The SuperNova Early Warning System (SNEWS) is a network of neutrino detectors designed to give early warning to astronomers in the event of a supernova in the Milky Way Galaxy, our home galaxy, or a nearby galaxy such as the Large Magellanic Cloud or the Canis Major Dwarf Galaxy. Enormous numbers of neutrinos are produced in the core of a red giantstar as it collapses on itself. In the current model the neutrinos are emitted well before the light from the supernova peaks, so in principle neutrino detectors could give advance warning to astronomers that a supernova has occurred and may soon be visible. The neutrino pulse from supernova 1987A arrived 3 hours before the associated photons – but SNEWS was not yet active and it was not recognised as a supernova event until after the photons arrived.
The detectors will send reports of a possible supernova to a computer at Brookhaven National Laboratory, Long Island. New York to identify a supernova. If the SNEWS computer identifies signals from two detectors within 10 seconds, the computer sends a supernova alert to observatories around the world to study the supernova.