Voyager 1, the most remote spacecraft from Earth, has reached a new landmark in its expedition to leave the Solar System.
It is now 17.4bn km (10.8bn miles) from home; the veteran probe has detected a distinct change in the flow of particles that surround it. These particles, which emanate from the Sun, are no longer travelling outwards but are moving sideways. It means Voyager must be very close to making the jump to interstellar space – the space between the stars.
Edward Stone, the Voyager project scientist, lauded the explorer and the fascinating science it continues to return 33 years after launch.
“We have gotten to the point where the wind from the Sun, which until now has always had an outward motion, is no longer moving outward; it is only moving sideways so that it can end up going down the tail of the heliosphere, which is a comet-shaped-like object,” said Dr Stone, who is based at the California Institute of Technology in Pasadena, California.
This event is an outcome of the wind pushing up against the matter coming from other stars. The boundary between the two is the “official” edge of the Solar System – the heliopause. Once Voyager crosses over, it will be in interstellar space.
Voyager is racing on towards the heliopause at 17km/s. Dr Stone expects the cross-over to occur within the next few years.