SN 1987A was a
supernova in the outskirts of the
Tarantula Nebula in the
Large Magellanic Cloud (a nearby
dwarf galaxy). It occurred approximately 51.4
kiloparsecs from
Earth, approximately 168,000
light-years, close enough that it was visible to the
naked eye. It could be seen from the Southern Hemisphere. It was the closest observed supernova since SN 1604, which occurred in the
Milky Way itself. The light from the new supernova reached Earth on February 23, 1987. As it was the first supernova discovered in 1987, it was labeled “1987A”. Its brightness peaked in May with an
apparent magnitude of about 3 and slowly declined in the following months. It was the first opportunity for modern
astronomers to see a supernova up close and observations have provided much insight into
core-collapse supernovae. Of special importance, SN1987A provided the first chance to confirm by direct observation the radioactive source of the energy for visible light emissions by detection of predicted gamma-ray line radiation from two of its abundant radioactive nuclei,
56Co and
57Co. This proved the radioactive nature of the long-duration post-explosion glow of supernovae.