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A VLBI resolution of the Pleiades distance controversy

Science  29 Aug 2014:
Vol. 345, Issue 6200, pp. 1029-1032
DOI: 10.1126/science.1256101

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Distance score settled for Seven Sisters

Most of us have seen the Pleiades star cluster in the night sky, one of the few groups of physically related stars that are separately visible to the naked eye. In spite of its proximity to us, its distance has been disputed. Melis et al. settle the controversy with astrometric measurements from radio interferometry that reveal a distance of 136.2 parsecs (see the Perspective by Girardi). Other methods yielded similar values, but the trusted astrometry satellite Hipparcos measured only 120.2 parsecs. The new result alleviates the concern that astronomers would need to adjust their stellar evolution models to align with the Hipparcos distance.

Science, this issue p. 1029; see also p. 1001

Abstract

Because of its proximity and its youth, the Pleiades open cluster of stars has been extensively studied and serves as a cornerstone for our understanding of the physical properties of young stars. This role is called into question by the “Pleiades distance controversy,” wherein the cluster distance of 120.2 ± 1.5 parsecs (pc) as measured by the optical space astrometry mission Hipparcos is significantly different from the distance of 133.5 ± 1.2 pc derived with other techniques. We present an absolute trigonometric parallax distance measurement to the Pleiades cluster that uses very long baseline radio interferometry (VLBI). This distance of 136.2 ± 1.2 pc is the most accurate and precise yet presented for the cluster and is incompatible with the Hipparcos distance determination. Our results cement existing astrophysical models for Pleiades-age stars.

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