  The detection of neutrinos from SN1987A confirmed the core-collapse nature of
SN II, but the neutrinos were not noticed until after the optical discovery.
The current generation of neutrino experiments are both much larger and
actively looking for SN neutrinos in real time. Since neutrinos escape a new SN
promptly while the first photons are not produced until the photospheric shock
breakout hours later, these experiments can provide an early warning of a
coming galactic SN II. A coincidence network between neutrino experiments has
been established to minimize response time, eliminate experimental false
alarms, and possibly provide some pointing to the impending event from neutrino
wave-front timing.
