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How old is the Pleiades star cluster?

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Centre of star cluster 47 Tucanae (NGC 104), showing the colours of various stars.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. — Star cluster Centre of star cluster 47 Tucanae (NGC 104), showing the colours of various stars.
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.

The Pleiades star cluster is approximately 100 million years old.12

As an open cluster, the Pleiades is considered relatively young. Astronomers estimate its age by analyzing its colour-magnitude diagram; the brightest stars in the cluster have begun to exhaust the hydrogen in their cores and are currently leaving the main sequence, a process that indicates the cluster's approximate age.1