M45

The Pleiades (also known as the Seven Sisters or Subaru) is one of the nearest and most obvious open star clusters in the sky, located about 444 light-years away in Taurus. The cluster contains over 1,000 stars, though only six to seven are easily visible to the naked eye. The brightest members are hot blue B-type stars that formed together roughly 100 million years ago. The cluster is currently passing through an unrelated dust cloud, creating the famous blue reflection nebulosity visible in photographs.

Best viewed with the naked eye or binoculars rather than a telescope — the cluster spans about 2 degrees (four full Moon widths), which overfills most telescope eyepieces. The naked eye typically reveals 6-7 stars; keen-eyed observers from dark sites may count 10-14. Binoculars (7x50 or 10x50) frame the cluster perfectly and reveal dozens of fainter members cascading between the bright stars. Long-exposure photographs reveal the blue reflection nebulae around the brightest stars, but these are extremely difficult visually, requiring excellent skies and a large aperture. Best observed from October through March.

Known since prehistory and referenced in the writings of Homer, Hesiod, and the Bible (Book of Job). The name 'Pleiades' comes from Greek mythology — the seven daughters of Atlas and Pleione. Nearly every culture worldwide has myths about this cluster. Galileo was the first to observe the cluster telescopically in 1610, revealing many more stars than visible to the naked eye. The Japanese name 'Subaru' is now famous as the car manufacturer's logo, which depicts the cluster.