Neutrino burst solves mystery of COSMIC RAY ORIGINS
Ghostly particles offer a key to the origins of high-energy rays
Astronomers are a step closer to solving the century-old conundrum of where cosmic rays come from, having located the source of a burst of neutrinos, the ghostly sub-atomic particles created at the same time as the rays.
The neutrino burst was detected on 22 September 2017 by the IceCube telescope in Antarctica, and astronomers calculated its rough location in the sky. After a year of follow-up observations, they have pinpointed its origin to a blazar – a galaxy with a rapidly spinning black hole that fires out jets of particles. This particular blazar flared up in visible light around the same time the neutrinos were emitted.
This is only the second time that neutrinos have been detected outside the Solar System and the first time they have been traced back to the centre of another galaxy.
“Neutrinos rarely interact with matter,” says Paul O’Brien, head of Physics and Astronomy at the University of Leicester and a member of the observing team. “To detect them at all from the cosmos is amazing, but to have a possible source identified is a triumph. This result will allow us to study the most distant, powerful energy sources in the Universe in a completely new way.”
Discovered in 1910, cosmic rays are particles with enough energy to travel between galaxies. Unfortunately, discovering what creates such energetic particles has been difficult as the rays’ flight is deflected by the magnetic fields they meet along the way. This means the direction in which they arrive at Earth doesn’t necessarily point back to where they were created.
But cosmic rays are not born alone: when they are created, neutrinos form alongside them. As neutrinos have no charge, they are unaffected by magnetic fields and so astronomers can follow their path to discover where they came from.
“This event – the first time we’ve been able to associate light with the source of a high-energy neutrino – occurred less than five weeks after the first joint detection of light and gravitational waves,” says Phil Evans, the development scientist for Swift, a telescope that followed up the detection. “We truly are entering the era of multi-messenger astronomy.”
The IceCube telescope in Antarctica has found a clue to the origins of cosmic rays