A still image and set of animations show Voyager 1 in the "magnetic… (NASA/JPL-Caltech )
Voyager 1 is this close to interstellar space -- probably. On its way out of our solar system, the spacecraft has stumbled across a surprise: a "magnetic highway" that represents a brand-new, unexpected layer between here and out there.
This new layer, scientists said Monday morning, provides hints of interstellar space.
Edward Stone, Voyager project scientist, told reporters at the American Geophysical Union meeting in San Francisco on Monday that particles were "zipping in and out on this magnetic highway."
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Both Voyagers 1 and 2 are pressing on the outer boundaries of the solar system, nearing the heliopause, where the sun's influence peters out and interstellar space begins. Voyager 1 is about 11 billion miles from the sun; Voyager 2, about 9 billion.
[For the Record, 6:20 a.m. Dec. 4: An earlier version of this post stated that Voyager 1 is about 11 billion miles from space. It is that distance from the sun.]
No spacecraft has reached heliopause, ever, so the fact that there was a surprise shouldn't really be all that surprising. There are things, Stone said, we just do not know until we get there.
In December 2004, Voyager 1 crossed termination shock, where the solar system's outer layer, the heliosheathe, began, according to NASA. The environment around the spacecraft was consistent and unsurprising for about 5 1/2 years.
Then, in 2012, the outward speed of the solar wind slowed to zero, and the intensity of the magnetic field began to increase -- evidence of this magnetic highway.
Based on particle data alone, scientists might have been fooled into believing Voyager 1 had crossed into interstellar space, said Stamatios Krimigis, principal investigator for Voyager's low-energy charged particle instrument.
"We would have said, 'We're out. Goodbye, solar system,' but nature is very imaginative, and Lucy pulled out the football again."
Stone said Monday that scientists expect Voyager to take a couple of years to cross this highway, after which it will continue on, likely to come across new surprises in the heliopause.
According to NASA, the Voyagers will keeping motoring into the 2020s. By 2020, there will no longer be enough power for all the instruments, and some will be powered down. By 2025, there won't be power for any of the instruments. The spacecraft should continue on, and in about 40,000 years, Voyager 1 will come within 9.3 trillion miles of the star AC+79 3888, in the constellation Camelopardalis. Voyager 2 will come within 25 trillion miles of Sirius in about 296,000 years.
For now, said Voyager project manager Suzanne Dodd, "we do talk to both spacecrafts every day, and they're both healthy and robust and continuing on with this incredible journey."