In a supernova event about 1053 erg of gravitational binding energy are released, the bulk of which is carried off by neutrinos. The neutrino burst detected in February 1987 recorded a supernova explosion that took place in the Large Magellanic Cloud some 50 kpc away from the earth and confirmed the basics of models of stellar collapse. Indeed, the neutrino luminosity inferred from observation agrees with the luminosity predicted by detailed model calculations of neutrino transport. However, there is some room (within the uncertainties of both theory and observation) for extra exotic sources of energy drain. Among them, there are right-handed neutrinos, which appear in almost any extension of the minimal standard model of electroweak interactions. In particular, if neutrinos are massive Dirac particles, the right-handed degrees of freedom should be copiously emitted in a supernova collapse. Using SN1987A data one can place bounds on neutrino masses or on the magnetic moment of the neutrino. Furthermore, independently of the energetics of stellar dynamics, the actual detection of neutrinos at IMB and Kamioka has led to relevant limits on neutrino mass, neutrino lifetime, and neutrino charge. © 1992.