APOD 2.2-Historical Supernova Remnant

In the year 185 AD the appearance of a new star, Nanmen asterism, was noted by some Chinese astronomers. This star was visible for months and is believed to be the earliest recorded supernova in history. This picture is a false-color view that shows interstellar gas heated by the expanding supernova. This supernova, RCW 86, is understood to be the remnant of a stellar explosion. This is a Type Ia supernova which means there are thermal explosions that destroy a white dwarf star as it accreates material from a companion in a binary star system, whatever that means. ert. RCW 86 is about 8,200 light-years away and has an estimated radius of 50 light-years!