Voyager 1 passes one light-day from Earth
For the first time, a human-made object is set to pass one light-day from Earth, about 25.9 billion km (173 AU). NASA calculates the moment as 10:16:07 UTC on 18 November 2026; after that, a command takes 24 hours to arrive, and the reply two full days to come back.
The story
A light-day is the distance light travels in one day, about 25.9 billion km. That is 173 times the distance between Earth and the Sun. Light takes 1.3 seconds to reach the Moon and a little over eight minutes to reach the Sun, which gives a sense of how far a whole day of light travel is. Voyager 1, launched in 1977, has been flying at about 17 km per second for almost half a century. By NASA's calculation, it crosses this distance at 10:16:07 UTC on 18 November 2026. No human-made object has ever been this far away.
There is a reason the crossing comes in November. Voyager moves steadily away from the Sun every year, but Earth circles the Sun, so the distance between Earth and Voyager grows and shrinks over each year. Voyager 1 is heading toward the constellation Ophiuchus. The gap is widest in late November and early December, when Earth is on the far side of the Sun from that direction. So the first crossing comes in November 2026, the distance dips back inside the line the following spring, and after that Voyager stays beyond it for good.
Nothing special happens to the spacecraft on the day. No engine fires, and the signal does not change. What changes is life for the people on Earth who fly it. When the team sends a command, it takes two days to learn whether it worked, and the same two days stand between noticing a problem and fixing it. In that sense, this is a point where distance changes the way a spacecraft has to be operated.
NASA has worked out the moment of crossing down to the second: 10:16:07 UTC on 18 November 2026. The moment comes from calculating Voyager's position, so nothing is checked on the spacecraft at that instant. The meaning of the event lies elsewhere. A machine built in the 1970s is still answering calls from Earth, and by the time each answer arrives, it is already a day old.
Mission goals
In 2012 Voyager 1 crossed the heliopause and became the first spacecraft to enter interstellar space. The heliopause is the edge of a huge bubble blown by the solar wind, the stream of particles flowing out from the Sun. Beyond it lies space filled with material from other stars. The only instruments measuring things like the magnetic field and electron density directly inside that region are the ones aboard Voyager 1 and Voyager 2. Telescopes can only estimate those properties from far away.
The farther Voyager goes, the more its data is worth. How far the Sun's influence reaches, and how interstellar space changes with distance from the Sun, can only be measured where Voyager happens to be. There is no successor on the way, and even a probe launched today would need decades to reach this distance.
Voyager also tests the limits of communication. Picking a very faint signal out of the noise from a light-day away is hard even for the large antennas of NASA's Deep Space Network. Whenever probes to other stars are discussed seriously, Voyager is the example where the problem of communicating across such distances has already been faced with real hardware.
Mission chronology and background
Voyager 1 was launched in September 1977. It passed Jupiter in 1979 and Saturn in 1980, taking the first close-up pictures of many of their moons. To get a good look at Saturn's large moon Titan, it took a path that bent sharply out of the flat plane in which the planets orbit. That choice meant it could not visit Uranus and Neptune, but it put the spacecraft on a fast route out of the solar system.
In 1990 it turned around and took a last set of pictures looking back at the solar system. In one of them, Earth appeared as a tiny speck in a band of sunlight, an image that became known as the Pale Blue Dot. After that the cameras were switched off, and the mission continued with instruments that measure magnetic fields, particles and plasma. When its crossing of the heliopause was confirmed in 2012, Voyager 1 became the first human-made object to reach interstellar space.
Power is the remaining challenge. Voyager makes electricity from the heat of radioactive material, and the output drops every year. The team has been switching instruments off one by one to make the power last, and in 2026 only two science instruments are still running. The signal is expected to end sometime in the 2030s. Voyager 2 is a little slower and heading in a different direction, so it will need about ten more years to reach one light-day.
Other milestones of this mission
- Voyager 2 launch — the Grand Tour
- Voyager 1 launch
- Voyager 2 at Neptune
- Voyager 1 enters interstellar space
Where to see it — sky and simulator
Voyager 1 cannot be seen in the sky. It gives off no light of its own and is far too small and distant for any telescope. The most anyone can do is look toward Ophiuchus, knowing the spacecraft is somewhere in that direction. Following its path in the orbit view gives a much better feel for the distance.
In the orbit view, choose Voyager 1 as the tracked object and zoom out, and the planets of the solar system shrink into a single dot in the middle of the screen. Voyager sits at the end of a line running straight out from that dot. With the clock set to November 2026, the gap between Voyager and Earth is plain to see, and light needs a whole day to cross it. Rewinding to the late 1970s and 1980s shows the path bending as the spacecraft passed Jupiter and Saturn.
Live numbers are published on NASA's Voyager mission page, which shows the current distance and the one-way travel time of a signal. NASA has calculated the crossing for 10:16:07 UTC on 18 November, and the time on this page follows that figure.
See this for yourself — open it in the simulator
FAQ
How far is a light-day?
About 25.9 billion km, or 173 times the Earth–Sun distance. Light reaches the Moon in 1.3 seconds and the Sun in a little over eight minutes, which gives a sense of the scale.
Is Voyager still in contact?
Yes. The Deep Space Network still receives its very faint signal with its largest antennas. A round trip takes two days, so it is more like exchanging letters than a conversation, and fewer instruments stay on as the power declines.
How long will Voyager 1 keep working?
Its power falls every year, and the signal is expected to end sometime in the 2030s. The exact timing depends on the remaining power and the team's choices. The spacecraft will keep flying in the same direction after it falls silent.
Can I see Voyager in the sky?
No. It gives off no light and is far too small and distant for any telescope. Tracking Voyager 1 in the orbit view shows its path and its distance from Earth on screen.
Related
- Voyager 1 launches — 1977
- Voyager 1 enters interstellar space
- The Pale Blue Dot
- Voyager 1 — object index
- Voyager 2 — object index
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.