Powerful bursts of
electron neutrinos (νe) with typical energies of the order of 10 MeV and duration of the order of 10 seconds are produced in the
core of a
red giant star as it collapses on itself via the "neutronization" reaction, i.e. fusion of protons and electrons into neutrons and neutrinos: p + e− → n + νe. It is expected that the neutrinos are emitted well before the light from the supernova peaks, so in principle neutrino detectors could give 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. Directional precision of approximately 5° is expected. SNEWS is not able to give warning of a
Type Ia supernova, as they are not expected to produce significant numbers of neutrinos. Type Ia supernovae, caused by a runaway nuclear fusion reaction in a
white dwarf star, are thought to account for roughly one-third of all supernovae. There are currently seven neutrino detector members of SNEWS:
Borexino,
Daya Bay,
KamLAND,
HALO,
IceCube,
LVD, and
Super-Kamiokande. SNEWS began operation prior to 2004, with three members (Super-Kamiokande, LVD, and SNO). The
Sudbury Neutrino Observatory is no longer active as it is being upgraded to its successor program
SNO+. The detectors send reports of a possible supernova to a computer at
Brookhaven National Laboratory to identify a supernova. If the SNEWS computer identifies signals from two detectors within 10 seconds, the computer will send a supernova alert to observatories around the world to study the supernova. The SNEWS mailing list is open-subscription, and the general public is allowed to sign up; however, the SNEWS collaboration encourages amateur astronomers to instead use
Sky and Telescope magazine's AstroAlert service, which is linked to SNEWS. == See also ==