NASA'S Voyager 1 probe poised to leave solar system

NASA is preparing to witness one of the most remarkable achievements of the human race.

The Voyager 1, a man-made vessel, is signalling that it is preparing to leave the grip of our solar system, and venture off into interstellar space.

Radio signals from the ship - which reach us 17 hours after transmission - indicate the craft is leaving the Heliopause, the last part of the ' bubble' around our solar system.

Ed Stone, the project's lead scientist, who oversaw the creation and launch of the craft in 1977, said: 'When we started this whole project in the 1970s one of the goals was to reach interstellar space - but none of us knew how far that would be and how long it would take. 'This is a really exciting time' The ship has spent the last 35 years steadily increasing its distance from Earth.

It is now

more

than 17,970,000,000km away, travelling at 10km a second, and detecting more energetic particles around it, implying it it at the very edge of the heliosheath, which is like a bubble around the solar system, protecting us from the cosmic winds of deep space.

Certain cosmic rays have a hard time entering the heliosphere, but as of last month, the sum of these slower particles increased by about 10 per cent.

This does not necessarily mean we have crossed over - but it means we are getting close.

Ed Stone told The Times: We're talking about going beyond the furthest reaches of our solar system.

' We haven't decided how we're going to celebrate when it happens - I expect the first thing we'll do is have a meeting.'

It will be hard to define when Voyager has left. It will not be a clean break - the molecules will thin out less, and there will be no wall or set boundary.

What will the Voyager find out there? Probably close to an absolute vacuum, save for a few long- range comets which orbit the sun.

Scientists expect to see several telltale signs when Voyager 1 finally crosses the boundary including a change in the magnetic field direction and the type of wind.

Interstellar wind is slower, colder and denser than solar wind.

still

The probe is still detecting 'spikes' in the intensity of cosmic ray electrons - scientists think it's still within the 'heliosheath', the very outer edge of our solar system.

The Voyager probe has been travelling towards the outer reaches of the solar system since 1977 - it has enough batteries to last until 2020, scientists estimate

Voyager 1 and its twin, Voyager 2, were launched in 1977 to tour the outer planets including Jupiter, Saturn, Uranus and Neptune