The Double Cluster

About This Photograph

Here is a close-up of two open star clusters in the constellation of Perseus, together known as the Double Cluster. Open clusters form when giant molecular clouds of gas and dust collapse under their own gravity. For a time, this gives rise to stellar nurseries such as M78, NGC 1333, and the Orion Nebula. Once the stars have formed, they eventually erode the remains of the cloud and are left floating freely in space.

These two clusters, known individually as NGC 884 (upper left) and NGC 869 (lower right) formed at roughly the same time around 12.8 million years ago. They both contain a rich collection of bright blue-white super-giant stars. NGC 884 also contains five prominent red super-giant stars. These clusters are visible with the naked eye, and make a beautiful sight through binoculars and small telescopes.

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