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Occultation by Charon. 2005 C313.2. Observed by 4 MIT–Williams teams on 5 telescopes: Pico dos Dias (Brazil) – clouded out (Jay Pasachoff and Steven Souza) Cerro Armazones (Chile) (Bryce Babcock and Joseph Gangestad) Las Campanas (Chile) Cerro Pachón (Chile).
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Occultation by Charon 2005 C313.2 • Observed by 4 MIT–Williams teams on 5 telescopes: • Pico dos Dias (Brazil) – clouded out • (Jay Pasachoff and Steven Souza) • Cerro Armazones (Chile) • (Bryce Babcock and Joseph Gangestad) • Las Campanas (Chile) • Cerro Pachón (Chile) Movie of C313.2 from Las Campanas- http://occult.mit.edu/research/C313OccMovie.php
Cerro Armazones, Chile (L to R) M. J. Person, B. A. Babcock, & J. W. Gangestad Pico dos Dias, Brazil S. P. Souza (L), J. M. Pasachoff (R)
Where we were … … and the parts of Charon we saw
Cerro Armazones Light Curve Duration: 37 sec Mid-time: 03:36:36.5 UT Sharp drop No atmosphere detected
Team Light Curves Du Pont Telescope (2.5 m), Las Campanas Clay Telescope (6.5 m), Las Campanas 6.5-m 2.5-m 8-m 0.85-m Gemini South (8 m) Cerro Pachón Cerro Armazones (0;.84 m), Antofagasta, Chile
Upper Limits on Charon’s Atmosphere Seconds after reference time Clay Telescope data Gas Molecular Weight (amu) Number density (1013 cm-3) CH4 16.04 2.0 H2O 18.02 3.4 Ne 20.18 11.9 N2 28.01 2.3 Ar 39.95 2.0 Gulbis, A.A.S., Elliot, J.L., Person, M.J., Adams, E.R., Babcock, B.A., Emilio, M., Gangestad, J.W., Kern, S.D., Kramer, E.A., Osip, D.J., Pasachoff J.M., Souza, S.P., Tuvikene, T. “Charon’s radius and atmospheric constraints from stellar occultation observations” Nature, in press
Radius and Composition Constraints Radius: 606 ± 8 km Density: 1.72 ± 0.15 g/cm3 Rock/Ice: 0.63 ± 0.05 This rock/ice fraction is consistent with a collisional formation scenario. http://ncsdweb.ncsd.k12.wy.us/planetarium/ART/moonimpact.jpg