It is one of the most famous galaxies in the sky. The galaxy and its companion (NGC 5195) are easily observed by amateur astronomers, and the two galaxies may even be seen with binoculars. The Whirlpool Galaxy is also a popular target for professional astronomers, who study it to further understand galaxy structure (particularly structure associated with the spiral arms) and galaxy interactions.
What was later known as the Whirlpool Galaxy was discovered on October 13, 1773 by Charles Messier, and is designated as M51. Its companion galaxy, NGC 5195, was discovered in 1781 by Pierre Méchain.
Located within the constellation Canes Venatici, M51 is found by following the easternmost star of the Big Dipper, Eta Ursae Majoris, and going 3.5° southeast. Its declination is +47°, making it a circumpolar for observers located above 43°N latitude; it reaches high altitudes throughout the northern hemisphere making it an accessible object from the early hours in winter through the end of spring season, after which observation is hindered in lower latitudes.