How did Galileo’s observations change knowledge of the Pleiades?
Most of the brightest stars are older yellow stars, but a few young blue stars are also visible. This picture is a composite of three images taken by the Hubble Space Telescope.
Before Galileo turned his telescope toward the Pleiades, the cluster was known primarily for the six or seven stars visible to the unaided eye, which held significant roles in global mythology and cultural calendars.1
Galileo’s telescopic observations fundamentally changed the understanding of the group by revealing that it was far more populous than previously thought. He discovered that the cluster contained more than 40 individual stars, demonstrating that the Pleiades was a dense collection of celestial objects rather than just the small grouping visible to the naked eye.1