Star Clusters

An entire family with the same birthday?

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Science  16 Jan 2015:
Vol. 347, Issue 6219, pp. 245
DOI: 10.1126/science.347.6219.245-e

Astronomers often read the history of a star cluster in the shapes that emerge when its members are plotted in color-magnitude space. Tight curves suggest a population with very similar ages, whereas more extended features imply a broader range of ages. Li et al. consider the main-sequence turn-off—where stars have exhausted hydrogen in their cores—for the massive cluster NGC 1651 and demonstrate the feature's breadth with plots of Hubble Space Telescope photometry. Surprisingly, their models show that the spread can be manifested only if the population shares one common age. Five other massive clusters show the same phenomenon, which the authors interpret as evidence of populations composed of rapidly rotating stars, which should revise interpretations of color-magnitude diagrams.

Nature 10.1038/nature13969 (2014).

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