NASA’s twin Voyager probes, which launched in 1977, are the longest-running missions to send data home. But as their power supplies wane, scientists are saying goodbye to one instrument on each spacec

Currently, Voyager 1 is over 15 billion miles away (25 billion kilometers), and Voyager 2 is over 13 billion miles away (21 billion kilometers). The twin explorers carry a suite of scientific instruments to gather invaluable data about the interstellar medium.

There's more bad news for NASA's Voyager 1 and 2 spacecraft. The twin space probes left the solar system in 2012 and 2018 respectively, and are currently over 15 billion and 20 billion miles away from Earth.