These two famous galaxies, M66 and M65, are close to each other, both in our sky and in their own environment. They make a beautiful photographic pair. This isn’t all that great a shot of them, but it was made to capture a supernova in M65, visible as the bright star below the nucleus of the galaxy, the left one in this image. This is very likely an important supernova, as the distance to M65 has been relatively precisely determined. Given a known distance, the absolute brightness of the supernova can be calculated, and used to calibrate the brightness of other supernovae in other galaxies. This makes it possible to determine more precise distances to any galaxy in which this type of supernova appears.