Discovered: ultra-elusive, super-energetic neutrinos from far-away galaxy
The breakthrough discovery, published in the journal Nature Physics and hailed as a discovery as significant as that of gravitational waves, will offer a unique view of the cosmos by allowing a new generation of telescopes to shed light on the dark matter believed to make up five-sixths of the universe's matter.
"We believe we've identified the first neutrino from outside our home galaxy, the Milky Way," said CSIRO astrophysicist Dr Phil Edwards, who led the Australian part of the team.
After travelling for billions of years from an extremely distant giant galaxy, with a super-massive black hole at its centre, the neutrinos were captured by the South Pole Neutrino Observatory.
Known as the IceCube detector, this cubic kilometre of Antarctic ice is threaded by sensitive light detectors which catch the extremely brief flashes of light emitted when neutrinos interact with the ice.
"IceCube catches the very highest-energy neutrinos," said Dr Edwards. "They're so rare the team chose to name them after Sesame Street characters; the one we have identified is called Big Bird."
The source of the neutrino burst is a galaxy, prosaically dubbed PKS 1424-418, 9.1 billion light years away (a light year being the distance travelled by light in one year).
"IceCube couldn't pinpoint the arrival direction of the neutrino very accurately," Dr Edwards said, "but it's location was entirely consistent with that galaxy being the origin."
They have no charge, virtually no mass and rarely interact with normal matter. Small wonder then that it's taken decades for an international team of scientists to capture evidence of the universe's most energetic particles, known as neutrinos, from another galaxy.