Voyager 1 Is About to Become One Light-Day from Earth
Launched on 5 September 1977, Voyager 1 is the most distant object ever made by people. On 18 November 2026 it crosses a milestone no spacecraft has reached before: it will be one light-day from Earth, about 25.9 billion kilometres away. A radio signal sent from Earth that day will take a full 24 hours to reach it, and its reply another 24 hours to come back.
What is a light-day?
A light-day is how far light travels in one day: 299,792 km every second, times 86,400 seconds, or about 25.9 billion km. That is roughly 173 times the distance from Earth to the Sun. For comparison, sunlight reaches Earth in 8 minutes 20 seconds and Neptune in about 4 hours. The nearest star, Proxima Centauri, is 4.2 light-years away, more than 1,500 times farther than Voyager 1 will be.
When exactly does it happen?
Working from NASA JPL's Horizons trajectory and the DE440 ephemeris, Voyager 1 passes one light-day from Earth at about 10:16 UTC on 18 November 2026. Its distance from Earth does not grow perfectly evenly: Voyager 1 moves away from the Sun at about 17 km/s, but Earth swings towards and away from it during the year, so the distance from Earth grows faster at some times of year than others. The Now & Here page shows the live figure and counts down to the moment.
How Voyager 1 got so far
Voyager 1 flew past Jupiter in March 1979 and Saturn in November 1980, using each planet's gravity to speed up and bend its path out of the plane of the planets. On 14 February 1990 it turned its camera back and photographed Earth as a tiny dot in a sunbeam, the famous Pale Blue Dot. In August 2012 it crossed the heliopause, the edge of the bubble of solar wind around the Sun, and became the first spacecraft in interstellar space. Its plasma wave instrument still records the faint hum of the gas between the stars, which you can hear on our Sounds of the Universe page.
Is Voyager 1 still working?
Yes, though it is running low on power. Its plutonium power source gives a little less electricity every year, so NASA has been switching off instruments and heaters one by one to keep the most important ones running. Its radio transmitter has about 23 watts, roughly the power of a refrigerator light bulb, and after travelling a light-day the signal is so faint that NASA needs the 70-metre dishes of the Deep Space Network to hear it.
Frequently asked questions
How far away is Voyager 1? About 25.9 billion km from Earth on 18 November 2026, one light-day. The Now & Here page shows the live distance.
How long does a signal take to reach Voyager 1? About 24 hours from November 2026, so a command and its answer take about two days.
What is the farthest human-made object? Voyager 1. Voyager 2, launched the same year, is the second farthest, about 21 billion km from Earth in 2026.
When did Voyager 1 leave the Solar System? It crossed the heliopause, the edge of the Sun's bubble of solar wind, in August 2012. It is still far inside the Oort Cloud, which marks the outer edge of the Sun's gravitational reach.
How long will Voyager 1 keep working? As long as its weakening power source can run at least one instrument and the radio, expected to be into the early 2030s at most.
Explore it yourself: Now & Here · Sounds of the Universe · Journey through the universe · When will the ISS pass over me?
Sources
- NASA, Voyager mission pages: launch dates, planetary flybys, heliopause crossing in August 2012 and power management. science.nasa.gov
- NASA JPL, Horizons System: Voyager 1 trajectory. ssd.jpl.nasa.gov
One light-day = 299,792.458 km/s × 86,400 s = 25,902,068,371 km. The moment of crossing is computed from the Horizons trajectory with the DE440 ephemeris for Earth's position.