The Whirlpool Galaxy (also known as Messier Object 51, Messier 51, M51 or NGC 5194 or Whirlpool Galaxy) is a spiral galaxy located in the constellation Canes Venatici (hunting dog) Classic. It was discovered by Charles Messier on October 13, 1773. It is one of the most famous spiral galaxies in the sky.
This image of a pair of interacting galaxies called Arp 273 was released to celebrate the 21st anniversary of the launch of the NASA/ESA Hubble Space Telescope. The distorted shape of the larger of the two galaxies shows signs of tidal interactions with the smaller of the two. It is thought that the smaller galaxy has actually passed through the larger one