Weird Planets   
      
   Sept. 12, 2012: News flash: The Milky Way galaxy just got a little weirder.   
      
   Back in 2011 astronomers were amazed when NASA's Kepler spacecraft discovered   
   a planet orbiting a double star system.  Such a world, they realized, would   
   have double sunsets and sunrises just like the fictional planet Tatooine in   
   the movie Star Wars.  Yet this planet was real.   
       
   Now Kepler has discovered a whole system of planets orbiting a double star.   
       
   http://www.youtube.com/watch?v=Cl5EknhEsSQ   
       
   A new ScienceCast video takes viewers on a tour through the Kepler-47 system.   
   Play it   
       
   The star system, known as Kepler-47, is located 4,900 light-years from Earth   
   in the constellation Cygnus. Two stars orbit one another at the center of the   
   system: One is similar to the sun in size, but only 84 percent as bright. The   
   second star is smaller, only one-third the size of the sun and less than 1   
   percent as bright. Kepler found two planets orbiting this mismatched pair.   
       
   "The presence of a full-fledged planetary system orbiting Kepler-47 is an   
   amazing discovery," says Greg Laughlin, professor of Astrophysics and   
   Planetary Science at the University of California in Santa Cruz. "This is   
   going to change the way we think about the formation of planets."   
       
   The inner planet, Kepler-47b, closely circles the pair of stars, completing   
   each orbit in less than 50 days. Astronomers think it is a sweltering world,   
   where the destruction of methane in its super-heated atmosphere might lead to   
   a thick global haze.  Kepler-47b is about three times the size of Earth.   
       
   The outer planet, Kepler-47c, orbits every 303 days.  This puts it in the   
   system's habitable zone, a band of orbits that are "just right" for liquid   
   water to exist on the surface of a planet. But does this planet even have a   
   surface? Possibly not.  The astronomers think it is a gas giant slightly   
   larger than Neptune.   
       
   The discovery of planets orbiting double stars means that planetary systems   
   are even weirder and more abundant than previously thought.   
      
   http://tinyurl.com/8jz8k2e   
      
   This diagram compares our own solar system to Kepler-47, a double-star system   
   containing two planets, one orbiting in the so-called "habitable zone."   
   Credit: NASA/JPL-Caltech/T. Pyle more"Many stars are part of multiple-star   
   systems where two or more stars orbit one another. The question always has   
   been -- do they have planets and planetary systems?" says William Borucki,   
   Kepler mission principal investigator at NASA's Ames Research Center. "This   
   Kepler discovery proves that they do."   
       
   Our own sun is a single, isolated star, with a relatively simple gravitational   
   field that rules the motions of the planets orbiting it.   
       
   But, as Borucki points out, not all stars are single.  Astronomers estimate   
   that more than half of the stars in the galaxy have companions.  There are   
   double, triple and even quadruple star systems.  Any planets in such systems   
   would have to navigate a complex gravitational field, tugged in multiple   
   directions by multiple stars.  In fact, for many years, astronomers doubted   
   that planets could even form in such an environment.   
       
   Kepler-47 erases those doubts-and poses a conundrum: "These planets are very   
   difficult to form using the currently accepted paradigm," says Laughlin. "I   
   believe that theorists, myself included, will be going back to the drawing   
   board to try to improve our understanding of how planets are assembled in the   
   dusty gaseous disks that surround many young stars."   
       
   The Kepler spacecraft is on a mission to find Earth-like planets that might   
   support life.  Says Borucki: "In our search for habitable worlds, we have just   
   found more opportunities for life to exist."   
       
       
   Author: Dr. Tony Phillips| Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.82   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)