Where will Voyager 1 end up? Not in another galaxy

Voyager 1 is never coming back. Launched in 1977, it crossed into interstellar space in August 2012 and is now the farthest spacecraft from Earth. So where does it end up? Not in another galaxy. It will stay in the Milky Way for good.

01Fast enough to leave the Sun, not the galaxy

NASA says the Voyagers are moving through space at roughly 38,000 miles per hour, about 17 km/s. A 2019 study by Coryn Bailer-Jones of the Max Planck Institute for Astronomy and Davide Farnocchia of NASA's Jet Propulsion Laboratory puts Voyager 1's final speed away from the Sun at 16.6 km/s. That is more than enough to escape the Sun's gravity.

Escaping the whole galaxy is another matter. Studies using Gaia data put the Milky Way's escape speed at the Sun's distance from the centre at about 580 km/s (Monari and colleagues, 2018) or 528 km/s (Deason and colleagues, 2019). Voyager 1 would need to go about 30 times faster than it does.

Voyager 1 also travels with the Sun, which NASA says moves around the Milky Way at about 720,000 km/h, or 200 km/s. Even with that speed added, it is still well short of what it would need to leave.

02Passing other stars

The first star Voyager 1 comes near is not very near. Bailer-Jones and Farnocchia worked out that in about 16,700 years it will pass about 3.5 light-years from Proxima Centauri, the nearest star to the Sun. All four spacecraft heading out of the Solar System, the two Voyagers and the two Pioneers, will pass at about that distance.

The star NASA usually names is Gliese 445, a small red dwarf in the constellation Camelopardalis, about 17 light-years from us today. NASA says Voyager 1 will pass within 1.6 light-years of it in about 40,000 years. Bailer-Jones and Farnocchia, using the newer Gaia data, get about 1.9 light-years in about 44,000 years.

Either way, that is more than 100,000 times the distance from Earth to the Sun. Gliese 445 is not even in the direction Voyager 1 is heading today: the star is moving much faster than the spacecraft, about 116 km/s relative to it at the encounter in their calculation, so the star will come to Voyager rather than the other way round.

03Around and around the Milky Way

So Voyager 1 will do what the Sun does: go around the centre of the galaxy. NASA says one lap takes the Sun about 230 million years.

The video says no planet will catch it, and the odds of hitting anything are tiny. Bailer-Jones and Farnocchia estimate that a spacecraft like this would take around 10²⁰ years, roughly seven billion times the present age of the universe, to collide with a star. Over billions of years it will pass much closer to some stars than it does to Gliese 445, they note, but those stars can't be picked out yet.

Nick Oberg, then at the Kapteyn Astronomical Institute in the Netherlands, has modelled the long trip. He found that Voyager 1 will bob up and down through the disc of the galaxy more than Voyager 2, he told the American Astronomical Society in 2021, as reported by Space.com.

04The record it carries

Voyager 1 carries a Golden Record, a 30 cm gold-plated copper disc. According to NASA, it holds greetings in 55 languages, 35 sounds from life on Earth, 90 minutes of music and 115 images. The cover shows the Sun's position relative to 14 pulsars, a map to where the spacecraft came from.

How long will it last? NASA's figure, from Carl Sagan's team, is more than a billion years. Oberg's work goes further. He estimated that after 5 billion years, the outward-facing side of Voyager 1's record is about 99% likely to have been damaged beyond reading by interstellar dust. The side facing the spacecraft will probably survive until the Milky Way merges with the Andromeda galaxy, about 5 billion years from now.