While the average smartphone gives up after three years, the Voyager 2 space probe – which has now reached 40 – is still working. The probe has now even officially left the solar system. This provides new insights into the thin external border of our space home.
The fall of The Wall, the Chernobyl disaster and the introduction of the world wide web: these are just some of the historical events that took place while Voyager 2 flew through the solar system at over 55,000 kilometers per hour. In 1989 the probe passed ice giant Neptune, the outer planet of the solar system. Since then he has set course for the exit.
He has now succeeded in that mission. Voyager 2 exchanged our solar system on November 5, 2018 for the so-called interstellar space, the cosmic wilderness between the stars. Scientists write that on Monday in five scientific articles in the journal Nature Astronomy. Twin brother Voyager 1 preceded him in 2012. Both probes are the only man-made objects that have sunk so far into the sparkling depth of the cosmos.
Determining when an object leaves the solar system is not easy. There is no border post at the end of the solar system and we do not have a Google Solar System on which a clear border has been drawn. In fact, little was known about what the external border looks like and where it exactly lies.
Exactly where you lay the boundary of the solar system is therefore somewhat arbitrary. Some astronomers place it at the so-called Oort cloud – an area full of roaming space stones at 300 billion kilometers from the sun, which still feel the sun’s gravity. The Voyager mission team uses a boundary a bit closer to home: the point where you can no longer feel the solar wind – a fanning stream of charged particles coming from the surface of the sun.
The journey of the 42-year-old Voyager probe therefore provides rare new insights into the suburbs of our cosmic home. The outer border, for example, turned out to be thinner than expected, while the magnetic fields were stronger just beyond that border. Astronomers are interested in those details because they can teach us more about such boundaries around stars other than the sun.
That Voyager 2 probably left the solar system in 2018, the American space agency Nasa already announced last December. The articles in Nature Astronomy now constitute the final confirmation of this and provide an initial scientific analysis of the measurement data collected by the probe.
The Voyager probes became world famous thanks to the gold plates they carry, full of music, sounds and images of the earth, meant as a kind of time capsule that tells the story of our world to any aliens they might encounter along the way.
Although it seems unlikely that the probes will suddenly encounter a civilization in the vast emptiness of the universe, they still have time. The batteries in the probes are expected to last only five years – after which the collection of measurement data is forced to stop – but then they simply continue their journey through the cosmos.
The next cosmic meeting is scheduled for 40,000 years. Then Voyager 1 flies past star Gliese 445, at 17.6 light years from Earth. But even then it is not over yet. The two Voyager probes are expected to fly through the space for billions of years.