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The Pinwheel Galaxy (also known as Messier 101 or NGC 5457) is a face-on spiral galaxy about 27...

The Pinwheel Galaxy (also known as Messier 101 or NGC 5457) is a face-on spiral galaxy about 27 million light-years away in the constellation Ursa Major. It was discovered by Pierre Méchain on March 27, 1781, and he subsequently communicated his discovery to Charles Messier who verified its position and added it to the Messier Catalogue as one of the final entries. On February 28, 2006, NASA and the ESA released a very detailed image of Pinwheel Galaxy, which was the largest and most detailed image of a galaxy by Hubble Space Telescope at the time. The image was composed from 51 individual exposures, plus some extra ground-based photos. Pierre Méchain, the discoverer of M101, described it as a "nebula without star, very obscure and pretty large, 6' to 7' in diameter, between the left hand of Bootes and the tail of the great Bear. It is difficult to distinguish when one lits the [grating] wires." William Herschel noted in 1784 that "[M101] in my 7, 10, and 20-feet reflectors shewed a mottled kind of nebulosity, which I shall call resolvable; so that I expect my present telescope will, perhaps, render the stars visible of which I suppose them to be composed." Lord Rosse observed M101