Voyager makes history by travelling into space beyond the sun
Scientists are able to confirm, thanks to 'a lucky gift from the sun', that Nasa spacecraft has left the solar system and reached interstellar space
Scientists have debated for more than a year whether Nasa's 36-year-old Voyager 1 spacecraft has left the solar system and become the first human-made object to reach interstellar space.
By a fluke measurement, they now know definitively that it has.
"We made it," said lead Voyager scientist Professor Edward Stone, from the California Institute of Technology.
The key piece of evidence came by chance when a pair of solar flares blasted charged particles in Voyager's direction in 2011 and last year. It took a year for the particles to reach the spacecraft, providing data that could be used to determine how dense the plasma was in Voyager's location.
Plasma consists of charged particles and is more prevalent in the extreme cold of interstellar space than in the hot bubble of solar wind that permeates the solar system. Voyager 1, now 21 billion kilometres from earth, could not make the measurement directly because its plasma detector stopped working more than 30 years ago.
"This was basically a lucky gift from the sun," Stone said.