M51, the Whirlpool

The 51st entry in Charles Messier's catalog is "The Whirlpool," a pair of galaxies in which Lord Rosse first observed spiral structure using his "Leviathan" a huge and ungainly telescope on his estate in Ireland. In this image, you can see sprays of stars pulled away by a recent collision between the two galaxies. The brightest star embedded within the outer spiral arm (near "2 o'clock" in the larger galaxy) is a supernova, an exploding star that appeared in 2014.