A space probe beyond the edge of the solar system celebrated 30 years since its launch yesterday. Voyager 2 is still sending data back to Earth from a distance of 7.8 billion miles – more than three times further than distant Pluto – powered by as little energy as a light bulb.

Its sister craft, Voyager 1, was launched a couple of weeks later, on September 5, 1977, but is even further away at a distance of 9.7 billion miles, making it the most distant man-made object in space.

The two unmanned spacecraft sent back close-up views of Jupiter, Saturn and their moons, plus the first detailed images of Uranus and Neptune in their first 12 years of flight. They laid the groundwork for later missions to the planets, and were first to spot mysteries such as the hexagon on Saturn.

For the past 19 years, they have been probing conditions at the “final frontier” where the sun’s influence dies and interstellar space begins. In December 2004, Voyager 1 began crossing this region, called the heliosheath, approximately
8.7 billion miles from the sun, is where the solar wind slows as it crashes into the thin gas that fills the space between stars. Voyager 2 is expected to reach this boundary later this year.

Each spacecraft carries five fully functioning science instruments that study the solar wind, energetic particles, magnetic fields and radio waves as they cruise through this unexplored region of deep space.

The spacecraft are too far from the sun to use solar power. Instead, they run on less than 300 watts, enough to light up a bright light bulb, and provided by radioisotope thermoelectric generators.

Alan Stern, associate administrator for NASA’s Science Mission Directorate, Washington, said: “It’s a testament to Voyager’s designers, builders and operators that both spacecraft continue to deliver important findings more than 25 years after their primary mission to Jupiter and Saturn concluded.”

Stern’s own mission, New Horizons, zipped past Jupiter earlier this year on its way to study the former planet Pluto.

Picture: A Nasa artist’s impression of a Voyager passing Saturn.

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