- M 101 The Pinwheel Galaxy
M 101 (NGC 5457) is a large, beautiful spiral galaxy in the constellation Ursa Major. We see this galaxy almost face-on. The shape of the galaxy is somewhat asymmetric, with the lower arm exhibiting a distinct "kink" about midway through it. This is likely the result of an interaction with another nearby galaxy— M 101 has several small satellite galaxies in its immediate vicinity. M 101 lies at a distance of around 21.8 million LY and has a diameter estimated to be 184,000 LY— almost twice the size as our Milky Way Galaxy. The delicate spiral arms of this galaxy are studded with bright, pinkish HII regions where new stars are being formed. The outer portions of the arms also have a somewhat bluish tinge due to the presence of numerous young blue-white stars.
M 101 was discoved by Messier's colleague Pierre Mechain in March 1781. It was one of the last objects included in Messier's original list prior to its publication. M 101 has a visual magnitude of 7.7 and is easily visible in binoculars or a small telescope. A large telescope reveals the beautiful spiral structure of it.
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