A celestial object known as a blazar is a source of high-energy neutrinos, report two new studies. Neutrinos are light particles that only weakly interact with ordinary matter. Just two individual sources of astrophysical neutrinos were previously known (the Sun and a nearby supernova), with no new sources discovered for 30 years. In 2013, researchers analyzing data from the IceCube Neutrino Observatory near the South Pole in Antarctica discovered higher-energy astrophysical neutrinos and have been seeking their sources ever since. Now, the IceCube Collaboration reports the detection of a high-energy neutrino event whose arrival direction was consistent with a known blazar, a type of quasar in which material falling into a supermassive black hole produces a jet oriented directly along the line of sight to Earth. In the first of the papers, they describe the detection and team up with numerous groups of astronomers to perform so-called multi-messenger astronomy - observing the same object in light and neutrinos. The blazar, TXS 0506+056, was found to be in a "flaring state" when the neutrino signal arrived in September 2017, with bright emission across multiple wavelengths. Observations were performed across the electromagnetic spectrum, from radio waves to gamma rays. Motivated by this discovery, a separate report from the IceCube Collaboration searched the records of neutrinos detected by IceCube over nearly ten years before the 2017 flare, finding an excess of neutrino events at the location of the TXS 0506+056 blazar, showing it has produced neutrinos in multiple bursts. Taken together, these studies demonstrate that high-energy neutrinos are produced by this blazar, establishing a new field of multi-messenger neutrino astrophysics.
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Journal
Science