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| A Hubble Space Telescope (HST) image of NGC 2403 Credit: HST/NASA/ESA. |
NGC 2403 (also Caldwell 7) is an intermediate spiral galaxy in the constellation Camelopardalis. NGC 2403 is an outlying member of the M81 Group, and is approximately 8 million light-years distant. It bears a striking similarity to M33, being about 50,000 light years in diameter and containing numerous star-forming H II regions. The northern spiral arm connects it to nearby galaxy NGC 2404. NGC 2403 can be observed using 10×50 binoculars.
NGC 2403 was discovered by William Herschel in 1788. Allan Sandage detected Cepheid variables in NGC 2403 using the Hale telescope, giving it the distinction of being the first galaxy beyond our local group within which a Cepheid was discovered.[2] He derived a distance of a mere 8 thousand light years.[2] Today, it is thought to be a thousand times further away at about 8 million light years (2.5 Mpc).