The most distant human-made object is the spacecraft Voyager 1, which – in late February 2018 – is over 13 billion miles (21 billion km) from Earth. Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. Both spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. Now both Voyagers are heading out of our solar system, into the space between the stars. Voyager 1 officially became the first earthly craft to leave the solar system, crossing the heliopause, in 2012.
Both Voyager spacecraft were designed back in the early 1970s. They were built to take advantage of a rare grouping of planets on a single side of the sun in our solar system. This grouping, which happens only every 176 years, let the Voyagers slingshot from one planet to the next, via gravitational assists.
The Voyagers began acquiring images of Jupiter in January 1979. Voyager 1 completed its Jupiter encounter in early April of that year. Voyager 2 picked up the baton in late April and its encounter continued into August. The two spacecraft took more than 33,000 pictures of Jupiter and its five major satellites.
And then the Voyagers went further. When they were launched, no spacecraft had gone as far as Saturn, which is 10 times as far as Earth’s distance from the sun. The four-year journey to Saturn was thus a major leap, with the Voyagers arriving at Saturn nine months apart, in November 1980 and August 1981. Voyager 1 then began leaving the solar system, and Voyager 2 went on to an encounter with Uranus in January 1986 and with Neptune in August 1989.
Ed Stone – who was Project Scientist for the Voyager mission – told EarthSky some years ago:
We built the spacecraft with enough redundancy – that is, backup systems – so that they could keep going.
And keep going they did! The Voyagers have now been traveling for 41 years.
In 2017, astronomers described using the Hubble Space Telescope to look along the Voyagers’ paths. In about 40,000 years, long after both spacecraft are no longer operational, Voyager 1 will pass within 1.6 light-years of the star Gliese 445, in the constellation Camelopardalis. Meanwhile, Voyager 2 is about 10.5 billion miles (17 billion km) from Earth. Voyager 2 will pass 1.7 light-years from the star Ross 248 in about 40,000 years.
Bottom line: Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. Voyager 1 is now the most distant spacecraft from Earth.