M45

The Pleiades is the most famous of all open star clusters, containing around 500 members set against a black velvet sky. This young first magnitude open cluster is easily visible to the unaided eye and resembles a smaller version of the Big Dipper. At least 6 hot blue stars are readily visible and keen eyed observers can see more. Because of its large diameter, 2 degrees, M45 is best seen in binoculars. A faint veil of nebulosity surrounds the brightest Pleiades members, with the most easily observable patch being the Merope Nebula (IC 349), which surrounds the star Merope. These reflection nebulae are not remnants of the gas cloud where the Pleiades was born, but a chance cloud of dust that the cluster is passing through. In some ancient cultures, ceremonies to honour the dead were held on the day when the Pleiades reached its highest point in the sky at midnight (this is around Hallowe'en). Ancient Aztecs believed the Pleiades would be overhead at midnight the day the world ended.