbor life. Given that most stars in our galaxy are part of a binary system, this means that the opportunities for life are much broader than if planets form only around single stars," said Kepler principal investigator William Borucki. "This milestone discovery confirms a theory that scientists have had for decades but could not be proven until now."

A research team, led by Laurance Doyle of the SETI Institute, used data from the Kepler space telescope, which measures dips in the brightness of more than 150,000 stars, to search for transiting planets. Kepler is the first NASA mission capable of finding Earth-size planets in or near the "habitable zone," the region in a planetary system where liquid water can exist on the surface of the orbiting planet. This finding provides significant insight into the world of planetary formation.

"Theorists have been debating for years about whether giant planets could form around close binary star systems- some said yes, others said no," said theoretical astrophysicist Alan Boss of the Carnegie Institution of Washington. "Kepler has now answered this question with a resounding 'YES'!"

Image: Where the Sun Sets Twice - NASA's Kepler mission has discovered a world where two suns set over the horizon instead of just one. The planet, called Kepler-16b, is the most "Tatooine-like" planet yet found in our galaxy. Tatooine is the name of Luke Skywalker's home world in the science fiction movie Star Wars. In this case, the planet it not thought to be habitable. It is a cold world, with a gaseous surface, but like Tatooine, it circles two stars. Image credit: NASA / JPL-Caltech / R. Hurt.

This discovery confirms that Kepler-16b is an inhospitable, cold world about the size of Saturn, and thought to be made up of about half rock and half gas. The parent stars are both smaller than our sun; one is 69 percent and the other only 20 percent the mass of the sun. Kepler-16b orbits around both stars every 229 days, similar to Venus’ 225-day orbit, but lies outside the system's habitable zone, where liquid water could exist on the surface, because the stars are cooler than our sun.

Animation: Three Eclipsing Bodies - This artist's movie illustrates Kepler-16b, the first directly detected circumbinary planet, which is a planet that orbits two stars. The movie begins by showing the gaseous surface of the rotating planet then pans out to show the stars it orbits. Image credit: NASA / JPL-Caltech / T. Pyle.

"Working in film, we are often tasked with creating something never before seen," said visual effects supervisor John Knoll of Industrial Light & Magic. "However, more often than not, scientific discoveries prove to be more spectacular than anything we dare imagine. There is no doubt these discoveries influence and inspire storytellers. Their very existence serves as cause to dream bigger, to open our mind to new possibilities beyond what we think we 'know'."

Animation: A Dance of Two Suns and One Planet - This artist's animation illustrates the Kepler-16 system from an overhead view, showing the eccentric orbits of the two stars as they twirl around each other every 41 days like figure skaters. The planet, which was discovered by NASA's Kepler mission, orbits in a circle around both of the stars every 229 days. The larger of the stars is about 69 percent of the mass of the sun, and the smaller is about 20 percent of the sun's mass. The planet is about the mass of Saturn. All three bodies orbit in the same plane, which is why Kepler can observe the various planetary and stellar eclipses.
Image credit: NASA / JPL-Caltech / T. Pyle.

For more information about the Kepler-16 discovery, visit: http://kepler.nasa.gov/Mission/discoveries/kepler16b/

For more information about NASA’s Kepler Mission, visit: http://www.nasa.gov/kepler

For more information about NASA’s Ames Research Center, visit: http://www.nasa.gov/ames

Images (mentioned), Videos (mentioned), Text, Credit: NASA / JPL-Caltech.

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