NASA’s Voyager 2 probe is currently moving toward interstellar space at around 11 billion miles, or 17.7 billion kilometers, from Earth. This is more than 118 times the distance from our planet to the Sun.
Voyager 2 has been traveling through the outermost layer of the heliosphere – a vast bubble around the Sun and the planets dominated by solar material and magnetic fields – since 2007.
Voyager Project Scientist Ed Stone is based at California Institute of Technology (Caltech).
“None of us knew, when we launched 40 years ago, that anything would still be working, and continuing on this pioneering journey,” said Stone. “The most exciting thing they find in the next five years is likely to be something that we didn’t know was out there to be discovered.”
When the spacecraft reaches the outer boundary of the heliosphere, known as the heliopause, it will be the second man-made object to enter interstellar space, following Voyager 1.
Between early and late August, the Cosmic Ray Subsystem instrument on Voyager 2 has measured about a five percent increase in the rate of cosmic rays hitting the spacecraft. In addition, the Low-Energy Charged Particle instrument has detected a similar increase in higher-energy cosmic rays.
Scientists expect that Voyager 2 will experience an increase in the rate of cosmic rays as it approaches and crosses the boundary of the heliosphere. Voyager 1 recorded similar activity in May of 2012, which turned out to be just about three months before the spacecraft crossed the heliopause.
“We’re seeing a change in the environment around Voyager 2, there’s no doubt about that,” said Stone. “We’re going to learn a lot in the coming months, but we still don’t know when we’ll reach the heliopause. We’re not there yet – that’s one thing I can say with confidence.”
By Chrissy Sexton, Earth.com Staff Writer
Image Credit: NASA/JPL-Caltech