Winnecke 4

Messier 40, also known as Winnecke 4, is one of the more curious entries in Charles Messier's catalogue: rather than a nebula or cluster it is simply a close pair of unrelated stars in Ursa Major. Messier recorded it in 1764 while looking for a nebula reported near this position, noting only two faint stars. It has been kept on the list ever since as a historical oddity. The two stars shine at roughly 9th magnitude and are an easy split in a small telescope.