Spiral galaxy NGC 2403. This galaxy lies around 11 million light years from Earth in the constellation Camelopardalis. In 2004 a supernova was seen in this galaxy, the closest to Earth that had been recorded in over a decade. A supernova is the explosive death of a massive star. As the light emission pattern from supernovae is well understood, study of distant supernovae can be used to gauge distances and aid cosmological understanding.