SN 1987A was a type II supernova in the Large Magellanic Cloud, a dwarf satellite galaxy of the Milky Way. It occurred approximately from Earth and was the closest observed supernova since Kepler's Supernova. 1987A's light reached Earth on February 23, 1987, and as the earliest supernova discovered that year, was labeled "1987A". Its brightness peaked in May, with an apparent magnitude of about 3. It was the first supernova that modern astronomers were able to study in great detail, and its observations have provided much insight into core-collapse supernovae. SN 1987A provided the first opportunity to confirm by direct observation the radioactive source of the energy for visible light emissions, by detecting predicted gamma-ray line radiation from two of its abundant radioactive nuclei. This proved the radioactive nature of the long-duration post-explosion glow of supernovae. For over thirty years, the expected collapsed neutron star could not be found, but in 2019, indirect evidence for its presence was found with the Atacama Large Millimeter Array telescope, with further evidence found in 2021 using the Chandra and NuSTAR X-ray telescopes. Discovery SN 1987A was discovered independently by Ian Shelton and Oscar Duhalde at the Las Campanas Observatory in Chile on February 24, 1987, and within the same 24 hours by Albert Jones in New Zealand. Later investigations found photographs showing the supernova brightening rapidly early on February 23. On March 4–12, 1987, it was observed from space by Astron, the largest ultraviolet space telescope of that time. Progenitor Four days after the event was recorded, the progenitor star was tentatively identified as Sanduleak −69 202 (Sk -69 202), a blue supergiant. After the supernova faded, that identification was definitively confirmed by Sk −69 202 having disappeared. This was an unexpected identification, because models of high mass stellar evolution at the time did not predict that blue supergiants are susceptible to a supernova event. Some models of the progenitor attributed the color to its chemical composition rather than its evolutionary state, particularly the low levels of heavy elements, among other factors. There was some speculation that the star might have merged with a companion star before the supernova. However, it is now widely understood that blue supergiants are natural progenitors of some supernovae, although there is still speculation that the evolution of such stars could require mass loss involving a binary companion. Neutrino emissions Approximately two to three hours before the visible