From Nature,
But with Voyager 1 firmly outside the heliosphere, “it’s a whole new mission”, Stone says. Until about 2025, when the craft is expected to run out of its plutonium power source, Voyager 1 can explore the magnetic field, cosmic rays and density of interstellar space. Voyager 2, now 102 astronomical units (15 billion kilometres) from the Sun, is only a few years behind in joining its sister craft in the vastness of space beyond the solar bubble.