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NASA Probe Provides Insight on Solar System's Border with Interstellar Space

Reuters

   The journey of NASA's dauntless Voyager 2 spacecraft through our solar
   system's farthest reaches has given scientists new insight into a
   poorly understood distant frontier: the unexpectedly distinct boundary
   marking where the sun's energetic influence ends and interstellar space
   begins.

   The U.S. space agency previously announced that Voyager 2, the second
   human-made object ever to depart the solar system following its twin
   Voyager 1, had zipped into interstellar space on Nov. 5, 2018, at a
   point more than 11 billion miles (17.7 billion km) from the sun.
   Several research papers published Monday provided scientific details of
   that crossing.

   Both Voyager 1 and Voyager 2 were launched in 1977, designed for
   five-year missions. Voyager 1 left the solar system at a different
   location in 2012. Both are now traversing the Milky Way galaxy's
   interstellar medium, a chillier region filling the vast expanses
   between the galaxy's stars and planetary systems.

   The solar wind -- the unending flow of charged particles emanating from
   the outer atmosphere of the sun -- creates an immense protective bubble
   called the heliosphere that envelopes the solar system. The boundary of
   the solar system -- the place where the solar wind ends and
   interstellar space begins -- is called the heliopause.

   'Exciting time'

   Voyager 2's scientific instruments detected abrupt differences in
   plasma density and magnetic particles upon crossing the heliopause, the
   researchers said. The researchers said the heliopause appeared to be
   much thinner than expected.

   Plasma -- the fourth state of matter after solids, liquids and gases --
   exists in the solar system as a soup of the charged particles beaming
   continuously outward from the sun and clashing with interstellar plasma
   that darts inward from other cosmic events like stellar explosions.

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