Excited NASA researchers today announced that the Voyager 1 spacecraft has encountered a new, unexpected region on its way out of the solar system. The scientists believe that the region is the final hurdle before Voyager enters interstellar space.
The new region of the heliosphere - the bubble of charged particles from the sun that envelops the solar system - is being referred to as a magnetic "highway" where lower-energy particles from inside the solar system can pass out and higher-energy particles from interstellar space can stream in. Before reaching this region, the Voyager 1 and Voyager 2 observed that charged particles bounced in all directions, as if trapped inside the heliosphere.
"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, a Voyager project scientist based at the California Institute of Technology. "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."
The Voyager team believes Voyager 1 is still inside the heliosphere because the direction of the magnetic fields surrounding it has not changed. The direction of magnetic field lines is expected to change as the probe enters interstellar space.
Excitement at the Voyager probes' approach of deep space has been increasing since 2004, when Voyager 1 crossed the termination shock into the heliosheath, the outermost layer of the heliosphere.
The probe crossed into the new, unexpected magnetic highway back in July of this year. At the time, researchers thought Voyager may have been approaching interstellar space, but the region ebbed and flowed toward the probe several times. Since August 25, the region has been stable.
"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 Voyager's low-energy charged particle instrument and a researcher at the Johns Hopkins Applied Physics Laboratory. "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."
Voyager 1 and 2 were launched 16 days apart in 1977. The probes are the longest-serving NASA spacecrafts and Voyager 1 is the most distant human-made object from Earth. Voyager 1 is 122 Astronomical Units (11 billion miles) from the sun, and Voyager 2 is 100 Astronomical Units (9 billion miles) from the sun. Researchers do not believe Voyager 2 has yet reached the newly discovered magnetic highway.
"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. "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."
(Image courtesy NASA/JPL-Caltech)