SICARDY, B.; BELLUCCI, A.; GENDRON, E.; LACOMBE, F.; LACOUR, S.; LECACHEUX, J.; LELLOUCH, E.; RENNER, S.; PAU, S.; ROQUES, F.; LE CAMPION, J.-F.

doi:10.1038/nature04351

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SICARDY, B.
Laboratoire d'études spatiales et d'instrumentation en astrophysique [LESIA]

BELLUCCI, A.
Laboratoire d'études spatiales et d'instrumentation en astrophysique [LESIA]

GENDRON, E.
Laboratoire d'études spatiales et d'instrumentation en astrophysique [LESIA]

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Nature. 2006, vol. 439, Issue 7072, p. 52-54

Nature Publishing Group

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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 arcsec) on the sky. One occultation (in 1980) yielded a lower limit of 600km for the satellite's radius, which was later refined to 601.5km (ref. 4). Here we report observations from a multi-station stellar occultation by Charon, which we use to derive a radius, RC = 603.6 +/- 1.4km (1sigma), and a density of rho = 1.71 +/- 0.08gcm-3. This occultation also provides upper limits of 110 and 15 (3sigma) nanobar for an atmosphere around Charon, assuming respectively a pure nitrogen or pure methane atmosphere.< Réduire

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

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