Spiral galaxy NGC 2403. This galaxy consists of a central nucleus surrounded by spiral arms. It also hosts a supernova that was discovered in 2004 (orange star directly left of the galaxy's nucleus). A supernova is the explosive death of a massive star and this one is the closest to Earth that had been recorded in over a decade. As the light emission pattern from supernovae is well understood, study of distant supernovae can be used to gauge distances and aid cosmological understanding. NGC 2403 lies about 12 million light years from Earth, in the constellation Camelopardalis.