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Has Voyager 1 left the solar system yet? A debate rages

ScienceNASA Voyager ProgramNASAAstronomy and Astrophysics

Voyager 1, where are you?

At a distance of more than 11 billion miles from Earth, there is little question that Voyager has traveled farther in space than any other man-made object. However, the issue of whether or not the spacecraft has left the solar system continues to inspire heated debate among scientists.

NASA insists the probe still remains within the heliosphere, that region of space that falls within the influence of our sun's magnetic field. In fact, NASA says the probe is now traveling to the very edge of the heliosphere and has encountered a mysterious boundary area called the depletion region.

But on Thursday, a new study published in The Atrophysical Journal Letters argues that Voyager 1 actually exited the heliosphere more than a year ago.

"It's a somewhat controversial view, but we think Voyager has finally left the solar system, and is truly beginning its travels through the Milky Way," said lead study author Mark Swisdak, an astrophysics researcher at the University of Maryland.

According to NASA, scientists will know conclusively that Voyager has entered interstellar space once its surrounding magnetic field changes.

For more than 35 years, the spacecraft has traveled through the bubble of magnetism that emanates from the sun, according to NASA scientists. Beyond the heliosphere however, magnetic fields emanate from the long arms of our galaxy and run in a different direction. NASA scientists have been waiting years for Voyager to register this change.

In this most recent paper however, Swisdak and colleagues say NASA has it wrong and failed to account for the theoretical phenomenon known as magnetic reconnection.

Reconnection is described as the process in which magnetic field lines can come together, break apart and then snap into new positions. It is believed to be responsible for explosive solar flares and coronal ejections.

Swisdak and his colleagues say that after running computer simulations, they believe the magnetic field of the sun and interstellar space have joined together in areas they call "magnetic islands," and that this is why Voyager has failed to detect the shift in magnetic fields. The two fields are running in the same direction.

Authors of the study say they believe Voyager crossed the envelope of the heliosphere, or heliopause, on July 27, 2012. They arrived at that date because that's when Voyager recorded a permanent drop in heliosphere-produced particles and an increase in galactic cosmic rays from outside the solar system.

On Thursday, NASA issued a written response to the study, saying it would essentially consider the author's arguments while interpreting data collected by Voyager. 

"The fine-scale magnetic connection model will become part of the discussion among scientists as they try to reconcile what may be happening on a fine scale with what happens on a larger scale," said Voyager project scientist Ed Stone of the California Institute of Technology.

"The Voyager 1 spacecraft is exploring a region no spacecraft has ever been to before. We will continue to look for any further developments over the coming months and years as Voyager explores an uncharted frontier."

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