The spacecraft was originally launched in 1977 and was designed for just a five-year mission. Data from instruments aboard the spacecraft show that it crossed the outer edge of the heliosphere – a protective bubble of particles and magnetic fields produced by the Sun – on 5 November 2018.

Voyager 1 reached interstellar space in 2012 and is currently 21bn km from Earth. Even though they are out of the Sun’s bubble, the Voyagers are still technically in our solar system, Nasa said. Scientists maintain the solar system stretches to the outer edge of the so-called Oort Cloud. It will take about 30,000 years for the spacecraft to reach this distance.

“This is a very exciting time again in Voyager’s 41-year journey, so far, of exploring the planets and now the heliosphere and entering interstellar space,” Ed Stone, a Voyager project scientist based at Caltech, told a news briefing.

Scientists know that Voyager 2 has left the Sun’s influence because of four different instruments measuring solar particles and different types of rays. One of the instruments measures solar plasma and this is the first time Nasa has seen a drop in that key instrument. The same instrument was not working on Voyager 1. During their journeys, the twin Voyagers have zipped by Jupiter, Saturn, Uranus and Neptune and captured some of the clearest photographs of these planets.

“Both spacecrafts are very healthy if you consider them senior citizens,” Voyager project manager Suzanne Dodd said. She said the probes should last at least five, maybe 10 more years, but the cold – the temperature outside the vehicles is around minus 45°C – and waning power supply will eventually end their usefulness.

They will keep travelling and in 40,000 years or so either they will get close to the next stars or the stars, which are moving faster, will get close to them, Stone said.

The spacecraft was originally launched in 1977 and was designed for just a five-year mission. Data from instruments aboard the spacecraft show that it crossed the outer edge of the heliosphere – a protective bubble of particles and magnetic fields produced by the Sun – on 5 November 2018.

Voyager 1 reached interstellar space in 2012 and is currently 21bn km from Earth. Even though they are out of the Sun’s bubble, the Voyagers are still technically in our solar system, Nasa said. Scientists maintain the solar system stretches to the outer edge of the so-called Oort Cloud. It will take about 30,000 years for the spacecraft to reach this distance.

“This is a very exciting time again in Voyager’s 41-year journey, so far, of exploring the planets and now the heliosphere and entering interstellar space,” Ed Stone, a Voyager project scientist based at Caltech, told a news briefing.

Scientists know that Voyager 2 has left the Sun’s influence because of four different instruments measuring solar particles and different types of rays. One of the instruments measures solar plasma and this is the first time Nasa has seen a drop in that key instrument. The same instrument was not working on Voyager 1. During their journeys, the twin Voyagers have zipped by Jupiter, Saturn, Uranus and Neptune and captured some of the clearest photographs of these planets.

“Both spacecrafts are very healthy if you consider them senior citizens,” Voyager project manager Suzanne Dodd said. She said the probes should last at least five, maybe 10 more years, but the cold – the temperature outside the vehicles is around minus 45°C – and waning power supply will eventually end their usefulness.

They will keep travelling and in 40,000 years or so either they will get close to the next stars or the stars, which are moving faster, will get close to them, Stone said.