NASA's Voyager 1 first spacecraft to exit solar system

NASA's Voyager 1 spacecraft, launched 36 years ago - and now 19 billion kilometres from the Sun - has become the first man-made object to venture into interstellar space, the US space agency has said.

The new and unexpected data indicate Voyager 1 has been travelling for about a year through plasma, or ionised gas, present in the space between stars, NASA said at a news conference, on Thursday.