Supernovae in Our Neighborhood

Abstract

Prior to 1885 and the discovery by Gully, Ward, and Hartwig of a supernova in the Andromeda Galaxy (also known as Messier 31 or NGC 224), the only supernovae observed by human beings were ones within our own Milky Way Galaxy. This is hardly surprising as supernovae in external galaxies could not be discovered prior to the availability of powerful telescopes, and the true nature of them did not become apparent until the 20th century. With absolute magnitudes in the range of −19 to −20 for Type Ia events and, typically, −17 for Type IIs, it is not hard to work out that a supernova within our own galaxy can easily be a naked-eye object. If an object has an absolute magnitude of −19 (i.e., a magnitude of −19 at a distance of 32.6 light-years), then even across a distance of 3,260 light-years it will have a magnitude of −9 (i.e., 100 times brighter than the planet Venus). A supernova within a few hundred light-years of the earth would turn night into day as it would shine brighter than the full moon, but with all of the light radiating from a point source.