For forty years Voyagers 1 and 2 have been traveling the solar system, visiting the giant gaseous planets Jupiter, Saturn, Uranus and Neptune as originally planned. By using the force of gravity to accelerate the craft they made the Grand Tour of the outer planets and eventually reached a speed allowing escape from the solar system which had not originally been planned. Powered by its plutonium reactor, which will continue to provide power for perhaps another 10 years, Voyager 1 is now 12 billion miles from the earth travelling at 100 000 miles per hour and at this distance radio signals take 34 hours to make the round trip. Since their launching these spacecraft have been battered by the solar wind; a stream of charged particles emanating from the sun. These particles dominate space near to the sun, travelling along the lines of magnetic force. Up until now there has been no information on what happens away from the sun in the interstellar space of our galaxy. An important question which was posed at the beginning of modern astronomy and over which there has been much speculation. Now for the very first time there are data.
It is the interstellar environment which makes up the vast majority of our galaxy whether measured by volume or mass. Instrument readings from the craft now show that the environment around Voyager 1 is no longer dominated by the sun. It has passed the heliopause, as this boundary is termed by astronomers, and is travelling in the relatively calm environment of interstellar space, orbiting the centre of our galaxy as if it were a star. So for the very first time mankind can examine directly the environment which makes up the majority of our galaxy. Such measurements have a direct bearing on basic questions such as the origins of galaxies and the universe. These observations will help to explain the discrepancies in what galaxies look like and how they move which has been construed by some as evidence for Dark Energy and Dark Matter.
In a step equivalent, for its time, to landing on the moon, man has begun the saga of interstellar travel.