Barnard's galaxy
The galaxy is famous because it is where cepheid variables were used to find out how far away the galaxy was. Edwin Hubble found 11 cepheid variable stars, and used them to find the distance to the galaxy. This settled a great debate in the 1920s about the scale of the universe and the nature of spiral galaxies. It became clear that all "spiral nebulae" were in fact spiral galaxies. They are far outside our own Milky Way.