Voyager 2 went off its mission four decades ago to study the solar system’s four giant planets – Jupiter, Saturn, Uranus and Neptune.
And now NASA thinks the probe has reached the end of the heliosphere, which is the bubble section of space that acts as a shield protecting planets from interstellar radiation.
If the craft has made it that distance, it will become the second man-made object to go into interstellar space.
The first was its twin Voyager 1, which arrived in May 2012.
The team monitoring Voyager 2 believe it has travelled to the edge of the solar system after it recorded a 5% jump in cosmic rays, which are more common outside the heliosphere.
Ed Stone, the Voyager project scientist, said: “We’re seeing a change in the environment around Voyager 2, there’s no doubt about that.
“We’re going to learn a lot in the coming months, but we still don’t know when we’ll reach the heliopause.
“We’re not there yet – that’s one thing I can say with confidence.”