The Strange Attraction of Hot Jupiters   
       
   August 17, 2013:  When the Space Age began, astronomers knew of exactly zero   
   planets outside the solar system.  What a difference 50 years makes.   
       
   http://kepler.nasa.gov/   
       
   An artist's concept of NASA's Kepler spacecraft.   
       
   Modern, ground-based telescopes and NASA's Kepler spacecraft have now   
   confirmed more than 850 exoplanets, while thousands more await confirmation.   
   The pace of discovery suggests "there are at least 100 billion planets in our   
   galaxy," says John Johnson of Caltech, who works with data from the Kepler   
   mission. "That's mind-boggling."   
       
   When the hunt for exoplanets began, the focus was on Earth-like worlds,   
   planets like our own that might support alien life in distant solar systems.   
   Yet planets as small as Earth are difficult to detect when they circle stars   
   hundreds of light years away.  Indeed, only a handful have been found so far.   
       
   The real haul has been in gas giants, especially "hot Jupiters."  These are   
   behemoth worlds that orbit close to their parent stars, blocking a fraction of   
   the star's light when it transits in front. Observations of hot Jupiter   
   "mini-eclipses" have yielded hundreds of discoveries.   
       
   At first considered to be the "chaff" researchers would have to wade through   
   to get to the fainter Earth-like worlds, hot Jupiters are now attracting their   
   own attention.   
       
   Consider the case of "HD189733b," discovered in 2005 by a team working at the   
   Haute-Provence Observatory in France.  Because it is nearby, only 63 light   
   years away, and because it blocks a whopping 3% of the light from its   
   orange-dwarf parent star, astronomers are rapidly learning a great deal.   
       
   http://www.youtube.com/watch?v=EmsYCbYu-LA   
       
   A new ScienceCast video explores the unexpected and exotic characteristics of   
   hot Jupiters. Play it   
       
   For one thing, it's blue.  Data obtained by the Hubble Space Telescope suggest   
   that, seen from a distance, the azure disk of HD 189733b would look to the   
   human eye much like Earth.  Indeed, some members of the media have taken to   
   calling it "the other blue planet."   
       
   It is, however, anything but Earthlike.   
       
   In 2007, Heather Knutson of Caltech made a global temperature map of HD189733b   
   using NASA's infrared Spitzer Space Telescope. She knew it would be hot   
   because HD189733b orbits its star 13 times closer than Mercury. "Even so, we   
   were impressed by the readings," she recalls. Temperatures ranged from 1200 F   
   on the nightside to 1700 F on the dayside.  Thermal gradients drive winds as   
   fast as 6000 mph, carrying suffocating heat around the globe.   
       
   The blue color may be caused by silicate particles in the planet's atmosphere,   
   which scatter blue wavelengths of light from the parent star. The same physics   
   plays out in Earth's atmosphere, although the chemicals are different.   
   Silicates are a component of glass, so some researchers have speculated that   
   it is actually raining molten glass on HD189733b.   
       
   The newest observations come from a pair of X-ray observatories. NASA's   
   Chandra and the ESA's XMM Newton watched HD189733b transit its star and   
   detected a drop in X-rays three times deeper than the corresponding decrease   
   in optical light. This means the outer atmosphere is larger than anyone   
   expected.   
       
   In fact, it is probably boiling away. Authors of the study estimate HD189733b   
   is losing 100 million to 600 million kilograms of mass per second.   
       
   "The extended atmosphere of this planet makes it a bigger target for   
   high-energy radiation from its star, so more evaporation occurs," notes Scott   
   Wolk of the Center for Astrophysics.   
       
   Blasts of stellar radiation hitting the planet at point-blank range could have   
   another effect: auroras that wrap around the planet from pole to pole, orders   
   of magnitude brighter than any Northern Lights in our own solar system. This   
   is speculative, though.   
       
   While the search for Earth-like planets proceeds, hot Jupiters are a welcome   
   albeit unexpected diversion. It makes you wonder, what will we be looking for   
   50 years from now.?   
       
   Credits:   
       
    Author: Dr. Tony Phillips |Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
   More information:   
       
   Big Weather on Hot Jupiters  -- ScienceCast video   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.94   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)