https://github.com/davepinch/pinchy.cc/blob/master/content/fragments/if-math-defines-reality-than-you-are-defined-in-math.md
The June issue of Sky and Telescope contains a short reference to the discovery of a supernova in N.G.C. 5195, a satellite of the famous Whirlpool galaxy M51. M. L. Humason was observing this satellite for the first time in three years, and on April 6 [of 1945] he noticed a faint star with which he was not previously familiar. The following evening he obtained its spectrum, which confirmed his suspicions that it was a supernova. At the time of discovery it had passed maximum by about 65 days. On April 12 the nova was at magnitude 16 photographic and 14 photovisual ; its estimated maximum brightness was 11:0 photographic. It was fortunate that Humason had M 51 down on his observing programme on April 6, because the star was fading so rapidly that in a few weeks it would probably have been overlooked. A supernova appears in a spiral nebula on an average once in four hundred years, and this makes the coincidence all the more remarkable. In addition, the star would probably have escaped detection if it had not been so close to the central nucleus.