M51bs
M51bs is a designation given to a pair of dwarf galaxies that orbit the much larger Whirlpool Galaxy (M51a). These companion galaxies, designated M51bs-1 and M51bs-2, are located approximately 28 million light-years away in the constellation Canes Venatici. They were discovered in 2005 using data from the Hubble Space Telescope.
M51bs-1 and M51bs-2 are significantly smaller and less luminous than the Whirlpool Galaxy. Their gravitational interaction