Venerable spacecraft Voyager 1 has arrived
in the most distant part of space that can be considered part of the solar
system.
NASA has labelled this region of space “a
magnetic highway for charged particles” because it contains particles radiating
out from the sun along with interstellar particles zipping into our
neighbourhood. The particles in this region of space all travel in the same
direction, a marked change from space closer to the sun where charged particles
“bounced around in all directions, as if trapped on local roads inside the
heliosphere.”
The findings in NASA’s announcement seem to
have been compiled from several presentations at yesterday’s meeting of the
American Geophysical Union (search on ‘Voyager’ from the link above to find the
presentations).
This new region of space seems not to be
entirely consistent, as NASA has stated “Voyager data from two onboard
instruments that measure charged particles showed the spacecraft first entered
this magnetic highway region on July 28, 2012.”
But the region then “ebbed away and flowed
toward Voyager 1 several times,” with each re-entry to the region finding a
stronger magnetic field although “the direction of the magnetic field lines did
not change.”
Voyager 1 re-entered the region on August
25th, “and the environment has been stable since.”
All of which sounds like roadworks on the
magnetic highway, an event that might not take Voyager's overseers entirely by
surprise, as they have said the presence of the magnetic highway was in no way
expected. It is thought that when magnetic fields near the spacecraft change
into another pattern it will signify its departure from our solar system.
That may happen today, in several months,
or some time yesterday, as it takes 17 hours for a signal from Voyager 1 to reach
Earth.
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