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 Hipparcos(1) 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 value(4-6). The discrepancy generated a spirited debate because the implication(7) 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.