SN 1987A: The Last Nearby Supernova (1987)
A blue supergiant in the Large Magellanic Cloud exploded 168,000 light-years from Earth—the closest supernova since Kepler's in 1604. Neutrino detectors in Japan and the US captured about two dozen particles from the collapsing core, confirming decades of theoretical predictions about supernova physics.
The 19 detected neutrinos proved that core collapse releases most energy as neutrinos, not light. The star's unusual blue color challenged supernova models.
SN 1987A established neutrino astronomy as a field and motivated construction of larger detectors like Super-Kamiokande, which could detect neutrinos from a failed supernova within our galaxy.
A failed supernova would produce a neutrino burst without the optical supernova. Detecting such a signal would provide smoking-gun evidence. Current detectors could catch a galactic failed supernova, but M31-2014-DS1 at 2.5 million light-years is too distant.