Worlds within Worlds: Hubble Peels Back the Layers of a Warm Neptune   
       
   Oct. 31, 2015:  They say you can't judge a book by its cover. But what about   
   planets?   
       
   Take Neptune for example. For many years, especially since 1989 when Voyager 2   
   flew past Neptune and measured its gravity field, astronomers have known that   
   the blue giant harbors a secret world inside. Hidden deep below the azure   
   cloud tops lies a rocky core not much larger than Earth. Uranus has one, too!   
   These "worlds within worlds" could have exotic properties including scorching   
   hot oceans and diamond rain.   
       
   If only researchers could peel back the clouds for a closer look..   
       
   Astronomers using NASA's Hubble Space Telescope have discovered an immense   
   cloud of hydrogen evaporating from a Neptune-sized planet named GJ 436b. The   
   planet's atmosphere is evaporating because of extreme irradiation from its   
   parent star.   
       
   http://youtu.be/TbWX7-ZoJAk   
       
   About 30 light years away, a Neptune-sized planetis having some of its layers   
   peeled back.   
       
   Astronomers using NASA's Hubble Space Telescope have discovered an immense   
   cloud of hydrogen evaporating from a Neptune-sized planet named GJ 436b.   
       
   "This cloud is spectacular," says the study's leader, David Ehrenreich of the   
   Observatory of the University of Geneva in Switzerland. "The research team has   
   nicknamed it `The Behemoth.'"   
       
   The planet's atmosphere is evaporating because of extreme irradiation from its   
   parent star-a process that might have been even more intense in the past.     
   "The parent star, which is a faint red dwarf, was once more active," says   
   Ehrenreich. "This means that the planet's atmosphere evaporated faster during   
   its first billion years of existence. Overall, we estimate that the planet may   
   have lost up to 10 percent of its atmosphere."   
       
   GJ 436b is considered to be a "Warm Neptune" because of its size and because   
   it is much closer to its parent star than Neptune is to our own sun. Orbiting   
   at a distance of less than 3 million miles, It whips around the central red   
   dwarf in just 2.6 Earth days. For comparison, the Earth is 93 million miles   
   from the sun and orbits it every 365.24 days.   
       
   Systems like GJ 436b could explain the existence of so-called "Hot   
   Super-Earths."   
       
   "Hot Super-Earths" are larger, hotter versions of our own planet. Space   
   telescopes such as NASA's Kepler and the French led CoRoT have discovered   
   hundredsof them orbiting distant stars. The existence of The Behemoth suggests   
   that Hot Super-Earths could be the remnants of Warm Neptunes that completely   
   lost their gaseous atmospheres to evaporation.   
       
   Finding a cloud around GJ 436b required Hubble's ultraviolet vision. Earth's   
   atmosphere blocks most ultraviolet light so only a space telescope like Hubble   
   could make the crucial observations.   
       
   "You would not see The Behemoth in visible wavelengths because it is optically   
   transparent," says Ehrenreich. On the other hand, it is opaque to UV rays. "So   
   when you turn the ultraviolet eye of Hubble onto the system, it's really kind   
   of a transformation because the planet turns into a monstrous thing."   
       
   The ultraviolet technique could be a game-changer in exoplanet studies, he   
   adds. Ehrenreich expects that astronomers will find thousands of Warm Neptunes   
   and Super-Earths in the years ahead. Astronomers will want to examine them for   
   evidence of evaporation. Moreover, the ultraviolet technique might be able to   
   spot the signature of oceans evaporating on Earth-like planets, shedding new   
   light on worlds akin to our own.   
       
   Maybe you can't judge a book by its cover, but you can judge a planet by its   
   Behemoth.   
       
       
   Regards,   
       
   Roger   
      
   --- DB 3.99 + Windows 10   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)