Voyager will live out its days circling the centre of our Milky Way Galaxy
The Voyager-1 spacecraft has become
the first manmade object to leave the Solar System.
Scientists say the probe's instruments indicate it has moved beyond the
bubble of hot gas from our Sun and is now moving in the space between the
stars.
Launched in 1977, Voyager was sent
initially to study the outer planets, but then just kept on going.
Today, the veteran Nasa mission is almost 19 billion km (12 billion miles)
from home.
This distance is so vast that it takes 17 hours now for a radio signal sent
from Voyager to reach receivers here on Earth.
"Scientifically it's a major milestone, but also historically - this is one of
those journeys of exploration like circumnavigating the globe for the first time
or having a footprint on the Moon for the first time. This is the first time
we've begun to explore the space between the stars," he told BBC News.
Sensors on Voyager had been indicating for some time that its local environment
had changed.
"This is big; it's really impressive - the first human-made object to make it
out into interstellar space," said Prof Don Gurnett from the University of Iowa
and the principal investigator on the PWS.
On 25 August, 2012, Voyager-1 was some 121 Astronomical Units away. That is,
121 times the separation between the Earth and the Sun.
Breaching the boundary, known technically as the heliopause, was, said the
English Astronomer Royal, Prof Sir Martin Rees, a remarkable achievement: "It's
utterly astonishing that this fragile artefact, based on 1970s technology, can
signal its presence from this immense distance."
Although now embedded in the gas, dust and magnetic fields from other stars,
Voyager still feels a gravitational tug from the Sun, just as some comets do
that lie even further out in space. But to all intents and purposes, it has left
what most people would define as the Solar System. It is now in a completely new
domain.
"Voyager-1 will be in orbit around the centre of our galaxy with all its stars
for billions of years," said Prof Stone.
NASA News Conference: Voyager Reaches Interstellar Space
"The idea that the spacecraft would then exit the Solar System altogether was so
way out, figuratively as well as literally, that we didn't even discuss it then,
although I suppose we knew it would happen someday. Forty-three years later,
that day has arrived, and Voyager is still finding new frontiers."
