Voyager 1, the most distant spacecraft from Earth, has reached a new milestone in its quest to leave the Solar System.

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.

"When Voyager was launched, the space age itself was only 20 years old, so there was no basis to know that spacecraft could last so long," he told BBC News.

"We had no idea how far we would have to travel to get outside the Solar System. We now know that in roughly five years, we should be outside for the first time."

Dr Stone was speaking here at the American Geophysical Union (AGU) Fall Meeting, the largest gathering of Earth scientists in the world.

Particle bubble
Voyager 1 was launched on 5 September 1977, and its sister spacecraft, Voyager 2, on 20 August 1977....