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| 1977 vintage Voyager spacecraft |
GUEST BLOG--NASA's Voyager 1 spacecraft has entered a new region at the far reaches
of our solar system that scientists feel is the final area the spacecraft has
to cross before reaching interstellar space.
Scientists refer to this
new region as a magnetic highway for charged particles because our sun's
magnetic field lines are connected to interstellar magnetic field lines. This
connection allows lower-energy charged particles that originate from inside our
heliosphere -- or the bubble of charged particles the sun blows around itself
-- to zoom out and allows higher-energy particles from outside to stream in.
Before entering this region, the charged particles bounced around in all
directions, as if trapped on local roads inside the heliosphere.
The Voyager team infers
this region is still inside our solar bubble because the direction of the
magnetic field lines has not changed. The direction of these magnetic field
lines is predicted to change when Voyager breaks through to interstellar space.
The new results were described at the American Geophysical Union meeting in San
Francisco on Monday.
"Although Voyager 1
still is inside the sun's environment, we now can taste what it's like on the
outside because the particles are zipping in and out on this magnetic
highway," said Edward Stone, Voyager project scientist based at the
California Institute of Technology, Pasadena. "We believe this is the last
leg of our journey to interstellar space. Our best guess is it's likely just a
few months to a couple years away. The new region isn't what we expected, but
we've come to expect the unexpected from Voyager."
Since December 2004, when
Voyager 1 crossed a point in space called the termination shock, the spacecraft
has been exploring the heliosphere's outer layer, called the heliosheath. In
this region, the stream of charged particles from the sun, known as the solar
wind, abruptly slowed down from supersonic speeds and became turbulent. Voyager
1's environment was consistent for about five and a half years. The spacecraft
then detected that the outward speed of the solar wind slowed to zero.
The intensity of the
magnetic field also began to increase at that time.
Voyager data from two
onboard instruments that measure charged particles showed the spacecraft first
entered this magnetic highway region on July 28, 2012. The region ebbed away
and flowed toward Voyager 1 several times. The spacecraft entered the region
again Aug. 25 and the environment has been stable since.
"If we were judging by
the charged particle data alone, I would have thought we were outside the
heliosphere," said Stamatios Krimigis, principal investigator of the
low-energy charged particle instrument, based at the Johns Hopkins Applied
Physics Laboratory, Laurel, Md. "But we need to look at what all the
instruments are telling us and only time will tell whether our interpretations
about this frontier are correct."
Spacecraft data revealed
the magnetic field became stronger each time Voyager entered the highway
region; however, the direction of the magnetic field lines did not change.
"We are in a magnetic
region unlike any we've been in before -- about 10 times more intense than
before the termination shock -- but the magnetic field data show no indication we're
in interstellar space," said Leonard Burlaga, a Voyager magnetometer team
member based at NASA's Goddard Space Flight Center in Greenbelt, Md. "The
magnetic field data turned out to be the key to pinpointing when we crossed the
termination shock. And we expect these data will tell us when we first reach
interstellar space."
Voyager 1 and 2 were
launched 16 days apart in 1977. At least one of the spacecraft has visited
Jupiter, Saturn, Uranus and Neptune. Voyager 1 is the most distant human-made
object, about 11 billion miles (18 billion kilometers) away from the sun. The
signal from Voyager 1 takes approximately 17 hours to travel to Earth. Voyager
2, the longest continuously operated spacecraft, is about 9 billion miles (15
billion kilometers) away from our sun. While Voyager 2 has seen changes similar
to those seen by Voyager 1, the changes are much more gradual. Scientists do
not think Voyager 2 has reached the magnetic highway.
Voyager 2 became the
longest-operating spacecraft on Aug. 13, 2012, surpassing Pioneer 6, which
launched on Dec. 16, 1965, and sent its last signal back to NASA's Deep Space
Network on Dec. 8, 2000. (It operated for 12,758 days.)
The Voyager spacecraft were
built and continue to be operated by NASA's Jet Propulsion Laboratory, in
Pasadena, Calif. Caltech 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.
For more information about
the Voyager spacecraft, visit: http://www.nasa.gov/voyager and
http://voyager.jpl.nasa.gov .
