The Voyager spacecraft are the frontier scouts of our species and, given their head start, they may be for ever. One day in the distant future, when the Sun expands and engulfs the Earth, they may be the only evidence that we ever existed. But last November, Voyager 1, the most distant human-made object from our planet, stopped speaking to us.
Voyager 2 was launched first, in the summer of 1977, atop a Titan-Centaur rocket from Cape Canaveral, Florida. Voyager 1 followed a couple of weeks later. It was the faster craft, and quickly overtook its sibling. The spacecraft is now 15.2 billion miles away from Earth and adding to that distance at more than 10 miles per second. So fast you wouldn’t see it if it flew overhead.
The Voyager twins were embarking on a grand tour of the giant outer planets, Jupiter, Saturn, Uranus and Neptune, photographing them and collecting scientific data. In 1977, those planets were aligned as they are only every 176 years, allowing the two spacecraft to slingshot among them, using “gravity assists” to steal a bit of the planets’ momentum and accelerate through the solar system. The solar system being a large place, the tour spanned the 1980s.