NASA Voyager 1 Discovers New Region While Hurtling Toward Interstellar Space

NASA's Voyager 1 is more than 11 billion miles from the sun, hurtling toward interstellar space. Now, scientists have analyzed new data from the spacecraft and have found new details on the last region that Voyager 1 will cross before it leaves the heliosphere.

The heliosphere is an immense magnetic bubble around our sun. It contains our solar system, solar wind and entire solar magnetic field, extending well beyond the orbit of Pluto. Currently, Voyager 1 is hurtling toward the line between the heliosphere and interstellar space and has entered a region called the magnetic highway. This has resulted in simultaneous observations of the highest rate so far of charged particles from outside heliosphere and the disappearance of charged particles from inside heliosphere.

Researchers have actually seen two of the three signs of interstellar arrival. They've witnessed charged particles disappearing as they zoom out along the solar magnetic field; in fact, they saw these solar-originating particles decrease in intensity by more than 1,000 times. They've also seen cosmic rays from far outside zooming in. But they have yet to see the third sign: an abrupt change in the direction of the magnetic field. This would indicate the presence of the interstellar magnetic field.

Despite seeing these signs, though, researchers are still unsure exactly how far Voyager 1 has to go before it reaches interstellar space. It could be anywhere from months to years since the heliosphere extends at least eight billion miles beyond all the planets in our solar system. That's not to say that scientists aren't collecting some interesting data during the spacecraft's travels, though.

"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, in a news release. "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 domains of the sun's magnetic field."

The scientists found that in the span of about 24 hours, the magnetic field originating from the sun began piling up, rather like cars backed up on a freeway exit ramp. Yet the magnetic field barely changed direction--no more than two degrees. This means that while there are signs of entering interstellar space, Voyager 1 isn't there--yet.

"In some sense we have touched the intergalactic medium," said Merav Opher, an astronomer from Boston University, in an interview with Wired. "But we're still inside the sun's house."

Currently, the scientists are waiting for Voyager 1 to cross that critical threshold and to reveal more information about our galaxy.

Want to learn more about Voyager 1? Check out NASA's site here.