Voyager 1 was the first human-made object to enter interstellar space, crossing the heliopause in 2012.
NASA launched Voyager 1 on 5 September 1977 to study Jupiter and Saturn. Its route used carefully timed gravity assists, allowing the spacecraft to gain speed without carrying enough fuel for a conventional journey between the outer planets. It returned landmark images and measurements of both worlds, including detailed observations of Jupiter’s moons and Saturn’s rings.
In August 2012, Voyager 1 passed through the heliopause, the boundary where the Sun’s solar wind gives way to the interstellar medium. NASA announced the milestone in 2013 after analyzing the spacecraft’s plasma data. The exact boundary is sometimes misunderstood: interstellar space does not mean Voyager 1 had left the entire Solar System or reached another star.
Voyager 2 followed a similar path and crossed the heliopause in 2018. Both probes continue sending extremely faint signals while operating with gradually reduced power.