Voyager 1 departing our solar system — lest it smash into an asteroid or run afoul of a black hole, say — is seen as an eventuality, though we've waited a while. Now, NASA's Jet Propulsion Laboratory, based on data sent by the craft, is saying the explorer could become the first manmade interstellar object very soon.
NASA launched two identical Voyager probes in 1977: Voyager 2 went up first on Aug. 20, and Voyager 1 followed on Sept. 5. Both craft, now nine and 11 billion miles from Earth, respectively, have entered our solar system's heliosheath, which is "the outermost layer of the heliosphere where the solar wind is slowed by the pressure of interstellar gas," as stated by JPL. Since Voyager 1 is farther out, it'll be the first to claim the title, despite having launched over two weeks later.
JPL whipped up a visualization showing the pair's locations, which looks like this:
The heliosphere is the region of space effected by our sun, and illustrates the reach of the charged particles it gives off. (In the image above, interstellar "winds" blow from the left, which is why the bubble you see skews so much to the right.) Once the Voyager spacecraft penetrate the heliosheath, they'll be outside of our solar system's boundaries and will be traveling through the interstellar medium that fills space between stars. Data sent back by Voyager 1 — which which takes 16 hours and 38 minutes to travel between the craft's high-gain antenna and NASA's Deep Space Network — shows "a gradual increase of about 25 percent in the amount of galactic cosmic rays Voyager was encountering" since 2009, according to Ed Stone.
Ed Stone works as a Voyager scientist at the California Institute of Technology in Pasadena. This increase in cosmic rays has accelerated as of late, and as of May 7, "cosmic ray hits have increased five percent in a week and nine percent in a month," according to Stone. It's this build up that indicates to the Voyager team that the spacecraft is just about ready to pass from our solar system into what's beyond.
"When the Voyagers launched in 1977, the space age was all of 20 years old," Stone said in a statement. "Many of us on the team dreamed of reaching interstellar space, but we really had no way of knowing how long a journey it would be — or if these two vehicles that we invested so much time and energy in would operate long enough to reach it."
34 years later, it's looking like Voyager 1 will realize the team's goals, and at a time when a new era of space exploration seems just around the corner.
Voyager spacecraft visualization credit: NASA/JPL-Caltech.