NASA announced Monday that Voyager 1, the spacecraft launched in 1977 with the goal of exploring the outer reaches of the solar system, has entered a new region at the "far reaches" of the solar system, and that the region is likely the last before it enters interstellar space.
Scientists at NASA's Jet Propulsion Laboratory said they expect the satellite to completely exit the heliosphere — the bubble of energy created by the sun and the physical end of the solar system — sometime in the next couple years.
"This region was not anticipated, it was not predicted, we can't predict exactly when we'll [leave it]," Edward Stone, Voyager project scientist, said in a conference call Monday.
NASA says that Voyager has now reached a "magnetic highway" in which charged particles from the sun leave the solar system and particles from outside the solar system to make their way in.
"Although Voyager 1 still is inside the sun's environment, we can now taste what it's like on the outside because the particles are zipping in and out on this magnetic highway," Stone said. "We believe this is last leg of our journey to interstellar space. Our best guess is it's likely just a few months to a couple years away."
Stone says that during its 35 year mission, the Voyager team has come to expect the unexpected. When it finally leaves the solar system, the team isn't sure what it'll find.
"Whatever we think we'll find, I'm sure we'll find something different," he said.
So far, Voyager 1 has traveled about 100 times the distance of the Earth to the Sun, or about 9.3 billion miles. The team estimates that they'll be able to continue communicating with Voyager until about 2025.
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Jason Koebler is a science and technology reporter for U.S. News & World Report. You can follow him on Twitter or reach him at firstname.lastname@example.org.