NASA'S Kepler Discovery Confirms First Planet Orbiting Two Stars

[NASA News <hqnews@xxxxxxxxxxxxxxxxxxxxxx>]

Sept. 15, 2011

Trent J. Perrotto 
Headquarters, Washington                                    
202-358-0321 
trent.j.perrotto@xxxxxxxx 

Michele Johnson 
Ames Research Center, Moffett Field, Calif.                          
650-604-4789 
michele.johnson@xxxxxxxx 



RELEASE: 11-304

NASA'S KEPLER DISCOVERY CONFIRMS FIRST PLANET ORBITING TWO STARS

WASHINGTON -- The existence of a world with a double sunset, as 
portrayed in the film Star Wars more than 30 years ago, is now 
scientific fact. NASA's Kepler mission has made the first unambiguous 
detection of a circumbinary planet -- a planet orbiting two stars -- 
200 light-years from Earth. 

Unlike Star Wars' Tatooine, the planet is cold, gaseous and not 
thought to harbor life, but its discovery demonstrates the diversity 
of planets in our galaxy. Previous research has hinted at the 
existence of circumbinary planets, but clear confirmation proved 
elusive. Kepler detected such a planet, known as Kepler-16b, by 
observing transits, where the brightness of a parent star dims from 
the planet crossing in front of it. 
"This discovery confirms a new class of planetary systems that could 
harbor life," Kepler principal investigator William Borucki said. 
"Given that most stars in our galaxy are part of a binary system, 
this means the opportunities for life are much broader than if 
planets form only around single stars. This milestone discovery 
confirms a theory that scientists have had for decades but could not 
prove until now." 

A research team led by Laurance Doyle of the SETI Institute in 
Mountain View, Calif., 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. 

Scientists detected the new planet in the Kepler-16 system, a pair of 
orbiting stars that eclipse each other from our vantage point on 
Earth. When the smaller star partially blocks the larger star, a 
primary eclipse occurs, and a secondary eclipse occurs when the 
smaller star is occulted, or completely blocked, by the larger star. 

Astronomers further observed that the brightness of the system dipped 
even when the stars were not eclipsing one another, hinting at a 
third body. The additional dimming in brightness events, called the 
tertiary and quaternary eclipses, reappeared at irregular intervals 
of time, indicating the stars were in different positions in their 
orbit each time the third body passed. This showed the third body was 
circling, not just one, but both stars, in a wide circumbinary orbit. 


The gravitational tug on the stars, measured by changes in their 
eclipse times, was a good indicator of the mass of the third body. 
Only a very slight gravitational pull was detected, one that only 
could be caused by a small mass. The findings are described in a new 
study published Friday, Sept. 16, in the journal Science. 

"Most of what we know about the sizes of stars comes from such 
eclipsing binary systems, and most of what we know about the size of 
planets comes from transits," said Doyle, who also is the lead author 
and a Kepler participating scientist. "Kepler-16 combines the best of 
both worlds, with stellar eclipses and planetary transits in one 
system." 

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 smaller than our sun. One is 69 
percent the mass of the sun and the other only 20 percent. 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. 

"Working in film, we often are tasked with creating something never 
before seen," said visual effects supervisor John Knoll of Industrial 
Light & Magic, a division of Lucasfilm Ltd., in San Francisco. 
"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 and open our minds to new 
possibilities beyond what we think we 'know.'" 

For more information about the Kepler mission and to view the digital 
press kit, visit: 



http://www.nasa.gov/kepler 

	
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