Voyager 1 will be one light-day from Earth on November 18, NASA says

NASA's Voyager 1, launched in 1977, will on Wednesday, November 18, become the first human-made object to be one light-day from Earth, the distance light covers in 24 hours. NASA puts that at 16,094,799,096 miles (25,902,068,356 kilometers) and times the crossing to 5:16:07 a.m. EST. The agency said on November 10, 2026, that it will mark the day with a worldwide light display the evening before and a briefing at its Jet Propulsion Laboratory (JPL) in Southern California the day after.

The probe itself will notice nothing, according to NASA: neither its surroundings nor anything on board changes as it passes the mark. What the distance changes is the wait. From November 18, a command sent from Earth needs a full day to arrive, and the answer needs another. “If you want to say ‘hello’ to Voyager, you send your message and then you go home and you wait two days before you finally get a response,” said Suzanne Dodd, the Voyager project manager at JPL.

How NASA will mark it

After sunset on Tuesday, November 17, NASA wants people everywhere to point a light at the sky and flash VGR, the mission's call sign, in Morse code. It has set up a web page that turns a phone or tablet into the flasher, and it hopes the signals will add up to a band of golden light moving around the planet as night falls.

On Thursday, November 19, at noon EST, JPL will host a moderated discussion on the condition of both Voyagers, the science they still return from interstellar space and the difficulty of running them at such distances, followed by questions from reporters and the audience. The panel includes Nicky Fox, associate administrator of NASA's Science Mission Directorate, Dodd and mission manager Kareem Badaruddin. NASA says the event will also preview a NASA+ documentary planned for 2027, the mission's 50th anniversary.

Far, and still slow by light's standards

Voyager 1 launched on September 5, 1977, so it will have taken a little over 49 years and two months to get this far. It is traveling at nearly 38,000 mph (61,000 km/h), which the agency calls a crawl next to the speed of light. It left the heliosphere, the bubble of particles and magnetic fields blown out by the Sun, in August 2012, and is heading toward a star called AC +79 3888, or Gliese 445, more than 17 light-years away. NASA expects it to pass within about 1.7 light-years of that star in 40,000 years.

Its twin, Voyager 2, launched two weeks earlier on a route past Uranus and Neptune, entered interstellar space in 2018 and should reach one light-day from Earth in November 2035, NASA says.

Running on less power

The milestone comes as the spacecraft's power runs down. Both Voyagers draw electricity from radioisotope thermoelectric generators, which turn the heat of decaying plutonium into power, and each loses about 4 watts a year, NASA says. On April 17, engineers switched off Voyager 1's Low-energy Charged Particles experiment, which had run almost without a break since launch. Badaruddin said then that the probe still had two working science instruments, one for plasma waves and one for magnetic fields.

In early September, the team replaced three devices that help keep Voyager 1 warm with three lower-power alternatives, all at once, in an operation it nicknamed the “Big Bang.” NASA said on October 29 that the swap will let the remaining instruments run longer than expected, and that without it another instrument would have had to be switched off as early as summer 2027.

The probe also went briefly quiet in October. NASA's Deep Space Network could not detect its signal on October 18 or 19; it reappeared on October 20, and contact has held since, the agency said. Engineers found that one group of thrusters had gone offline and backups had switched on automatically, and they were still looking for the cause as of October 29.