NASA's Voyager 1 spacecraft is approaching a historic milestone: becoming the first human-made object to reach a distance of one light day from Earth. Currently about 15.7 billion miles (25.3 billion kilometers) from our planet, Voyager 1 will be 16.1 billion miles (25.9 billion kilometers) away by 2026, meaning it will take 24 hours for a signal to travel between Earth and the probe.
Launched in 1977 alongside its twin, Voyager 2, Voyager 1 became the first spacecraft to enter interstellar space in 2012 and remains the farthest human-made object from Earth. From the moment Voyager 1 reaches this milestone, commands sent to the spacecraft will take a full day to reach it and another day for confirmation to return.
Voyager 1 and Voyager 2
Voyager 1's journey has already yielded iconic discoveries, including flybys of Jupiter and Saturn, and the famous "pale blue dot" image of Earth, suggested by astrophysicist Carl Sagan. Its twin, Voyager 2, crossed the outer edge of the solar system in 2018 and remains the second-most distant human-made object.
Despite having about 3 million times less memory than a modern smartphone, the Voyagers continue to function, making them the longest-running missions in NASA's history. Voyager 1's nuclear power source is expected to keep it operational for at least another year.