Voyager 1 and its twin probe Voyager 2 were launched back in 1977 with their mission objective to explore the outer planets Saturn, Jupiter, Uranus and Neptune. After the Voyager program’s primary mission was completed successfully in 1989, the Voyager Interstellar Mission (VIM) was then initiated to extend the exploration of the solar system to the outer limits of the Sun’s sphere of influence, and possibly beyond.
It’s now been 36 years since the Voyager 1 left our planet, during which time it has traversed 25 billion kilometres of space, and is currently around 18.75 billion kilometres distant making it the furthest man-made object from Earth. It is also rapidly heading towards interstellar space (the space between the stars) at a relative velocity to the Sun of 17 kilometres per second, with signals sent from Earth taking 17 hours to reach Voyager 1.
As well as being famed for their information-collecting achievements, the Voyager probes are also renowned for containing phonographic ‘golden records’ which contain images and a variety of sounds communicating the wonders of Earth to any potential extraterrestrials advanced enough to retrieve them.
However, that it unlikely to happen anytime soon as Voyager 1 will take around 40,000 years before drifting within 1.6 light years of a star with a planetary neighbour in the constellation of Camelopardalis, while Voyager 2 will pass 1.7 light years from the star Ross 248 in the constellation of Andromeda in some 296,000 years. Nevertheless, as Carl Sagan commented at the time:
“A billion years from now, when everything on Earth we’ve ever made has crumbled into dust, when the continents have changed beyond recognition and our species is unimaginably altered or extinct, the Voyager record will speak for us.”
Finally, Voyager’s power source comes from the decay of plutonium 238, which decays just four watts a year with electrical power to support science instrument operation expected to run out in 2025. When that happens, science data return and spacecraft operations will likely cease, after which Voyager will just keep on travelling onwards in a straight line forever, or until they are affected by an external force or intercepted by aliens.