Brightest open star cluster

The brightest open cluster in the sky is the Pleiades (M45), also known as the Seven Sisters. Located in the constellation of Taurus (The Bull), the Pleiades contains around 500 individual stars in a region of space around 20 light years across, and at an average distance of around 380 light years. Even from within a major light-polluted city, around six of the Pleiades can be seen with the naked eye. These stars are young (astronomically speaking), with ages of around 75 million years, compared to the 4,600-million-year age for the Sun. Many of the brighter stars are still surrounded by dusty nebulae – the leftover material from which they formed.

The brightest star in the Pleiades is Alcyone, with an apparent magnitude of 2.87.