A ghostly particle was captured in a patch of ice beneath the South Pole in September of last year by the IceCube Antarctic detector—the orbiting Fermi Gammaray Space Telescope. Astronomers believe that this particle—a neutrino, electrically neutral and almost massless—likely came for a far off blazar, a hugely bright source of radiation powered by a supermassive black hole. The new finding could mark the founding event of neutrino astronomy, writes Daniel Clery in Science.
These particles are known as ultrahigh-energy cosmic rays because they exude a million times more energy than those produced in earthbound particle accelerators. Astronomers have yet to unequivocally pinpoint the source that boosts these particles to massive energies, but have speculated that it could be neutron stars, gamma ray bursts, hypernovae, or radiation-spewing black holes. However, they believe that whatever the source, high energy neutrinos are a likely byproduct. The IceCube neutrino detector captures these elusive particles in a cubic kilometer of Antarctic ice. Based on the location, timing, and brightness of the detected light, researchers can reconstruct the path and energy of the neutrino.
Last September’s ensnared neutrino, called IceCube-170922A, is calculated to have an energy of 290 TeV, and has offered scientists a clear track back into space. Six days after the observation, the Fermi team reported the satellite discovered a blazar, called TXS 0506+056, was especially bright, having started to flare, and less than 0.1° away from the neutrino’s path. Blazars are distant cosmic beacons powered by supermassive black holes that fire jets of particles from their poles. Though it’s not clear whether TXS 0506+056 was flaring when IceCube-170922A started its journey to Earth, Pierre Sokolsky of the University of Utah in Salt Lake City has hope, saying “it’s a very mouthwatering observation and I very much hope it will be confirmed.”