Messier 45 (Pleiades)
Messier object number 45 (NGC 1432) is an open cluster and diffuse nebula in the constellation of Bull. It is also known as the Pleiades. It is approximately 444 lightyears away from earth.
Long before the telescope had been invented, the Pleyades were known as a star formation already to the ancient Greek. This very distinct star formation, which is easily visible with the naked eye, was also known in many other ancient cultures. It is a star formation area, so all of its stars are very young. On long exposed photographs, a faint gas nebula is visible around these stars. It is the remnant of the gas from which these stars were formed.