Voyagers 1 and 2: Where are they now?

Back in 1965 scientists working at the Jet Propulsion Laboratory (JPL) in California were studying the orbits of the planets around the Sun and thinking about sending space missions to the outer Solar System. They found that there was an upcoming arrangement of the planets that would allow spacecraft launched in 1977 to fly to Jupiter, then be flung by Jupiter’s gravity to Saturn, by Saturn’s gravity to Uranus, and by Uranus’s gravity to Neptune and out into interstellar space. They called it the “Grand Tour”. The chance only happens once every 175 years.

Over the following decade the satellites were built and readied for their missions. Voyager 2 was launched first, on 20 August 1977, followed by Voyager 1 on 5 September. Both missions went to Jupiter and Saturn, but only Voyager 2 continued to Uranus and Neptune. Both sent back thenunprecedented views of the planets as they flew at high speed, past Jupiter in mid-1979, and then Saturn more than a year later. It then took until 25 August 1989 for Voyager 2 to whizz past Neptune on its way out of the Solar System.

There is a constant wind blown off the Sun, typically at about 400km per second. That wind eventually grinds to a halt against the pressure of the very thin gas between the stars, marking the edge of the Sun’s “Heliosphere”. Now in 2022 both spacecraft have left the Heliosphere and moved into interstellar space. Voyager 1 is now over 23.5 billion km from the Earth and Sun.

Way out where they are now the Sun is 25,000 times fainter than here on Earth, but it is still by far the brightest star in the sky for the plucky little Voyager missions. They are now plunging into the dark depths of interstellar space, never to return to the Sun, probably never to pass even close to another star.

They are moving fast: 17 km per second.But the stars are very, very far away. If the Voyagers were headed for alpha Centauri the closest star system it would take them over 70,000 years.

Donald Kurtz is Extraordinary Professor at North-West University in Mahikeng.