Voyager 1 Is About to Be One Light-Day From Earth — What That Means and How to Wave at It

Next week, a spacecraft launched when Jimmy Carter was president will cross a line no human-made object has ever crossed. On Wednesday, November 18, 2026, NASA's Voyager 1 will be exactly one light-day from Earth — so far away that a radio signal sent from Earth will take a full 24 hours to reach it

It is a distance almost impossible to picture: 25.902 billion kilometres, or 16.094 billion miles. And NASA is not marking it quietly. On the evening before, the space agency is asking people all over the world to step outside after sunset and flash a torch at the sky — a symbolic wave to a probe that has been travelling for 49 years.

What is a light-day?

A light-day is not a unit of time. It is a distance: how far light travels in one 24-hour day. Light moves at about 300,000 kilometres per second, so in a day it covers roughly 25.9 billion kilometres. When Voyager 1 crosses that mark at 5:16 a.m. Eastern time on November 18 — 10:16 a.m. UTC, 3:46 p.m. in India — it becomes the first spacecraft in history to be a full light-day from home.

The practical consequence is strange to think about. Every command NASA sends to Voyager 1 now takes a day to arrive, and every reply takes another day to come back. A conversation with the spacecraft has a minimum round trip of 48 hours. The probe is travelling at about 38,000 miles per hour (61,000 kilometres per hour), yet the gap keeps growing by the hour.

A 49-year journey into interstellar space

Voyager 1 launched on September 5, 1977, on a mission that was originally supposed to last about five years — a tour of Jupiter and Saturn. It flew past Jupiter in 1979 and Saturn in 1980, sending back the first close-up images of those worlds, and then kept going. In 1998 it became the most distant human-made object from Earth, overtaking Pioneer 10. In 2012 it crossed the heliopause, the outer boundary of the Sun's protective bubble, and entered interstellar space — the region between the stars.

Both Voyager spacecraft carry the same famous cargo: the Golden Record, a gold-plated disc containing music and sounds chosen to represent life on Earth, in case anything ever finds it. Voyager 1 is still an active spacecraft, still returning scientific data from interstellar space, and it recently survived a communications hiccup in October. Its 50th launch anniversary falls next year.

How to join the celebration

NASA's public event is called "Shine Bright for Voyager's Light-Day", and it takes place after sunset on Tuesday, November 17, wherever you are. The idea is simple: point a flashlight, a phone or a glow stick at the sky and flash the letters V-G-R — Voyager's call sign — in Morse code. V is three short flashes and one long one; G is two long flashes and one short one; R is short, long, short. NASA has built an automated flasher web page that does the Morse code for you on a phone or tablet, and it is inviting people to share photos and videos of their lights by tagging @NASA.

The agency is honest about the symbolism: Voyager 1 cannot see your torch, and your light is not a signal it can receive. The point is the gesture — a wave of golden light circling the planet after sunset, marking the moment humanity's farthest traveller hits a distance measured in days, not miles.

NASA's Jet Propulsion Laboratory will follow up with a moderated discussion on Thursday, November 19, at 12:00 p.m. Eastern time, featuring mission experts and NASA leadership, streamed on NASA Live. The discussion will cover the operational status of both Voyager spacecraft, the science they are still doing in interstellar space, and the technical challenge of keeping machines alive across such distances. NASA will also preview an upcoming Voyager documentary due on its NASA+ streaming service in 2027, to mark the mission's 50th anniversary.

Why this milestone matters

One light-day is an arbitrary line in one sense — there is no physical boundary at that distance, and Voyager 1 crossed the heliopause, a real boundary, back in 2012. But it is a useful way to grasp a scale that defeats normal numbers. The Moon is about 1.3 light-seconds away. The Sun is about 8 light-minutes away. Voyager 1 is about to be a full light-day away — more than 170 times farther than the Sun.

It is also a reminder of what the mission has become. Voyager 1 was built to last five years and study two planets. Nearly half a century later it is still working, still sending data home from a place no spacecraft has been, and still — for one evening next week — able to make people all over Earth step outside and wave at the sky. For a machine that old, in a place that far away, that is a remarkable second act.

For more on NASA's current deep-space work, see how NASA's twin ESCAPADE probes slingshotted around Earth to reach Mars, and how bad Earth's space junk problem has become. According to NASA and EarthSky, the crossing is expected at 5:16 a.m. Eastern time on November 18, 2026.