How far is Voyager 1 right now?

The Voyager mission in brief

The twin Voyagers left Cape Canaveral in 1977, Voyager 2 on August 20 and Voyager 1 on September 5, to use a rare line-up of the outer planets that let one spacecraft swing from planet to planet using each one's gravity. Voyager 1 flew past Jupiter in March 1979 and Saturn in November 1980, where it took a close look at Titan's thick atmosphere; that flyby bent its path up and out of the plane of the planets. Voyager 2 visited Jupiter (July 1979), Saturn (August 1981), Uranus (January 1986) and Neptune (August 1989). It is still the only spacecraft to have visited Uranus and Neptune.

Each carries a Golden Record: a gold-plated copper disc with sounds and images of Earth, greetings in 55 languages and music from Bach to Chuck Berry, with instructions for playing it etched on the cover, in case anyone ever finds it.

The one light-day moment

A light-day is the distance light travels in a day: 25,902,068,371 km, or about 173 times the distance from Earth to the Sun. Voyager 1 is the fastest object leaving the solar system and has been the most distant human-made object since February 1998, when it overtook Pioneer 10. On November 18, 2026 it becomes the first to be a full light-day away. Mission controllers already live with the delay: a command sent from the Deep Space Network takes almost a day to arrive, and the reply takes almost another day to come back.

Why the date wobbles with Earth's orbit

Voyager 1 moves away from the Sun at a steady 16.9 km/s. Earth, meanwhile, circles the Sun at about 30 km/s, so for half of the year it runs toward the side of its orbit facing Voyager 1 and for the other half away from it. Seen from Earth, Voyager 1's distance therefore grows at anything from -8 km/s (a slight shrink) to 41 km/s, depending on the season. In November Earth is moving away from the probe's direction, so the distance grows fast, about 25 km/s on the day. The distance from the Sun passes one light-day a few months later, on February 3, 2027. After the crossing, the yearly dip each spring never brings it back inside the line.

Where the Voyagers are in our sky

Voyager 1 left the plane of the planets heading north and is now in the constellation Ophiuchus, at right ascension 17.24 h and declination +12.2°, not far from Rasalhague. Ophiuchus is an evening constellation in summer and early autumn: look south to south-west after dark from the Northern Hemisphere. By late November the Sun is moving through Scorpius and Ophiuchus, and on the milestone day Voyager 1 is only 40° from the Sun, low in the evening twilight. The sky view above highlights Ophiuchus for your own location.

Voyager 2 went south after Neptune and is now in Pavo, at declination -59.7°, close to Peacock, the brightest star of the Peacock constellation. From most of the US and Europe that part of the sky never rises. That is also why only one antenna on Earth can talk to it: Deep Space Station 43, the 70-metre dish at Canberra in Australia.

Neither probe can be seen. Their radio transmitters put out about 23 watts, and by the time the signal reaches Earth it is billions of times weaker than the power of a digital watch, which is why it takes dishes 34 to 70 metres across to hear them.

The Pale Blue Dot

On February 14, 1990, at Carl Sagan's suggestion, Voyager 1 turned its cameras back toward the Sun and took 60 frames of the planets, a "family portrait" of the solar system from about 6 billion km (40 au) away. In one frame Earth is a fraction of a pixel inside a band of scattered sunlight. Sagan called it the Pale Blue Dot and wrote about it as a lesson in humility. The cameras were then switched off to save power and memory for the long cruise; the Pale Blue Dot images were among the last either Voyager took.

Into interstellar space

The Sun blows a wind of charged particles that inflates a bubble, the heliosphere, around the solar system. Its edge, the heliopause, is where the solar wind meets the thin gas between the stars. Voyager 1 crossed the termination shock (where the solar wind slows down) in December 2004 at about 94 au and the heliopause on August 25, 2012, at about 121.6 au, when its instruments saw the solar wind particles drop away and the density of plasma around it jump. Voyager 2 followed on November 5, 2018, at about 119 au, and because its plasma instrument still worked, it measured the crossing directly. Both are now sampling interstellar space, but they are still well inside the Sun's gravitational reach: the Oort cloud of comets begins perhaps 2,000 au out, and they will take around 300 years to reach it.

Power running down, instruments switching off

Each Voyager runs on radioisotope thermoelectric generators, which turn the heat of decaying plutonium-238 into electricity. Output falls by about 4 watts a year as the plutonium decays and the thermocouples age. To stretch the remaining power, engineers have switched off heaters, backup systems and, one by one, science instruments: Voyager 2's plasma science instrument in October 2024, Voyager 1's cosmic ray subsystem in February 2025 and Voyager 2's low-energy charged particle instrument in March 2025. Voyager 1 also came through a scare in late 2023, when a failed memory chip garbled its data for five months until engineers moved the code elsewhere. The plan is to keep at least one instrument running on each into the 2030s. After that the probes will drift on silently, Voyager 1 passing within 1.6 light-years of the star Gliese 445 in about 40,000 years.

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