Controversy reignites over distance of Pleiades star cluster

New measurement points to possible error in ESA survey that could also affect the agency's new Gaia mission. The most precise measurement yet of the distance to the Pleiades star cluster is reviving a dispute that has split the astronomy community largely down a trans-Atlantic divide for the past 17 years. The latest result, from a US team using a worldwide network of radio telescopes, is in good agreement with more than a dozen previous measurements to the Pleiades, made using multiple techniques. But it stands in sharp contrast to a figure from the Hipparcos satellite of the European Space Agency (ESA). The authors of the latest study, published today in Science, say they believe that the Hipparcos measurement is an error, and worry that the same problem could affect its successor mission, ESA's Gaia space telescope, which began taking data last month. The alternative is even less appealing: if Hipparcos is right, then accepted theories of the physics of stars could require some mending.