text: NASA announced Monday that after 35 years of exploration, its Voyager 1 spacecraft has entered a new, unanticipated region of space near the edge of the solar system--a "magnetic highway" where charged particles take the "exit ramp" to interstellar space. 
   
   The region connects the sun's magnetic field lines to interstellar magnetic field lines, allowing "lower-energy charged particles that originate from inside our heliosphere... to zoom out, and higher-energy particles from outside to stream in," according to a written statement issued by NASA partner Johns Hopkins Applied Physics Lab. 
   
   The heliosphere is the "immense magnetic bubble containing our solar system, solar wind, and the entire solar magnetic field," according to NASA. 
   
   Scientists say they believe this is the final region Voyager 1 has to cross before reaching interstellar space. 
   
   Voyager 1's instruments showed a five-fold increase in high-energy charged particles, accompanied by a 1,000-fold drop in low-energy particles, NASA officials said. 
   
   These data would be consistent with Voyager 1's exit from the heliosphere, but Voyager 1's magnetic-field reading instrument indicates otherwise. 
   
   It shows an East-West magnetic field orientation, indicative of the sun's influence. The magnetic field in interstellar space, influenced by winds from explosions of supernovae, is thought to have a roughly North-South orientation, according to NASA astrophysicist Leonard Burlaga. 
   
   Voyager 1 may remain within the heliopause for another two to three years, but it's hard to anticipate how long it will be until the probe leaves the solar system, NASA scientists said. The heliopause is where the interstellar medium and solar wind pressures balance, the outer boundary of the solar system. 
   
   Launched in 1977 to explore the outer solar system, Voyager 1 and and its twin, Voyager 2, are the longest-serving spacecraft. Voyager 1 is currently 122 AU from Earth, and Voyager 2 is about 100 AU away. One AU, or astronomical unit, is equivalent to the distance from Earth to the sun. ||||| PASADENA, Calif. -- 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. 
   
   
   
   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 . 
   
   
   
   News Media Contact 
   
   Jia-Rui C. Cook 818-354-0850Jet Propulsion Laboratory, Pasadena, Calif.jccook@jpl.nasa.govDwayne Brown 202-358-1726NASA Headquarters, Washingtondwayne.c.brown@nasa.gov2012-381 ||||| | 7 
   
   
   
   Share Email Print 
   
   Remember when I said back in October that Voyager 1 might have finally left the solar system? Well, it turns out that the spacecraft, which has been skirting the edge of the solar system for a long time now, is finding it difficult to say goodbye. 
   
   According to scientists working on the mission, Voyager 1 has just entered a “magnetic highway“. They hope this road will lead Voyager out of the heliosphere, away from the influence of the sun’s magnetic field… eventually. 
   
   Ed Stone, Voyager project scientist, based at Caltech, explained that this highway is connected to interstellar space, but is still inside the magnetic field of the Sun. It is “a new region of the heliosphere”. NASA scientists are calling it a highway because it lets particles in and out of the solar system. 
   
   The heliosphere is a huge bubble the Sun creates around itself, through the solar wind. The interstellar medium is a particle wind outside of the solar system that pushes against the heliosphere. The boundary between the two is known as the heliopause. Before Voyager got close to the edge, scientists thought the boundary would be quite clear cut. Now they are realising that it is much messier than they anticipated. 
   
   Scientists working on Voyager are looking for three key signs to confirm when the spacecraft exits the heliosphere. We should see the particles created by high energy cosmic rays increase in number, and slow particles from inside the heliosphere should disappear. Lastly, scientists think the magnetic field will change direction, from East-West inside the heliosphere, to North-South outside it. There are three instruments on Voyager to measure these three signs. 
   
   This magnetic highway is within the heliopause. If you’re counting that as the boundary to the solar system (and I am), that means Voyager is still within the solar system. But it is surrounded by particles from outside the heliosphere. “Now Voyager is in a region still in the magnetic highway where it’s surrounded almost entirely by cosmic ray particles that have come in from outside,” says Stone. 
   
   The first sign of this new region came on July 28 when the intensity of solar particles dropped by a factor of two, But, within five days of falling, the intensity of particles came back up. On August 13 there was another dip. And, shortly after, another return to the previous level. You can see these dips on the figure below. 
   
   You will probably also notice is that there was a third dip, around August 25. This was the graph that kick started the speculation back in October about Voyager possibly leaving the solar system. But the reality was more complicated than that. 
   
   For seven years, since it passed the termination shock in December 2004, Voyager had been in a region where slow-moving particles from the sun randomly move in all directions. But August 25 was the day it crossed over into the magnetic highway. Now suddenly it is in a new region where particles from the sun are streaming out towards interstellar space, and outside particles from cosmic rays are streaming in. The intensity of solar particles dropped that day, and hasn’t picked up since. 
   
   “We are now at the highest intensity we have yet seen of the particles coming in from the outside,” says Stone. You can see that from the below figure. The top half shows the same data as above, but the bottom is the cosmic ray data. 
   
   The vital sign that wasn’t ticked off in October was changes in the magnetic field data. At the press conference today, Leonard Burlaga, Voyager magnetometer team scientist at NASA’s Goddard Space Flight Center, explained how the magnetic field intensity has increased and remained higher than before since Voyager crossed the boundary into the new magnetic highway region. 
   
   But there’s nothing to show that Voyager 1 is outside the heliosphere yet. “There’s no evidence that we have entered the interstellar magnetic field,” says Burlaga. 
   
   Voyager scientists are still not sure how long it will be before Voyager gets off this highway and finally, finally, makes it out into interstellar space. “It may take several more months, it could take several more years,” says Stone. “But we do believe this may be the very last layer between us and interstellar space.” 
   
   Voyager’s interstellar future could look a little bleak, depending on how you see it. By 2020, Voyager scientists will start powering down some instruments to save remaining power reserves. By 2025 power will be so low that all instruments will have to be turned off. After that Voyager will drift. 
   
   We may be able to ping it, now again, to check it’s still there. But it won’t be able to send us any data. Eventually, even the transmitter will stop working. Voyager 1 will be on its own. 
   
   In 40,000 years it’ll pass by one of our nearest neighbour stars. Though even that pass, at a distance of 1.6 light years, will hardly be close. After that it’ll be billions of years before Voyager gets near again to any other stars. 
   
   On the one hand, it seems sad that Voyager will wander through the stars, not able to send us information about any new worlds it encounters. On the other hand, in billions of years, Voyager might reach another star! Something humans made, out there in the universe* forever. It’s quite a nice thought. 
   
   For now though, we’re still communicating with both Voyager spacecraft. “We talk to both spacecraft everyday,” says Suzanne Dodd, Voyager project manager. “They’re both healthy and robust and continuing on with this incredible journey.” 
   
   I’m refusing to say goodbye to Voyager 1 just yet. It doesn’t seem too keen to say farewell itself, either. 
   
   *Thanks to bradmiller in the comments for pointing out that I originally mistyped ‘solar system’ here. Hopefully not a premonition…
target: – How to best learn about the edge of the solar system? Actually go there. NASA says its Voyager 1 spacecraft—which launched in 1977—has entered an area of the solar system that scientists didn't know about, the AP reports. "We do believe this may be the very last layer between us and interstellar space," says chief scientist Ed Stone. NASA is calling the region a "magnetic highway" where particles from inside the sun's magnetic sphere "zoom out, and higher-energy particles from outside to stream in." Scientists based their conclusion on Voyager's instruments, which show a 1,000-fold decrease in low-energy particles from our solar system and a five-fold jump in high-energy particles from interstellar space, reports Huffington Post. Now Voyager 1 may stay in this in-between zone for two or three years, NASA says. Then comes its future in interstellar space, reports Scientific American: powering down around 2025 and passing a neighboring star in about 40,000 years. After that, it will be billions of years before it approaches another star.