Limits on the neutrino magnetic moment from SN1987A.
A neutrino magnetic moment greater than 10/sup -12/..mu../sub B/, the Bohr magneton, would have important implications for gravitational-collapse supernovae. Also, it has been suggested that ..mu../..mu../sub B/approx.10/sup -10/ might solve the solar neutrino problem. However, we show that the neutrino observations of SN1987A and general optical observations of supernovae set a firm upper limit of ..mu../..mu../sub B/<5 x 10/sup -13/. This limit is about 100 times better than the best experimental determination and previous astrophysical limits, and 10--20 times better than a previous limit based on big-bang nucleosynthesis.