NASA's Voyager 2 reaches interstellar space - 11 billion miles from earth

NASA's Voyager 2 reaches interstellar space - 11 billion miles from earth

As NASA's Voyager 2 spacecraft enters interstellar space, project officials have high hopes that it and its twin spacecraft will continue to operate for as long as a decade. Instead, it means Voyager 2 has left the heliosphere, the pocket of particles and magnetic fields created by our closest star. The spacecraft is now beyond the outer boundary of the heliosphere, some 18 billion kilometres from Earth. It was this instrument that observed a "steep decline" in solar wind particle speeds on November 5, this being "the most compelling evidence" of entering interstellar space, according to NASA.

This illustration shows the positions of NASA's Voyager 1 and Voyager 2 probes, outside of the heliosphere, a protective bubble created by the Sun that extends well past the orbit of Pluto.

"Working on Voyager makes me feel like an explorer because everything we're seeing is new", said John Richardson, principal investigator for the PLS instrument and a principal research scientist at the Massachusetts Institute of Technology. One of the instruments measures solar plasma and this is the first time Nasa saw a drop in that key instrument; the same instrument wasn't working on Voyager 1. Launched in 1977, it is the only spacecraft to study all four of the solar system's giant planets at close range, and is NASA's longest-running mission.

The Voyager 2 is no stranger to milestones.

Neither probe has left our solar system, however, and won't be doing so anytime soon. Scientists maintain the solar system stretches to the outer edge of the so-called Oort Cloud, a sphere of icy bodies millions of miles away which will take thousands of years to traverse.

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Voyager 2 has an instrument known as a Plasma Science Experiment (PLS) onboard. Voyager 2 also made flybys of Uranus and Neptune. "Now we're looking forward to what we'll be able to learn from having both probes outside the heliopause".

At its current speed, Voyager 2 most likely wouldn't reach the inner edge of the Oort Cloud for another 300 years.

"There is still a lot to learn about the region of interstellar space immediately beyond the heliopause", said Voyager project scientist Ed Stone, a JPL veteran who's now based at Caltech. Each probe contains a 'Golden Record', curated by Carl Sagan and Ann Druyan that contains a collection of music, sounds, and images from earth.

She said the probes should last at least five, maybe 10 more years, but the cold - the temperature outside the vehicles is about minus 45C - and waning power supply will eventually end their usefulness. NASA's DSN, managed by JPL, is an worldwide network of antennas that supports interplanetary spacecraft missions and radio and radar astronomy observations for the exploration of the solar system and the universe.

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