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The Whirlpool Galaxy (also known as Spiral Galaxy M51, Messier Object 51, Messier 51, M51, or NGC 5194) is a classic spiral galaxy located in the Canes Venatici constellation. It was discovered by Charles Messier on October 13, 1773.
The Whirpool Galaxy is one of the brightest, most compelling galaxies in the sky, visible with binoculars. The spiral galactic structure was first observed in this galaxy, which is the dominant member of the M51 group of galaxies .
Its companion galaxy, NGC 5195, was discovered in 1781 by Pierre Méchain. Sometimes M51 is used to refer to the pair of galaxies, in which case the individual galaxies may be referred to as M51A (5194) and M51B (5195). The galaxy is less than 37 million light years away from Earth — some measurements put the distance at only 15 million.