Let there be light: 'ghost' particle found a mile beneath Antarctica holds key to breakthrough in physics
The secrets of the origins of light are set to be unlocked by the discovery of an elusive “ghost” particle a mile beneath Antarctica, scientists have announced. Astronomers have for the first time identified the source of a high-energy neutrino which shot through a solid ice laboratory at the South Pole last year in a “triumph” that promises to revolutionise understanding of fundamental physics. Neutrinos are virtually massless, subatomic particles which race across the universe, passing unnoticed through planets and stars. Despite their abundance - hundreds of billions pass through each human every second - they have so far proved impossible to detect because they interact with matter so rarely. However, the detection of a neutrino on September 22 2017 has since enabled scientists to identify its point of origin using a complex network of ground and space-based radiation telescopes. The international team traced the particle’s provenance to a flaring galaxy, or “blazar”, with a supermassive black hole at its heart four billion light years away. Because the neutrino comes from such a powerful light-producing source, its discovery should allow scientists to begin investigating the precise mechanism through which light is formed. Published in the journal Science, the breakthrough is being hailed as equal in importance to the discovery of gravitational waves - “ripples” in space-time - in 2015. Professor Paul O’Brien, who contributed to the study at the University of Leicester, said: “This result will allow us to study the most distant, powerful energy sources in the universe in a completely new way. He added: “This includes the energy that goes into making light.” Together with gravitational waves, the awareness of high-energy neutrinos gives astronomers a third “messenger” through which to understand space, having until recently relied mainly on visual observations. Professor O’Brien likened it to a person who for years relied on just one physical sense to engage with the world suddenly having three. France Cordova, director of the US National Science Foundation (NSF) that manages the IceCube laboratory where the particle was captured, said: "The era of multi-messenger astrophysics is here.” The IceCube laboratory detected the neutrino in September 2017 Credit: PA The laboratory encompasses more than a cubic kilometre of deep, pristine ice, that detects neutrinos through their secondary particles, muons, which are produced on the rare occasion that a neutron interacts with matter in the vicinity of the detector. The kilometres-long “tracks” that are produced allow astronomers to calculate which direction a particle came from. “There have been previous claims that blazar flares were associated with the production of neutrinos, but this, the first confirmation, is absolutely fundamental,” said Carlo Ferrigno from the University of Geneva. “This is an exciting period for astrophysics.” Other types of neutrino arrive at Earth from the Sun, but these are less high-powered and therefore less instructive as to the origins of light.