Big Weather on Hot Jupiters   
       
   May 24, 2013: Among the hundreds of new planets discovered by NASA's Kepler   
   spacecraft are a class of exotic worlds known as "hot Jupiters."  Unlike the   
   giant planets of our own solar system, which remain at a safe distance from   
   the sun, these worlds are reckless visitors to their parent stars. They speed   
   around in orbits a fraction the size of Mercury's, blasted on just one-side by   
   starlight hundreds of times more intense than the gentle heating experienced   
   by Jupiter here at home."   
       
   Meteorologists watching this video are probably wondering what kind of weather   
   a world like that might have. The short answer is "big."   
       
   http://www.youtube.com/watch?v=a2GZ9COXUcA   
       
   A new ScienceCast video explores the wild weather of hot Jupiters. Play it   
   Heather Knutson of Caltech made the first weather map of a hot Jupiter in 2007.   
       
   "It's not as simple as taking a picture and--voila!-we see the weather," says   
   Knutson. These planets are hundreds of light years from Earth and they are   
   nearly overwhelmed by the glare of their parent stars. "Even to see the planet   
   as a single pixel next to the star would be a huge accomplishment."   
       
   Instead, Knutson and colleagues use a trick dreamed up by Nick Cowan of   
   Northwestern University. The key, she explains, is that "most hot Jupiters are   
   tidally locked to their stars. This means they have a permanent dayside and a   
   permanent night side.  As we watch them orbit from our vantage point on Earth,   
   the planets exhibit phases--e.g., crescent, gibbous and full.  By measuring   
   the infrared brightness of the planet as a function of its phase, we can make   
   a rudimentary map of temperature vs. longitude."   
       
   http://science.nasa.gov/media/medialibrary/2013/05/24/HAT2_temp_1bar.gif   
       
   This exoplanet weather map shows temperatures on a hot Jupiter known as   
   "HAT-P-2b". NASA's Spitzer Space Telescope is the only infrared observatory   
   with the sensitivity to do this work.  Since Knutson kick-started the research   
   in 2007, nearly a dozen hot Jupiters have been mapped by astronomers using   
   Spitzer.   
       
   The most recent study, led by Nikole Lewis, a NASA Sagan Exoplanet Fellow   
   working at MIT, shows a gas giant named HAT-P-2b. "We can see daytime   
   temperatures as high as 2400 K," says Lewis, "while the nightside drops below   
   1200K.  Even at night," she marvels, "this planet is ten times hotter than   
   Jupiter."   
       
   These exoplanet maps may seem crude compared to what we're accustomed to on   
   Earth, but they are a fantastic accomplishment considering that the planets   
   are trillions of miles away.   
       
   The maps show huge day-night temperature differences typically exceeding 1000   
   degrees.  Researchers believe these thermal gradients drive ferocious winds   
   blowing thousands of miles per hour.   
       
   Without regular pictures, researchers can't say what this kind of windy   
   weather looks like. Nevertheless, Knutson is willing to speculate using   
   climate models of Jupiter as a guide.   
       
   "Weather on hot Jupiters," she predicts, "is really big."   
       
   Over the years, planetary scientists have developed computer models to   
   reproduce the storms and cloud belts in Jupiter's atmosphere.  If you take   
   those models and turn up the heat, and slow down the rotation to match the   
   tidally-locked spin of a hot Jupiter, weather patterns become super-sized. For   
   instance, on a hot Jupiter the Great Red Spot might grow as large as a quarter   
   the size of the planet and manifest itself in both the northern and southern   
   hemispheres.   
       
   "Just imagine what that would look like--a pair of giant eyes staring out into   
   space!" says Lewis.   
       
   Meanwhile, Jupiter's famous belts would widen so much that only two or three   
   would fit across the planet's girth.   
       
   Ordinary clouds of water and methane couldn't form in such a hot environment.   
   Instead, Knutson speculates that hot Jupiters might have clouds made of   
   silicate-that is, "rock clouds."   
       
   "Silicates are predicted to condense in such an environment," she says. "We're   
   already getting some hints that clouds might be common on these planets, but   
   we don't yet know if they're made of rock."   
       
   For now just one thing is certain: The meteorology of hot Jupiters is out of   
   this world.   
       
   Credits:   
       
   Author: Dr. Tony Phillips | Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
   Nikole Lewis of MIT is a NASA Sagan Exoplanet Fellow. The Sagan Fellowship   
   Program is administered by the NASA Exoplanet Science Institute as part of   
   NASA's Exoplanet Exploration Program at JPL. Caltech manages JPL for NASA   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.93   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)