APOD: 2022 May 28 - RCW 86: Historical Supernova Remnant

Good afternoon, Rallypoint, and welcome to the May 28th edition of Astronomy Picture of the Day (APOD): "RCW 86: Historical Supernova Remnant." If you've been following APOD for a while, you likely remember that the closest star to Earth, Alpha Centauri (α Cen) is found in the constellation Centaurus (the Centaur). Second-century BC Chinese astronomers had another name for this asterism: the Nán Mén, or Southern Gate. In 185 BC, they recorded the appearance of a new star that faded after several months. It is believe to be the first recorded observation of a supernova.

Today's APOD shows us what is left of that explosion. Because there is no evidence of a neutron star or pulsar, scientists believe this was a Type 1a supernova: a thermonuclear detonation of a white dwarf star that had become unstable through accretion of sufficient mass from a companion binary star. RCW 86 is about 100 light years across and lies 8,000 light years from Earth.