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Voyager is still riding shock wave in interstellar space

By
Brooks Hays

PASADENA, Calif., Dec. 17 (UPI) -- NASA's Voyager 1 spacecraft is still on its history-making journey through interstellar space, and it appears its surroundings are getting louder and louder. The probe has been riding a sort of interstellar tsunami, a shock wave that first arrived in February, through interstellar space.

The ride is not only bumpy, but noisy, too -- as evidenced by a new video released by NASA this week.

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The same type of vibrations that first allowed scientists to confirm Voyager's historic entry into interstellar space -- the long-distance oscillations of a coronal mass ejection emitted by the sun -- continue to emanate into interstellar space alongside the craft.

When the reverberations of a coronal mass ejection hit the outer limits of the solar system, they crash up against the barrier of the heliosphere and send out a sort of shockwave through interstellar space. Voyager 1, scientists say, has been surfing one of these shockwaves for nearly a year now -- it's the longest shockwave astronomers have yet observed.

"Most people would have thought the interstellar medium would have been smooth and quiet. But these shock waves seem to be more common than we thought," Don Gurnett, professor of physics at the University of Iowa, explained in a recent press release.

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Gurnett, who's been studying Voyager's journey through interstellar space, presented this new shockwave data at the American Geophysical Union meeting, held in San Francisco this week.

When researchers first measured the pitch of oscillations caused by a mass ejection in 2013, the math suggested Voyager 1 was traveling through plasma 40 times denser than the plasma of the heliosphere -- the region of space dominated by the sun, the solar system. More than a year later, and the plasma is even denser.

Voyager 1 is currently more than 12 billion miles from the sun. As Voyager continues to travel farther and farther out of the solar system, the shockwave rings at a higher and higher frequency.

"The density of the plasma is higher the farther Voyager goes," Stone said. "Is that because the interstellar medium is denser as Voyager moves away from the heliosphere, or is it from the shock wave itself? We don't know yet."

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