Discovered by William Herschel in 1788.
NGC 2403 is a member of the M81 group of galaxies located in the constellation Camelopardalis at an estimated distance of from 8 to 10 million light-years from the Earth. This classic spiral galaxy is noted for its abundant star forming HII regions. A portion of NGC 2403ís large HII regions are comparable to the most massive star forming nebulae in the Large Magellenic Cloud and NGC 604 in M33. Such areas are referred to as Giant HII regions. NGC 2403 possess at least six of these colossal HII regions.