Happy thirtieth birthday to Voyager 1! NASA launched the probe on September 5, 1977 to examine Jupiter, Saturn, and their satellites. It reached Jupiter in 1979 and Saturn in late 1980. A final gravity assist manoeuvre boosted its speed for the last time as it left Saturn.

It’s been travelling 17.2 kilometres per second (almost a million miles a day) ever since and is currently the most distant human-made object. It’s about three times farther away from the sun than Pluto right now. If you want exact numbers, as of August 22, 2007, Voyager 1 was 15.5 billion kilometres (9.7 billion miles) from the sun, according to NASA. Another less common measure is the astronomical unit (AU), which equals the distance between the earth to the sun, and Voyager 1 is over 103 AU from the sun and increasing the distance by 3 AU every year.

The best part is the old girl is still functioning. Scientists are currently keeping a close eye on the probe’s instruments to determine when it encounters the sun’s heliopause, where the pressure of the solar wind equals that of the interstellar medium. When it crosses heliopause, Voyager 1 will be the first human-made object to leave the solar system and enter interstellar space. The current estimate for when this will occur is 2015 but no one’s certain. It’s uncharted territory.

Even then, Voyager 1 will continue to function until about 2020, when its plutonium powered thermoelectric generator will no longer be able to supply enough electricity to power the spacecraft’s communication system and instruments. Even though it’ll be dead without power, it’ll continue onwards at 17.2 kilometres per second, dutifully obeying Newton’s First Law of Motion.

Not bad for a spacecraft designed and built-in the 1970s to complete a four-year mission.