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A distance of 133–137 parsecs to the Pleiades star cluster


Nearby ‘open’ clusters of stars (those that are not gravitationally bound) have played a crucial role in the development of stellar astronomy because, as a consequence of the stars having a common age, they provide excellent natural laboratories to test theoretical stellar models. Clusters also play a fundamental part in determining distance scales. The satellite Hipparcos1 surprisingly found that an extensively studied open cluster—the Pleiades (also known as the Seven Sisters)—had a distance of D = 118 ± 4 pc (refs 2, 3), about ten per cent smaller than the accepted value4,5,6. The discrepancy generated a spirited debate because the implication7 was that either current stellar models were incorrect by a surprising amount or Hipparcos was giving incorrect distances. Here we report the orbital parameters of the bright double star Atlas in the Pleiades, using long-baseline optical/infrared interferometry. From the data we derive a firm lower bound of D > 127 pc, with the most likely range being 133 < D < 137 pc. Our result reaffirms the fidelity of current stellar models.

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We thank other members of the PTI and Mark III teams and especially A. Boden and B. Lane for a careful reading. We gratefully acknowledge discussions with N. Reid, R. M. Rich, D. Sasselov, J. Stauffer, J. Tomkin and D. VandenBerg. We extensively used the SIMBAD database of astronomical papers and are grateful to CDS, France, and NASA for maintaining this system. The research described in this paper was primarily carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. S.R.K.'s research is supported by NSF and NASA.

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Correspondence to S. R. Kulkarni.

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Figure 1: Fringe visibilities and model fits for Atlas.
Figure 2: The visual orbit of Atlas.
Figure 3: Mass–distance relationship for Atlas.


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