Voyager 1 Approaches Interstellar Space   
       
   June 27, 2013:  Three new papers published in today's issue of Science suggest   
   that Voyager 1, now more than 18 billion kilometers from the sun, is closer to   
   becoming the first human-made object to reach interstellar space.   
       
   http://voyager.jpl.nasa.gov/   
       
   Data published in today's issue of Science suggest that Voyager 1 is nearing   
   the edge of the heliosphere. More"This strange, last region before   
   interstellar space is coming into focus, thanks to Voyager 1, humankind's most   
   distant scout," said Ed Stone, Voyager project scientist at the California   
   Institute of Technology in Pasadena.   
       
   Voyager 1 is the near the edge of the heliosphere, a vast bubble made of the   
   sun's own magnetic field.  When Voyager punches through the bubble, it will   
   exit the solar system and enter interstellar space--the realm of the stars.   
       
   The papers describe how Voyager 1's recent entry into a region called "the   
   magnetic highway" revealed two of three telltale signs of a breakthrough:   
   charged particles disappearing as they zoom out along the solar magnetic   
   field, and cosmic rays from far outside zooming in. Scientists have not yet   
   seen the third sign, an abrupt change in the direction of the magnetic field,   
   which would indicate the presence of the interstellar magnetic field.   
       
   "If you looked at the cosmic ray and energetic particle data in isolation, you   
   might think Voyager had reached interstellar space," says Stone, "but the team   
   feels Voyager 1 has not yet gotten there because we are still within the   
   domain of the sun's magnetic field."   
       
   Voyager 1 and its twin spacecraft, Voyager 2, were launched in 1977. They   
   toured Jupiter, Saturn, Uranus and Neptune before embarking on their   
   interstellar mission in 1990. They now aim to leave the heliosphere. Measuring   
   the size of the heliosphere is part of the Voyagers' mission.   
       
   Voyager 2 is about 9 billion miles (15 billion kilometers) from the sun and   
   still inside the heliosphere. Voyager 1 was about 11 billion miles (18 billion   
   kilometers) from the sun Aug. 25 when it reached the magnetic highway, which   
   appears to connect the spacecraft to interstellar space. This region allows   
   charged particles to travel into and out of the heliosphere along a smooth   
   magnetic field line, instead of bouncing around in all directions as if   
   trapped on local roads. Voyager 1 can therefore sample interstellar space   
   before it actually enters the new realm.   
       
   Scientists do not know exactly how far Voyager 1 has to go to reach   
   interstellar space. They estimate it could take several more months, or even   
   years, to get there. The arrival could come at any time, so stay tuned.   
       
   For more information about the Voyager spacecraft mission, visit:   
   http://www.nasa.gov/voyager and http://voyager.jpl.nasa.gov .   
       
   Credits:   
       
   Production editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More information:   
       
   The Science papers focus on observations made from May to September 2012 by   
   Voyager 1's cosmic ray, low-energy charged particle and magnetometer   
   instruments, with some additional charged particle data obtained through April   
   of this year.   
       
   A gauge on the Voyager home page tracks levels of two of the three key signs   
   scientists believe will appear when the spacecraft leave our solar   
   neighborhood and enter interstellar space. Check it outUpon entering the   
   magnetic highway, "we saw a dramatic and rapid disappearance of the   
   solar-originating particles. They decreased in intensity by more than 1,000   
   times, as if there was a huge vacuum pump at the entrance ramp onto the   
   magnetic highway," said Stamatios Krimigis, the low-energy charged particle   
   instrument's principal investigator at the Johns Hopkins University Applied   
   Physics Laboratory in Laurel, Md. "We have never witnessed such a decrease   
   before, except when Voyager 1 exited the giant magnetosphere of Jupiter, some   
   34 years ago."   
       
   Other charged particle behavior observed by Voyager 1 also indicates the   
   spacecraft still is in a region of transition to the interstellar medium.   
   While crossing into the new region, the charged particles originating from the   
   heliosphere that decreased most quickly were those shooting straightest along   
   solar magnetic field lines. Particles moving perpendicular to the magnetic   
   field did not decrease as quickly. However, cosmic rays moving along the field   
   lines in the magnetic highway region were somewhat more populous than those   
   moving perpendicular to the field. In interstellar space, the direction of the   
   moving charged particles is not expected to matter.   
       
   In the span of about 24 hours, the magnetic field originating from the sun   
   also began piling up, like cars backed up on a freeway exit ramp. But   
   scientists were able to quantify that the magnetic field barely changed   
   direction -- by no more than 2 degrees.   
       
   "A day made such a difference in this region with the magnetic field suddenly   
   doubling and becoming extraordinarily smooth," said Leonard Burlaga, the lead   
   author of one of the papers, and based at NASA's Goddard Space Flight Center   
   in Greenbelt, Md. "But since there was no significant change in the magnetic   
   field direction, we're still observing the field lines originating at the sun."   
       
   NASA's Jet Propulsion Laboratory, in Pasadena, Calif., built and operates the   
   Voyager spacecraft. California Institute of Technology in Pasadena manages JPL   
   for NASA. The Voyager missions are a part of NASA's Heliophysics System   
   Observatory, sponsored by the Heliophysics Division of the Science Mission   
   Directorate at NASA Headquarters in Washington.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.94   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)