(youtube) A probe that was launched in space in 1977 has finally left the Solar System. Voyager 1 has become the first man-made spacecraft to venture into interstellar space, according to Nasa scientists. They say new data shows the probe has already been travelling through a transitional region outside a solar bubble for around a year.

The scientists managed to work that out after an eruption from the Sun reached Voyager 1 and caused the plasma around it to react in a way that could be sensed.

Plasma outside the so-called heliosphere, which is caused by the Sun's effects, is more dense and so the vibrations produce deeper sounds.

That led Nasa to the conclusion that the probe had entered interstellar space.

Voyager 1 and its twin, Voyager 2 which is five years behind, are due to have their instruments switched off after 2020 when their power runs out.

Scientists hope Voyager 1 at least can reach a point in space that is undisturbed by the Sun.