The Voyager 1 spacecraft, launched 35 years ago to explore Jupiter and other planets, has not yet left the confines of the solar system for interstellar space — but the spacecraft, which is more than 11 billion miles from Earth, has entered a "magnetic highway," a new region of crisscrossing charged particles.
LOS ANGELES — Voyager 1, the spacecraft famous for beaming back striking photos of Jupiter, Saturn and their moons more than 30 years ago, has made still another surprising discovery: the existence of an unpredicted zone at the very edge of the solar system.
It had been thought that the NASA probe had already been passing through the outermost section of the solar system on its way toward the heliopause — the boundary where the solar wind ends and interstellar space begins.
The existence of yet another district at our cosmic neighborhood’s edge was completely unexpected, said Stamatios Krimigis, a solar physicist at the Johns Hopkins Applied Physics Laboratory in Laurel, Md., and leader of the team that operates Voyager’s low-energy charged-particle instrument.
“Nature is imaginative,” he said Monday.
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Speaking to reporters from the annual meeting of the American Geophysical Union in San Francisco, Krimigis and former Jet Propulsion Laboratory director Edward Stone described the newfound region as a “magnetic highway” that connects the heliosphere, the bubble surrounding the solar system, to the vast expanse of space beyond.
NASA researchers said in September they thought Voyager 1 might pass out of the solar system by the end of the year.
As the craft neared the heliopause, scientists expected to detect fewer particles of solar wind and more cosmic rays pouring in from interstellar space. They also expected the magnetic field to change direction.
Since late July, Krimigis said, the intensity of the particles had decreased a thousandfold, while cosmic-ray intensities rose.
“If we had looked at particle data alone, we would have said, ‘We’re out! Goodbye, solar system!’ ” he said.
But though they could tell the strength of the magnetic field had increased, Voyager’s instruments never detected the anticipated change in the field’s direction, said Leonard Burlaga, a member of the team that operates Voyager’s magnetometer from NASA’s Goddard Space Flight Center in Greenbelt, Md.
For this reason, he said, “there’s no evidence we’ve entered interstellar space.”
Rather, the highway region, which is created by a magnetic field originating from the southern hemisphere of our sun, appears to allow particles from within the heliosphere to escape into interstellar space while permitting particles from the outside to pour in.
Gary Zank, a space physicist at the University of Alabama in Huntsville, said that he wasn’t convinced Voyager 1 was still contained within the solar system and that it would take several months to figure out whether the probe had crossed the heliopause after all.