The Voyager probes

A once-in-176-years lineup

In the late 1970s Jupiter, Saturn, Uranus and Neptune lined up in a way that happens about once every 176 years. A spacecraft could swing past one planet and use its gravity to bend its path toward the next, gaining speed each time. This trick is called a gravity assist.

NASA's Jet Propulsion Laboratory built two identical probes to make use of it. Voyager 2 launched first, on August 20, 1977, and Voyager 1 followed on September 5 on a faster path. The plan to visit all four giant planets became known as the Grand Tour.

The planetary tour

Both probes reached Jupiter in 1979. They found active volcanoes on the moon Io, the first seen anywhere beyond Earth, and a thin ring around the planet. At Saturn in 1980 and 1981 they revealed complex ring structure and studied the hazy moon Titan.

Voyager 1's close pass by Titan threw it up and out of the plane of the planets. Voyager 2 carried on alone, reaching Uranus in 1986 and Neptune in 1989. It found new moons and rings at both, and geysers on Neptune's moon Triton. No other spacecraft has visited these two planets.

In 1990 Voyager 1 turned its camera back and photographed Earth from about 3.7 billion miles away. In that image, called the Pale Blue Dot, our planet is a speck smaller than a pixel.

The Golden Record

Each Voyager carries a 12-inch gold-plated copper disc, along with a needle and picture instructions for playing it. A team led by astronomer Carl Sagan chose its contents.

The record holds greetings in 55 languages, sounds such as rain, thunder and a heartbeat, music from many cultures, and more than 100 images encoded as signals. The cover includes a map showing the Sun's position relative to nearby pulsars. The chance that anyone finds it is tiny, but it is a portrait of Earth meant to last for a very long time.

Into interstellar space

The Sun blows a constant stream of charged particles, the solar wind, which carves out a huge bubble called the heliosphere. Its edge, the heliopause, is where the solar wind meets the thin gas between the stars.

Voyager 1 crossed the heliopause in August 2012, at about 11 billion miles from the Sun, becoming the first human-made object in interstellar space. Voyager 2 followed in November 2018. Because Voyager 2 still had a working plasma instrument, it gave the first direct measurement of that boundary.

Status as of 2026

The probes run on radioisotope generators, which turn heat from decaying plutonium into electricity. Output drops about 4 watts per year, so engineers have been switching off heaters and instruments one by one to keep the spacecraft alive.

In April 2026 the team turned off Voyager 1's low-energy charged particle instrument, leaving two science instruments that measure magnetic fields and plasma waves. Voyager 2 also runs a reduced set. Both still send data, though weakly: their radio transmitters use about the power of a refrigerator light bulb.

Around November 18, 2026, Voyager 1 reaches about 16.1 billion miles from Earth, so far that its signal takes a full day to arrive. Voyager 2 is a few billion miles behind and heading in a different direction. NASA expects the probes to fall silent sometime around the end of the 2020s or early 2030s, but they will keep coasting through the galaxy for millions of years.

Following the Voyagers yourself

The probes are far too faint to see with any telescope. NASA's Voyager website shows a live counter of each probe's distance from Earth and the Sun, and the free Eyes on the Solar System tool lets you see where they are in 3D.

If you look toward the constellation Ophiuchus in the summer evening sky, you are looking roughly in Voyager 1's direction. Voyager 2 is heading toward the southern constellations Sagittarius and Pavo.