Re-thinking an Alien World   
       
   Jan. 13, 2012: Forty light years from Earth, a rocky world named "55 Cancri e"   
   circles perilously close to a stellar inferno.  Completing one orbit in only   
   18 hours, the alien planet is 26 times closer to its parent star than Mercury   
   is to the Sun. If Earth were in the same position, the soil beneath our feet   
   would heat up to about 3200 F.  Researchers have long thought that 55 Cancri e   
   must be a wasteland of parched rock.   
       
   Now they're thinking again.  New observations by NASA's Spitzer Space   
   Telescope suggest that 55 Cancri e may be wetter and weirder than anyone   
   imagined.   
       
   http://www.youtube.com/watch?v=H_CZCmJ2om0   
       
   An artist's concept of Earth and 55 Cancri e positioned side by side for   
   comparison. [video]   
   Spitzer recently measured the extraordinarily small amount of light 55 Cancri   
   e blocks when it crosses in front of its star. These transits occur every 18   
   hours, giving researchers repeated opportunities to gather the data they need   
   to estimate the width, volume and density of the planet.   
       
   According to the new observations, 55 Cancri e has a mass 7.8 times and a   
   radius just over twice that of Earth. Those properties place 55 Cancri e in   
   the "super-Earth" class of exoplanets, a few dozen of which have been found.   
   Only a handful of known super-Earths, however, cross the face of their stars   
   as viewed from our vantage point in the cosmos, so 55 Cancri e is better   
   understood than most.   
       
   When 55 Cancri e was discovered in 2004, initial estimates of its size and   
   mass were consistent with a dense planet of solid rock.  Spitzer data suggest   
   otherwise: About a fifth of the planet's mass must be made of light elements   
   and compounds--including water. Given the intense heat and high pressure these   
   materials likely experience, researchers think the compounds likely exist in a   
   "supercritical" fluid state.   
       
   A supercritical fluid is a high-pressure, high-temperature state of matter   
   best described as a liquid-like gas, and a marvelous solvent. Water becomes   
   supercritical in some steam turbines--and it tends to dissolve the tips of the   
   turbine blades. Supercritical carbon dioxide is used to remove caffeine from   
   coffee beans, and sometimes to dry-clean clothes. Liquid-fueled rocket   
   propellant is also supercritical when it emerges from the tail of a spaceship.   
       
   On 55 Cancri e, this stuff may be literally oozing--or is it steaming?--out of   
   the rocks.   
       
   With supercritical solvents rising from the planet's surface, a star of   
   terrifying proportions filling much of the daytime sky, and whole years   
   rushing past in a matter of hours, 55 Cancri e teaches a valuable lesson: Just   
   because a planet is similar in size to Earth does not mean the planet is like   
   Earth.   
       
   It's something to re-think about.   
       
       
   Author:Dr. Tony Phillips| Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
   More Information   
       
   Credits: The original research reported in this story has been accepted for   
   publication in Astronomy and Astrophysics.  The lead author is Brice-Olivier   
   Demory, a post-doctoral associate in Professor Sara Seager's group at MIT.   
       
   Spitzer Space Telescope -- home page   
       
   Kepler Discovers a Tiny Solar System -- Science@NASA   
       
   Kepler Discovers Three "Hot Earths" -- Science@NASA   
       
   Kepler Confirms Exo-Planets in the "Goldilocks Zone" -- Science@NASA   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.72   
    * Origin: NCS BBS (1:3828/7)