Voyager 1 Still Not Quite Out of the Solar System


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Back in December, NASA announced that the Voyager 1 probe had entered a new region at the edge of our solar system. The region was described as a "magnetic highway," where charged particles can pass into and out of interstellar space. Since that time, researchers have been anxiously awaiting data that confirms Voyager 1 has become the first man-made object to make it out of the solar system.

This week, NASA released an update on Voyager 1's situation. At 11 billion miles from the sun, the probe is still traveling through the magnetic highway on its way to interstellar space. In the meantime, new research has shed more light on the nature of the magnetic highway, also known as the depletion region.

"This strange, last region before interstellar space is coming into focus, thanks to Voyager 1, humankind's most distant scout," said Ed Stone, Voyager project scientist at the California Institute of Technology. "If you looked at the cosmic ray and energetic particle data in isolation, you might think Voyager had reached interstellar space, but the team feels Voyager 1 has not yet gotten there because we are still within the domain of the sun's magnetic field."

NASA researchers are still not sure how long it may take for Voyager 1 to hit the edge of the solar system, saying it could even take years before the probe makes it out of the sun's magnetic field. The two Voyager probes were launched in 1977 and successfully studied the solar system's four gas giants before striking out for interstellar space.

Voyager 2 is only around 9 billion miles from the sun, and has not yet reached the magnetic highway. Researchers describe the depletion region as a region of space where charged particles stream into and out of the heliosphere along magnetic field lines. Since passing into the region, Voyager 1 can now also detect cosmic rays that originate from stars other than the sun. These two measurements indicate Voyager 1 has exited the solar system, but the direction of the magnetic field measured by the probe has not changed significantly, leading researchers to believe the probe is still within the sun's magnetic field.

"We saw a dramatic and rapid disappearance of the solar-originating particles," said Stamatios Krimigis, a principal investigator for Voyager's low-energy charged particle instrument at the Johns Hopkins University Applied Physics Laboratory. "They decreased in intensity by more than 1,000 times, as if there was a huge vacuum pump at the entrance ramp onto the magnetic highway. We have never witnessed such a decrease before, except when Voyager 1 exited the giant magnetosphere of Jupiter, some 34 years ago."

(Image courtesy NASA/JPL-Caltech)