NASA's Voyager 2 probe has become only the second human-made object to reach interstellar space, the agency said over the weekend. Voyager 1 is 13 billion miles from Earth and crossed into the interstellar medium in 2012, but its plasma instrument is no longer functioning.
The probe has now journeyed past the "heliopause" which marks the boundary between the solar system and interstellar space. The scientists can still communicate with Voyager 2, even in interstellar space, but the data takes about 16.5 hours to travel back to Earth. Launched in 1977, the Voyagers are now NASA's longest-running mission, having far surpassed their original 5-year assignment to study the outer planets of our solar system.
Unlike Voyager 1, Voyager 2 has instruments on board that measure changes in the speed and direction of high-energy plasma particles as the wind from our Sun meets the high-energy particles streaming in from the rest of the galaxy. Both probes returned tons of important information on the outer planets, and the missions have continued onward, taking measurements as they fly farther and farther through space.
Voyager 2 Enters Interstellar Space
About 61,000 years from now, Voyager 2 will pass beyond the Oort Cloud-a large, diffuse swarm of icy objects that is thought to extend as far as 200,000 times farther from the sun than Earth, says Wesleyan University's Seth Redfield. So we really didn't know if Voyager 2 would cross three years ago or three years from now. "This is what we've all been waiting for".
"It was about a month's worth of checking to make sure the universe wasn't playing tricks on us", Mr Nagle said.
The Voyager 2 spacecraft has now gone where only one other spacecraft has gone before, and it happens to be its twin.
Voyager project scientist Ed Stone confirmed the craft left the Solar System on November 5, 2018, when the steady stream of particles emitted from the Sun - and that was being detected by the probe - suddenly dipped.
The Voyager 2, launched in 1977, is renowned as the only probe ever to study Neptune and Uranus during planetary flybys. Its twin, Voyager 1, crossed this boundary in 2012, but Voyager 2 carries a working instrument that will provide first-of-its-kind observations of the nature of this gateway into interstellar space. "Two feels like we're becoming a society that's capable of exploring interstellar space".
This was because the planned route for Voyager 2 was significantly longer, with it being set on a flyby course with numerous outer planets, revealing the first close-ups and important scientific data on planets such as Saturn, Neptune and Uranus. Now, Voyager 2 has followed it, according to NASA.
Technically, however, Voyager 2 is still in the distant realms of the solar system. In terms of the reach of heliospheric particles or particles from the Sun, both spacecraft are effectively outside of it but they still have a long way to traverse for them to escape the influence of solar gravity. "Since the spacecraft could last billions of years, these circular time capsules could one day be the only traces of human civilization", says NASA.