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 , 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 supernova reached Earth on February 23, 1987. As 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.
It was discovered by Ian Shelton and Oscar Duhalde at the Las Campanas Observatory in Chile on February 24 1987, and independently by Albert Jones in New Zealand, and Colin Henshaw (member of the Manchester Astronomical Society) in Zimbabwe. On March 4-12, 1987 it was observed from space by Astron, the largest ultraviolet space telescope of that time.
Since 51.4 kiloparsecs is approximately 168,000 light-years, the cosmic event itself happened approximately 168,000 years prior to its observation in 1987.
Most supernovas grow dimmer with the passage of time as they release their energy. But the X-ray and radio emissions from 1987A grew brighter because its shock wave had crashed into a dense cloud of gas and dust.
There were 3 neutrino bursts observed. The Mont Blanc computer detected a burst of five pulses about 8 hrs before the first optical observation, followed by a second burst of three pulses about 2 hrs later; Kamioka and Baksan reported observations of a burst made by eleven and five pulses, respectively, delayed by 4.7 hrs in comparison with the Mont Blanc burst. (Refer http://adsabs.harvard.edu/abs/1989NYASA.571..584A)
Approximately three hours before the visible light from SN 1987A reached the Earth, a burst of neutrinos was observed at three separate neutrino observatories. This is due to the neutrino emission (which occurs simultaneously with core collapse) preceding the emission of visible light (which occurs only after the shock wave reaches the stellar surface). At 7:35am Universal time, Kamiokande II detected 11 antineutrinos, IMB 8 antineutrinos and Baksan 5 neutrinos, in a burst lasting less than 13 seconds. Water-based instruments detect only antineutrinos of thermal origin, while a gallium-71-based instrument detects only neutrinos (lepton number = +1) of either thermal or electron-capture origin.
Although the actual neutrino count was only 24, it was a significant rise from the previously-observed background level. This was the first time neutrinos emitted from a supernova had been observed directly, and the observations were consistent with theoretical supernova models in which 99% of the energy of the collapse is radiated away in neutrinos. The observations are also consistent with the models' estimates of a total neutrino count of with a total energy of joules.
One highly significant result was obtained from the data regarding gravity. It appeared that the neutrinos and antineutrinos both took the same amount of time to arrive at earth, about 168,000 years. The difference in their arrival times was less than 12 seconds. This was the first empirical evidence that matter, antimatter, and photons all react similarly to gravity, which had been widely predicted by standard theories of gravity but had not been previously shown from direct empirical data.