Today is the anniversary of the light from Supernova SN 1987A reaching earth, which occurred on 23 February 1987 (I would have been 4.5 years old). It was officially discovered the next day in both Chile and New Zealand. While it was visible to the naked eye, it could only be seen in the southern hemisphere. It's distance from earth was a measly 51.4 kiloparsecs, or approximately 168,000 light-years. This supernova did not occur in our own Milky Way, however; it was located in the Large Magellanic cloud.
1987A designates it as the first supernova discovered in 1987. It's brightest apparent magnitude was about 2.9 and occurred a couple of months later in May. It slowly faded in the following months. For reference, apparent magitude is a relation made to the star Vega (apparent magnitude 0.0), the fifth brightest star in the sky. It is also logarithmic, and smaller numbers indicate higher brilliance, with the Sun having an apparent magnitude of -27. For comparision there are 171 stars that have an apparent magnitude of 3.0 or better. Thus, you could not see it in the daytime like the most famous of instances, SN 1006.
This event had a Blue supergiant progenitor, which was considered unusual at the time. It was a Type II event, ie, a rapid core collapse of a lone massive star (8 to 40X the mass of the sun). This should have resulted in a neutron star being left over after the event, but so far it has been MIA as it has not been detected. Finally, there are three bright rings around the event area that are pre-existing material from the progenitor star's stellar wind. These rings were actually large enough structures that they were used to calculate the distance to the supernova using trigonometry. It is predicted these rings will fade away between 2020 and 2030 as the structures will be destroyed by the ever expanding shockwave from the supernova event.
Above: remnant seen in light overlays of different spectra.
