To infinity and beyond. That is the fate of NASA’s Voyager 2 probe, which left Earth in 1977.
After more than 41 years floating through space, it has now become only the second human-made object to leave our Solar System.
Now, more than 18 billion kilometres away, it no longer feels the solar wind that characterises the heliosphere, a protective bubble of particles and a magnetic field created by the Sun.
After crossing the edge of the sphere, which extends beyond the orbit of Pluto, the probe will now drift eternally through this new, unexplored domain of interstellar space.
Voyager project scientist Ed Stone confirmed the craft left the Solar System on November 5, 2018, when the steady stream of particles emitted from the Sun — and that was being detected by the probe — suddenly dipped.
According to NASA, Voyager 2 has a working instrument on board which will be able to deliver “first-of-its-kind observations of the nature of this gateway into interstellar space”.
“I think we’re all happy and relieved that the Voyager probes have both operated long enough to make it past this milestone,” Voyager Project Manager Suzanne Dodd said in a statement. “This is what we’ve all been waiting for. Now we’re looking forward to what we’ll be able to learn from having both probes outside the heliopause.”
One of the bonuses to having two probes outside the heliosphere is that scientists will receive two completely different sets of data.
Stone said: “Well this just contributes to the number of discoveries that Voyager is making and this is one we hoped that we would be able to do and fortunately both Voyagers were working when they reached interstellar space and that was quite an achievement.”
“Voyager 1 crossed this point almost six years ago so this is now quite a different time in solar activity and now they are in different places – Voyager 1 was up and Voyager 2 is down and to the left in the southern hemisphere.”
The craft leaves the heliosphere 6 years after it’s sister probe Voyager 1.
Launched to examine the outer planets, Voyager 2 encountered Jupiter, Saturn and is the only spacecraft to study the ice giants Uranus and Neptune on its journey.
The pair’s plutonium power sources will eventually stop supplying electricity, at which point their instruments and their 20W transmitters will die.
Then they will drift forever through the “space between the stars.”
Where does the solar system end?
This is a matter of debate.
Some contend that the edge of our Solar System is the heliopause – the age of an enormous bubble of solar activity, affected by solar flares and the magnetic field of the sun.
Others meanwhile mark the end of the solar system at the edge of the sun’s gravitational influence, on the outer boundaries of the Oort Cloud – a theoretical cloud of predominantly icy planetesimals.
“Inside the bubble, most of the material has come from our sun and the magnetic field has come from our sun,” Stone explained. “Outside the bubble, most of the material comes from other stars that exploded five, ten, 15 million years ago.”
At its current speed, it will take the Voyager 2 300 years to reach the inner edge of the Oort cloud, and another 30,000 to emerge on the other side.