A couple of weeks ago the spacecraft Voyager 1 reached the edge of the solar system, this pokey little neighbourhood we call home. In doing so it has extended it’s own record as being the furthest man-made object from planet earth. There isn’t exactly a threshold or boundary at which it can be said to be definitely outside the solar system, but in recent months scientists measuring data sent back to Earth by Voyager 1 have recorded a sudden rise in the presence of charged particles known to originate from interstellar space. Voyager 1 is now around 18 billion kilometres from the Sun, with its sister ship Voyager 2 a mere 15 billion kilometres away.
Launched in 1977, the Voyager programme has given us some of the most stunning planetary photographs of the solar system. They have visited Jupiter, Saturn, Uranus, and Neptune, as well as 48 of their moons. Each one meticulously photographed in exquisite detail. For the first time detailed images of the surface of Jupiter were sent back, along with photos of several of Jupiter’s moons, leading to several important discoveries such as the existence of planetary rings not observable from Earth as well as Volcanic activity on one of it’s moons – Io. When photographing Saturn, Voyager 1 was able to take incredible time-lapse images of the planet, showing powerful storms raging in its atmosphere.
Both Voyager 1 & 2 carry a golden disc, one which a summarised version of our planet is carried should the craft be found be alien life. The disc is a mixture of visual and audio information, carrying 116 images and a variety of natural sounds, such as those made by surf, wind, thunder and animals, including the songs of birds and whales. To this they added musical selections from different cultures and eras, spoken greetings in fifty-five languages, and printed messages from then US President Jimmy Carter and then U.N. Secretary-General Kurt Waldheim. The musical selection features artists such as Beethoven, Blind Willie Johnson and Chuck Berry. One of the leaders of the project, the great Carl Sagan, is supposedly said to have sarcastically argued against the inclusion of Johann Sebastian Bach on the grounds that it was ‘showing off’.
Sadly the plutonium power sources on the Voyager probes are designed to last until 2025. When they die, the probes will continue their silent journey through space towards other stars in the Milky Way but they will no longer transmit data back to Earth. Estimates at when Voyager may come across another star are put at around 40,000 years. Sadly even if it were to find anything of interest it would not be able to send anything back to Earth. It’s only on the edge of the Solar System after 35 years, and already it takes 16 hours and 38 minutes to transmit data back to Earth. When it does finally run out of power, the Voyager project will go down as one of the great feats of human endeavour and exploration ever undertaken.