Kepler Confirms First Planet in Habitable Zone of Sun-like Star   
       
   Dec 5, 2011:  NASA's Kepler mission has confirmed its first planet in the   
   "habitable zone" of a distant sun-like star.   
       
   This artist's conception illustrates Kepler-22b, a planet known to comfortably   
   circle in the habitable zone of a sun-like star. [larger image]   
   The newly confirmed planet, Kepler-22b, is about 2.4 times the radius of   
   Earth. Scientists don't yet know if Kepler-22b has a predominantly rocky,   
   gaseous or liquid composition, but its discovery is a step closer to finding   
   Earth-like planets1.   
       
   The "habitable zone" of a planetary system refers to the band of orbits where   
   liquid water could exist on a planet's surface. Kepler has recently discovered   
   more than 1,000 new planet candidates. Ten of these candidates are   
   near-Earth-size and orbit in the habitable zone of their host star. Candidates   
   require follow-up observations to verify they are actual planets.   
       
   "This is a major milestone on the road to finding Earth's twin," said Douglas   
   Hudgins, Kepler program scientist at NASA Headquarters in Washington.   
   Kepler-22b is located 600 light-years away. While the planet is larger than   
   Earth, its orbit of 290 days around a sun-like star resembles that of our   
   world. The planet's host star belongs to the same class as our sun, called   
   G-type, although it is slightly smaller and cooler.   
       
   Kepler discovers planets and planet candidates by measuring dips in the   
   brightness of more than 150,000 stars to search for planets that cross in   
   front, or "transit," the stars. Kepler requires at least three transits to   
   verify a signal as a planet.   
       
   "Fortune smiled upon us with the detection of this planet," said William   
   Borucki, Kepler principal investigator at NASA Ames Research Center at Moffett   
   Field, Calif., who led the team that discovered Kepler-22b. "The first transit   
   was captured just three days after we declared the spacecraft operationally   
   ready. We witnessed the defining third transit over the 2010 holiday season."   
       
   http://www.nasa.gov/mission_pages/kepler/multimedia/images/kepler-22b-diagram   
   .html   
       
   This diagram compares our own solar system to Kepler-22, a star system   
   containing the first "habitable zone" planet discovered by NASA's Kepler   
   mission. The habitable zone is the sweet spot around a star where temperatures   
   are right for water to exist in its liquid form. Liquid water is essential for   
   life on Earth. [more]   
       
   The Kepler science team uses ground-based telescopes and the Spitzer Space   
   Telescope to review observations on planet candidates the spacecraft finds.   
   The star field that Kepler observes in the constellations Cygnus and Lyra can   
   only be seen from ground-based observatories in spring through early fall. The   
   data from these other observations help determine which candidates can be   
   validated as planets.   
       
   Of the 54 habitable zone planet candidates reported in February 2011,   
   Kepler-22b is the first to be confirmed. This milestone will be published in   
   The Astrophysical Journal.   
       
   The Kepler team is hosting its inaugural science conference at Ames Dec. 5-9,   
   announcing 1,094 new planet candidate discoveries. Since the last catalog was   
   released in February, the number of planet candidates identified by Kepler has   
   increased by 89 percent and now totals 2,326. Of these, 207 are approximately   
   Earth-size, 680 are super Earth-size, 1,181 are Neptune-size, 203 are   
   Jupiter-size and 55 are larger than Jupiter.   
       
   The findings, based on observations conducted May 2009 to September 2010, show   
   a dramatic increase in the numbers of smaller-size planet candidates.   
   Earth-size and super Earth-size candidates have increased in number by more   
   than 200 and 140 percent since February, respectively. These new data suggest   
   that planets one to four times the size of Earth may be abundant in the galaxy.   
   So far, there are 48 planet candidates in their star's habitable zone. While   
   this is a decrease from the 54 reported in February, the Kepler team has   
   applied a stricter definition of what constitutes a habitable zone in the new   
   catalog, to account for the warming effect of atmospheres, which would move   
   the zone away from the star, out to longer orbital periods.   
       
   "The tremendous growth in the number of Earth-size candidates tells us that   
   we're honing in on the planets Kepler was designed to detect: those that are   
   not only Earth-size, but also are potentially habitable," said Natalie   
   Batalha, Kepler deputy science team lead at San Jose State University in San   
   Jose, Calif.   
       
   Production Editor: Dr. Tony Phillips | Credit: Science@NASA   
   More Information   
       
   NASA's Kepler Mission   
   Kepler Science Conference News Briefing Press Kit   
   Footnote: (1) Previous research hinted at the existence of near-Earth-size   
   planets in habitable zones, but clear confirmation proved elusive. Two other   
   small planets orbiting stars smaller and cooler than our sun recently were   
   confirmed on the very edges of the habitable zone, with orbits more closely   
   resembling those of Venus and Mars.   
       
   Credits:  NASA's Ames Research Center manages Kepler's ground system   
   development, mission operations and science data analysis. NASA's Jet   
   Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development.   
   Ball Aerospace and Technologies Corp. in Boulder, Colo., developed the Kepler   
   flight system and supports mission operations with the Laboratory for   
   Atmospheric and Space Physics at the University of Colorado in Boulder. The   
   Space Telescope Science Institute in Baltimore archives, hosts and distributes   
   the Kepler science data. Kepler is NASA's 10th Discovery Mission and is funded   
   by NASA's Science Mission Directorate at the agency's headquarters.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.64   
    * Origin: NCS BBS (1:3828/7)