The Longest Voyage - The Voyager 1 Story

An artist's impression of Voyager 1, the farthest man-made object from Earth.

The Voyager 1 space probe holds the records of most distant man-made object, fastest man-made object moving away from the Sun, and first man-made object to enter interstellar space, but next week, on November 18th, 2026, the probe will reach a new milestone. At 2:16:07 a.m. PST, the craft will be one light-day, about 16.1 billion miles (25.9 billion km), away from Earth, meaning that even traveling at the speed of light, radio communications from the probe will take 24 hours to reach Earth and another 24 hours for the response to reach it. In order to get to this major milestone, Voyager 1 has had a long and perilous journey.

What is Voyager 1?

Voyager 1, as well as its sister probe, Voyager 2, were designed to take advantage of an alignment of the gas giant planets in the late 1970s, which could allow a spacecraft to visit Jupiter, Saturn, Uranus, and Neptune in a single Grand Tour. Such a voyage would only be possible every 175 years.

The power source for the Voyagers is a radioisotope thermoelectric generator. With how far from the Sun the probes would be traveling, they couldn’t rely on the traditional solar power option. Instead, they have nuclear batteries, powered by the decay of radioactive elements. As such elements decay to a more stable state, they release heat. This heat can be captured and converted into usable power. They were also equipped with an array of scientific instruments to capture and study data from their travels.

Voyager 1 launched on September 5, 1977, 16 days after Voyager 2 had already left Earth. Despite its twin’s head start, Voyager 1 was able to overtake Voyager 2 by December 15 of the same year, thanks to a faster path it took. While the Grand Tour of the outer Solar System was the original plan, due to budget cuts, the Voyager Program focused on just Jupiter and Saturn, but with the option remaining open to travel to Uranus and Neptune, should everything still be in working order.

The Planetary Mission

Voyager 1 approached Jupiter in January of 1979. While there, it made many discoveries, including the fact that Jupiter actually had a previously unobserved system of rings far thinner than Saturn’s. It also discovered volcanoes on Jupiter’s moon Io, the first example of volcanism beyond Earth, as well as discovering two new moons—Thebe and Metis.

A picture of Jupiter's newly discovered rings taken by Voyager 2. To take this picture, the probe had to be in Jupiter's shadow so light from the Sun didn't outshine the faint light scattering off the rings.

When it was time to leave Jupiter and continue on to Saturn, Voyager 1 received a speed boost in the form of a gravitational assist from Jupiter. By swinging around the planet in just the right way, the spacecraft borrowed some orbital momentum from the gas giant to slingshot itself towards its next destination. The probe made it to Saturn by November 1980, where it discovered five new moons and a new ring around the planet.

Once at Saturn, NASA had a choice for the future of Voyager 1. While its faster trajectory meant it could never complete the Grand Tour and travel to Uranus and Neptune, it could travel to Pluto or it could take a closer look at Saturn’s largest moon, Titan. Titan was a very interesting target, as it is the only moon in our Solar System to possess a dense atmosphere. In fact, its atmosphere is four times denser than Earth’s on the surface. From far away, astronomers had no idea what was beneath the thick, hazy atmosphere, and they were very curious to learn what secrets it might hide. However, for Voyager 1 to study Titan would require the probe to travel beneath Saturn’s south pole, which would mean that the craft was no longer flying along the ecliptic of the Solar System, putting it on a trajectory that could never reach Pluto. It was decided that Voyager 1 would study Titan, so it parted ways with Voyager 2, as its twin continued on the Grand Tour towards Uranus. While studying Titan, Voyager 1 gathered plenty of data, including some that suggested the moon could have lakes of liquid methane on its surface—a hypothesis later proved true.

The Interstellar Mission

Voyager 1’s planetary mission may have been over, but the probe was still functioning and could still study space. It was already one of the most distant spacecraft ever launched, and after its slingshot around Saturn, it was left traveling at a breakneck 11 miles per second (17 km/s). At that speed, it could circle the entire Earth in roughly 39 minutes. By 1990, NASA had declared that the Voyager Interstellar Mission had begun, with a goal to explore the edges of the Solar System and beyond.

After the conclusion of its planetary mission, NASA began to shut down various instruments of the probe in order to save power. For its final usage of its camera, Voyager 1 took a series of photos of the Solar System from beyond the planets to create the Solar System Family Portrait. Its image taken of Earth at this time is the famous Pale Blue Dot, the farthest picture of Earth ever taken.

The Pale Blue Dot, the farthest picture of Earth ever taken and one of the final images captured by Voyager 1. That pale blue dot that looks like a stray blue pixel is the Earth, as seen from 3.7 billion miles away.

On February 17, 1998, Voyager 1 overtook Pioneer 10 and became the most distant man-made object, a record it maintains to this day, and will likely keep for quite some time to come, if not indefinitely. Despite how far it had come and being well beyond even Pluto’s distance from the Sun, it was still within the bounds of what we consider to be the Solar System.

In June of 2012, Voyager 1 reported a clear increase of charged particles incoming from interstellar space. These particles are usually deflected by the solar wind within our Solar System. On August 25th, 2012, Voyager 1 had passed the heliopause, the point where the outward pressure of the Sun’s solar wind is completely balanced by the incoming pressure of the interstellar medium. By some definitions, the heliopause is the edge of our Solar System, and Voyager 1 became the first man-made object to ever leave it.

The Fate and Legacy of Voyager 1

However, if one defines the Solar System by the objects that orbit the Sun, rather than by the range of the solar wind’s influence, Voyager 1 still has a long way to go. It has yet to pass the far orbit of the dwarf planet Sedna, for example. Then there’s the Oort Cloud, a cloud of billions of icy bodies orbiting the Sun at extreme distances, speculated to stretch up to 1.6 light-years away from the Sun. At its current rate, Voyager 1 wouldn’t even reach the inner Oort Cloud for another 300 years, and it would take another 30,000 years to pass all the way through.

To make it to another star would take far longer. The closest star to the Sun is Proxima Centauri, which is about 4.2 light-years away. That’s about 1,500 times more distant than Voyager 1’s single light-day. And it’s not even pointed at Proxima Centauri. Even if it was, it would take the probe over 73,000 years to reach the star.

The probe isn’t actually aiming towards any one specific star. In approximately 40,000 years it will pass within 1.6 light-years of the star Gliese 445. The star is currently 17.1 light-years from Earth, but is moving generally towards us at about 74 miles per second (119 km/s), so it will meet Voyager 1 in the middle.

NASA has continued to extend Voyager 1’s life by selectively shutting down its instruments and applying a few clever fixes, but as the probe’s power output dwindles, it will soon hit a point where it will be unable to power any of its instruments. Today only two instruments remain functioning—the magnetometer and the plasma wave subsystem. Even if it holds out, by 2035, the probe will have traveled so far that it will be out of range of NASA’s Deep Space Network and communication will be lost for good. From that point on, Voyager 1 will continue its never-ending voyage through interstellar space on its own.

The golden record, carrying the sounds of Earth out beyond our Solar System aboard Voyager 1 and 2. Perhaps it will be how an alien civilization first learns of Earth.

Perhaps someday, thousands, tens of thousands, or even millions of years from now, an alien civilization will recover what remains of Voyager 1. Maybe they’ll even be able to recover information about us from the probe’s famous golden record. And who knows where we’ll be when that happens. Maybe we’ll be gone, with Voyager 1 as one of the sole remaining testaments to our species and its accomplishments. Or maybe we’ll have moved on from Earth and outraced the forgotten probe to a new home around another star. Even as its voyage as a scientific instrument comes to a close, its voyage as a symbol of our sense of exploration will live on as the probe continues its odyssey of cosmic proportions.