Charon's size and an upper limit on its atmosphere from a stellar occultation

  title={Charon's size and an upper limit on its atmosphere from a stellar occultation},
  author={B. Sicardy and A. Bellucci and E. Gendron and F. Lacombe and S. Lacour and J. Lecacheux and E. Lellouch and S. Renner and S. Pau and F. Roques and T. Widemann and F. Colas and F. Vachier and R. V. Martins and N. Ageorges and O. Hainaut and O. Marco and W. Beisker and E. Hummel and C. Feinstein and H. Levato and A. Maury and E. Frappa and B. Gaillard and M. Lavayssi{\`e}re and M. D. Sora and F. Mallia and G. Masi and R. Behrend and F. Carrier and O. Mousis and P. Rousselot and A. Alvarez-candal and D. Lazzaro and C. Veiga and A. Andrei and M. Assafin and D. D. S. Neto and C. Jacques and E. Pimentel and D. Weaver and J. Lecampion and F. Doncel and T. Momiyama and G. Tancredi},
Pluto and its satellite, Charon (discovered in 1978; ref. 1), appear to form a double planet, rather than a hierarchical planet/satellite couple. Charon is about half Pluto's size and about one-eighth its mass. The precise radii of Pluto and Charon have remained uncertain, leading to large uncertainties on their densities. Although stellar occultations by Charon are in principle a powerful way of measuring its size, they are rare, as the satellite subtends less than 0.3 microradians (0.06… Expand

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