Portal de Periódicos da CAPES

Determination of the Charon/Pluto Mass Ratio from Center-of-Light Astrometry

1997; Elsevier BV; Volume: 126; Issue: 2 Linguagem: Inglês

10.1006/icar.1996.5656

1090-2643

Jeffrey A. Foust, J. L. Elliot, C. B. Olkin, S. W. McDonald, Edward W. Dunham, R. P. S. Stone, John S. McDonald, Ronald C. Stone,

Planetary Science and Exploration

The Charon/Pluto mass ratio is a fundamental but poorly known parameter of the two-body system. Previous values for the mass ratio have ranged from 0.0837 ± 0.0147 (Nullet al., 1993,Astron. J.105, 2319–2335) to 0.1566 ± 0.0035 (Younget al., 1994,Icarus108, 186–199). We report here a new determination of the Charon/Pluto mass ratio, using five sets of groundbased images taken at four sites in support of Pluto occultation predictions. Unlike the Nullet al.and Younget al.determinations, where the centers of light for Pluto and Charon could be determined separately, this technique examines the motion of the center of light of the blended Pluto–Charon image. We compute the offsets of the observed center-of-light position of Pluto–Charon from the ephemeris position of the system and fit these offsets to a model of the Pluto–Charon system. The least-squares fits to the five data sets agree within their errors, and the weighted mean mass ratio is 0.117 ± 0.006. The effects of errors in the Charon light fraction, semimajor axis, and ephemeris have been examined and are equal to only a small fraction of the formal error from the fit. This result is intermediate between those of Nullet al.and Younget al.and matches a new value of 0.124 ± 0.008 by Null and Owen (1996,Astron. J.111, 1368–1381). The mass ratio and resulting individual masses and densities of Pluto and Charon are consistent with a collisional origin for the Pluto–Charon system.