NASA Spacecraft Maps the Solar System's Tail   
       
   July 10, 2013:  Like a comet, the solar system has a tail. NASA's Interstellar   
   Boundary Explorer (IBEX) has for the first time mapped out the structure of   
   this tail, which is shaped like a four-leaf clover.   
       
   Scientists describe the tail, called the heliotail, based on the first three   
   years of IBEX imagery in a paper published in the July 10 edition of the   
   Astrophysical Journal.   
       
   http://www.youtube.com/watch?v=BhAzMdoOe5E   
       
   A new video from NASA explores the solar system's comet-like tail. Play it   
   While telescopes have spotted such tails around other stars, it has been   
   difficult to see whether our star produced one. The particles found in the   
   tail -- and throughout the entire heliosphere, the region of space influenced   
   by our sun -- do not shine, so they cannot be seen with conventional   
   instruments.   
       
   "By examining the neutral atoms, IBEX has made the first observations of the   
   heliotail," said David McComas, IBEX principal investigator at Southwest   
   Research Institute in San Antonio, Texas, and the paper's lead author. "Many   
   models have suggested the heliotail might look like this or like that, but we   
   have had no observations. We always drew pictures where the tail of the solar   
   system just trailed off the page, since we couldn't even speculate about what   
   it really looked like."   
       
   http://science.nasa.gov/media/medialibrary/2013/07/10/tails_med.jpg   
       
   Other stars show tails that trail behind them like a comet's tail. Scientists   
   used NASA's Interstellar Boundary Explorer to confirm that our solar system   
   has one too. From top left and going counter clockwise, the stars shown are:   
   LLOrionis; BZ Cam; and Mira. Image Credit: NASA/HST/R.Casalegno/GALEX   
       
   IBEX measures the neutral particles created by collisions at the solar   
   system's boundaries. This technique, called energetic neutral atom imaging,   
   relies on the fact that the paths of neutral particles are not affected by the   
   solar magnetic field. Instead, the particles travel in a straight line from   
   collision to IBEX. Consequently, observing where the neutral particles came   
   from describes what is going on in these distant regions.   
       
   "Since first light in 2008, the IBEX mission team has amazed us with its   
   discoveries at the interstellar boundary, including a previously unknown   
   ribbon of energetic neutral particles stretching across it," said Arik Posner,   
   NASA's IBEX program scientist in Washington. "The new IBEX image of the   
   heliotail fills in a previously blank area on the map. We are first-hand   
   witnesses of rapid progress in heliophysics science."   
       
   By combining observations from the first three years of IBEX imagery, the team   
   showed a tail with a combination of fast and slow moving particles. There are   
   two lobes of slower particles on the sides and faster particles above and   
   below. This four-leaf clover shape can be attributed to the fact that the sun   
   has been sending out fast solar wind near its poles and slower wind near its   
   equator for the last few years. This is a common pattern in the most recent   
   phase of the sun's 11-year activity cycle.   
       
   The clover shape does not align perfectly with the solar system, however. The   
   entire shape is rotated slightly, indicating that as it moves further away   
   from the sun and its magnetic influence, the charged particles begin to be   
   nudged into a new orientation, aligning with the magnetic fields from the   
   local galaxy.   
       
   Scientists do not know how long the tail is, but think that it eventually   
   fades away and becomes indistinguishable from the rest of interstellar space.   
   Scientists are testing their current computer simulations of the solar system   
   against the new observations to improve our understanding of the comet-like   
   tail streaming out behind us.   
       
   For more information about the IBEX mission, visit: http://www.nasa.gov/ibex   
       
   Credits:   
       
   Production editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More information:   
       
   IBEX is a NASA Heliophysics Small Explorer mission. The Southwest Research   
   Institute leads IBEX with a team of national and international partners.   
   NASA's Goddard Space Flight Center in Greenbelt, Md., manages the Explorers   
   Program for NASA's Science Mission Directorate in Washington.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.94   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)