If there is anything that offers a satisfying, memorable testament to human endeavour, it’s the epic journeys of the Voyager space probes. Launched in the late 1970s, Voyager 1 and Voyager 2 (ironically, Voyager 2 launched first) have returned some incredible information about the solar system, and now they have given us a glimpse as to what the environment is like where the sun’s influence wanes.

Voyager 1 is now some 162.7 AU (astronomic units) from earth, and still going. Voyager 2 is a bit further behind, but has also reached the stage where she is at the edge of the sun’s influence. Well, I say that, but here’s where things get interesting.

The interstellar medium is where charged particles from other stars are prevalent over the particles and emissions from the sun. Voyager 1 entered this region in 2012, and Voyager 2 in 2018. Here, the sun’s solar wind is pushed back by the forces of the galaxy, as it were. However, the sun’s influence remains in other ways. Both Voyager probes are thought to be 300 years from reaching the hypothetical Oort cloud, which is believed to hold debris from the formation of the solar system. This encompassing cloud represents the very edge of the sun’s gravitational influence, and can be easily perturbed. It might take 30,000 years for the probes to cross the Oort cloud, and from there, free themselves from the sun’s gravity.

Yet, unless they themselves are disturbed, the probes will make it. It’s believed they will stop working in the 2030s, but to have lasted as long as they have, and to have returned as much information as they have, is a brilliant tribute to what happens when humanity works not out of greed or malice, but for knowledge.