Skywatch

  • November 23, 2006

    Episode 69: Stellar Sorting

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    Globular clusters, groups of hundreds of thousands of stars held together by gravity, formed in the early universe. Astronomers have predicted that, due to the force of gravity over millions of years, the most massive stars would migrate to the center of the cluster, while the "lighter" stars would drift to the outer parts. The Hubble Space Telescope recently discovered evidence that this theory was true by measuring the speed of stars in 47 Tucanae - one of the densest globular clusters in the Southern hemisphere.