Open star cluster NGC 2477. True-colour optical image of the open star cluster NGC 2477 (upper centre) in the constellation Puppis. NGC 2477 contains around 300 stars, and is very dense for an open cluster. It was only distinguished from a globular cluster by spectroscopic methods. Globular clusters contain very old stars, whereas the stars in NGC 2477, as in all other open clusters, are very young. All open clusters are thought to contain stars which formed together from the same cloud of gas and dust. The blue star just below NGC 2477 is b Puppis. This image was produced by digitally combining photographs taken by the UK Schmidt Telescope in blue and red light.