Voyager 1 left the heliosphere in 2012, not the solar system

Voyager 1 became the first spacecraft to leave the heliosphere, the Sun’s bubble of solar wind and magnetic fields, on August 25, 2012, making it the first human-made object in interstellar space. That is not the same as leaving the solar system, and NASA did not announce the crossing until more than a year later.

Heliosphere, not solar system

The heliopause marks where the solar wind gives way to the thin gas between the stars, but the Sun’s gravity reaches much farther. Its outermost family of icy bodies, the Oort Cloud, still lies ahead. NASA estimates that, at about a million miles a day, Voyager 1 will need roughly 300 years to reach the cloud’s inner edge and perhaps 30,000 years to pass beyond it.

Why the long wait for confirmation? Voyager 1’s plasma sensor no longer worked, so scientists had no direct measure of the gas around it. A solar eruption in March 2012 supplied one. When its shock reached the probe in April 2013, the surrounding plasma began to vibrate “like a violin string”, and the pitch revealed gas more than 40 times denser than in the outer heliosphere. Fainter oscillations from late 2012 let the team work back to August 2012, when particle readings had changed abruptly. The analysis appeared in Science in September 2013.

“We can now answer the question we’ve all been asking — ‘Are we there yet?’ Yes, we are.” — Ed Stone, Voyager project scientist, 2013

Launched on September 5, 1977 to tour Jupiter and Saturn, Voyager 1 overtook Pioneer 10 as the most distant human-made object in 1998. On November 18, 2026, it is due to reach one light-day from Earth, about 16 billion miles, so a radio command will take a full 24 hours to arrive.