Kepler Discovers Multiple Planets Transiting a Single   
       
   August 26, 2010:  NASA's Kepler spacecraft has discovered the first confirmed   
   planetary system with more than one planet crossing in front of, or   
   transiting, the same star.   
       
   The transit signatures of two distinct Saturn-sized planets were seen in the   
   data for a sun-like star designated "Kepler-9." The planets were named   
   Kepler-9b and 9c. The discovery incorporates seven months of observations of   
   more than 156,000 stars as part of an ongoing search for Earth-sized planets   
   outside our solar system. The findings will be published in Thursday's issue   
   of the journal Science.   
       
   Kepler's ultra-precise camera measures tiny decreases in the stars' brightness   
   that occur when a planet transits them. The size of the planet can be derived   
   from these temporary dips.   
   [...]   
   An artist's concept of two Saturn-sized planets in the Kepler-9 planetary   
   system. [larger image]   
       
   The distance of the planet from the star can be calculated by measuring the   
   time between successive dips as the planet orbits the star. Small variations   
   in the regularity of these dips can be used to determine the masses of planets   
   and detect other non-transiting planets in the system.   
       
   In June, mission scientists submitted findings for peer review that identified   
   more than 700 planet candidates in the first 43 days of Kepler data. The data   
   included five additional candidate systems that appear to exhibit more than   
   one transiting planet. The Kepler team recently identified a sixth target   
   exhibiting multiple transits and accumulated enough follow-up data to confirm   
   this multi-planet system.   
       
   "Kepler's high quality data and round-the-clock coverage of transiting objects   
   enable a whole host of unique measurements to be made of the parent stars and   
   their planetary systems," said Doug Hudgins, the Kepler program scientist at   
   NASA Headquarters in Washington DC.   
   [...]   
   Click on the image to view animations of the Kepler-9 planetary system.     
   Scientists refined the estimates of the masses of the planets using   
   observations from the W.M. Keck Observatory in Hawaii. The observations show   
   Kepler-9b is the larger of the two planets, and both have masses similar to   
   but less than Saturn. Kepler-9b lies closest to the star with an orbit of   
   about 19 days, while Kepler-9c has an orbit of about 38 days. By observing   
   several transits by each planet over the seven months of data, the time   
   between successive transits could be analyzed.   
       
   "This discovery is the first clear detection of significant changes in the   
   intervals from one planetary transit to the next, what we call transit timing   
   variations," said Matthew Holman, a Kepler mission scientist from the   
   Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "This is   
   evidence of the gravitational interaction between the two planets as seen by   
   the Kepler spacecraft."   
       
   In addition to the two confirmed giant planets, Kepler scientists also have   
   identified what appears to be a third, much smaller transit signature in the   
   observations of Kepler-9. That signature is consistent with the transits of a   
   super-Earth-sized planet about 1.5 times the radius of Earth in a scorching,   
   near-sun 1.6 day-orbit. Additional observations are required to determine   
   whether this signal is indeed a planet or an astronomical phenomenon that   
   mimics the appearance of a transit.   
       
   For more information about the Kepler mission, visit http://www.   
   asa.gov/kepler.   
       
       
   Editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   NASA's Ames Research Center in Moffett Field, Calif., 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.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.54   
    * Origin: NCS BBS (1:3828/7)