December 5th, 2012 by James Ayre
The Voyager 1 spacecraft, launched back in 1977, is getting closer and closer to exiting the solar system and entering interstellar space. It recently entered a new, somewhat unknown region at the edge of the solar system. The researchers that work with the spacecraft are of the mind that this is the last region before breaking into interstellar space.
Researchers have described 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.”
This region is almost definitely still inside the solar bubble, as the magnetic field’s direction lines haven’t yet changed. It’s been previously predicted that the direction of these magnetic lines will change where interstellar space begins.
“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.”
The two Voyager spacecraft left the Earth in 1977, 16 days apart. They are currently the the most distant from earth human-made objects, at around 11 billion miles from the sun. Communication with Voyager 1 is very slow because of its distance from the Earth, it takes about 17 hours each way to send and receive data or instructions.
“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.”
Both of the Voyager spacecraft were designed, built and are still operated by NASA’s Jet Propulsion Laboratory. 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.
Source: NAZsA/Jet Propulsion Laboratory
Image Credits: NASA/JPL-Caltech
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