December 3, 2012
Magnetic Highway Has Voyager 1 In Its Grip
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Lee Rannals for redOrbit.com - Your Universe Online
NASA announced at the American Geophysical Union meeting in San Francisco on Monday that its Voyager 1 spacecraft has reached a region of space no other spacecraft has reached before.
After 35 years, the Voyager 1 spacecraft has reached a new region of deep space known as a magnetic highway for charged particles. In this region, our sun's magnetic field lines are connected to interstellar magnetic field lines.
The connection in the highway allows lower-energy charged particles that originate from inside our heliosphere to zoom out, and allows higher-energy particles from outside to stream in.
NASA said the Voyager team believes this region is still inside our solar bubble because the direction of the magnetic field lines have not changed. Once Voyager breaks through to interstellar space, the direction of these magnetic field lines is predicted to change.
"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."
Voyager 1 first crossed a point in space known as the termination shock in December 2004, and since then it has been exploring the heliosphere's outer layer known as the heliosheath.
In this region, the stream of charged particles from the sun abruptly slowed down from supersonic speeds and became turbulent. Voyager 1's environment was consistent for about five and a half years.
Data from two onboard instruments on the spacecraft measured charged particles, showing the spacecraft first entered this magnetic highways on July 28, 2012. The region ebbed away and flowed toward Voyager 1 several times. NASA said Voyager 1 entered the region again August 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," according to Stamatios Krimigis, principal investigator of the low-energy charged particle instrument. "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."
Data from the spacecraft revealed that the magnetic field became stronger every time Voyager entered the highway region, according to NASA.
"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, Maryland. "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 was launched along with its twin spacecraft Voyager 2 in 1977, 16 days apart. Voyager 1 is the most distant man-made object, and is floating around in space about 11 billion miles from the sun. The signal from Voyager 1 takes about 17 hours to travel to Earth.
NASA said Voyager 2 is the longest continuously operated spacecraft, and it is currently at 9 billion miles away from the Sun. The changes Voyager 2 has seen so far are more gradual, so scientists believe it has not yet reached the magnetic highway.