Hubble Discovers a New Moon Around Pluto   
       
   July 20, 2011: Astronomers using the Hubble Space Telescope have discovered a   
   fourth moon orbiting the icy dwarf planet Pluto. The tiny, new satellite -   
   temporarily designated P4 -- popped up in a Hubble survey searching for rings   
   around the dwarf planet.   
       
   The new moon is the smallest discovered around Pluto. It has an estimated   
   diameter of 8 to 21 miles (13 to 34 km). By comparison, Charon, Pluto's   
   largest moon, is 648 miles (1,043 km) across, and the other moons, Nix and   
   Hydra, are in the range of 20 to 70 miles in diameter (32 to 113 km).   
       
   "I find it remarkable that Hubble's cameras enabled us to see such a tiny   
   object so clearly from a distance of more than 3 billion miles (5 billion   
   km)," said Mark Showalter of the SETI Institute in Mountain View, Calif., who   
   led this observing program with Hubble.   
   [...]   
   This composite of two Hubble images shows Pluto's four satellites in motion.   
   [more]   
       
   The finding is a result of ongoing work to support NASA's New Horizons   
   mission, scheduled to fly through the Pluto system in 2015. The mission is   
   designed to provide new insights about worlds at the edge of our solar system.   
   Hubble's mapping of Pluto's surface and discovery of its satellites have been   
   invaluable to planning for New Horizons' close encounter.   
       
   "This is a fantastic discovery," said New Horizons' principal investigator   
   Alan Stern of the Southwest Research Institute in Boulder, Colo. "Now that we   
   know there's another moon in the Pluto system, we can plan close-up   
   observations of it during our flyby."   
       
   The new moon is located between the orbits of Nix and Hydra, which Hubble   
   discovered in 2005. Charon was discovered in 1978 at the U.S. Naval   
   Observatory and first resolved using Hubble in 1990 as a separate body from   
   Pluto.   
       
   The dwarf planet's entire moon system is believed to have formed by a   
   collision between Pluto and another planet-sized body early in the history of   
   the solar system. The smashup flung material that coalesced into the family of   
   satellites observed around Pluto.   
   [...]   
   An artist's concept of Pluto's satellite system with newly discovered moon P4   
   highlighted. Credit: NASA, ESA, and A. Feild (STScI) [more]   
       
   Lunar rocks returned to Earth from the Apollo missions led to the theory that   
   our moon was the result of a similar collision between Earth and a Mars-sized   
   body 4.4 billion years ago. Scientists believe material blasted off Pluto's   
   moons by micrometeoroid impacts may form rings around the dwarf planet, but   
   the Hubble photographs have not detected any so far.   
       
   "This surprising observation is a powerful reminder of Hubble's ability as a   
   general purpose astronomical observatory to make astounding, unintended   
   discoveries," said Jon Morse, astrophysics division director at NASA   
   Headquarters in Washington.   
       
   P4 was first seen in a photo taken with Hubble's Wide Field Camera 3 on June   
   28. It was confirmed in subsequent Hubble pictures taken on July 3 and July   
   18. The moon was not seen in earlier Hubble images because the exposure times   
   were shorter. There is a chance it appeared as a very faint smudge in 2006   
   images, but was overlooked because it was obscured.   
       
   For images and more information about Hubble, visit: http://www.   
   asa.gov/hubble.   
       
       
   Production editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
       
   Credits: Hubble is a project of international cooperation between NASA and the   
   European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md.,   
   manages the telescope. The Space Telescope Science Institute (STScI) in   
   Baltimore conducts Hubble science operations. STScI is operated for NASA by   
   the Association of Universities for Research in Astronomy Inc. in Washington.     
   http://science.nasa.gov/science-news/science-at-nasa/2011/20jul_p4/   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.63   
    * Origin: NCS BBS (1:3828/7)