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Title: Pluto-charon mutual events

Abstract

Since 1985, planetary astronomers have been working to take advantage of a once-per-century apparent alignment between Pluto and its satellite, Charon, which has allowed mutual occultation and transit events to be observed. There events, which will cease in 1990, have permitted the first precise determinations of their individual radii, densities, and surface compositions. In addition, information on their surface albedo distributions can be obtained.

Authors:
 [1]
  1. (Massachusetts Institute of Technology, Cambridge (USA))
Publication Date:
OSTI Identifier:
5917073
Resource Type:
Journal Article
Resource Relation:
Journal Name: Geophysical Research Letters (American Geophysical Union); (USA); Journal Volume: 16:11
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; PLUTO PLANET; SATELLITES; ALBEDO; ALIGNMENT; CHEMICAL COMPOSITION; DENSITY; ECLIPSE; GEOMETRY; MONITORING; PHOTOMETRY; SIZE; SURFACES; MATHEMATICS; PHYSICAL PROPERTIES; PLANETS; 640107* - Astrophysics & Cosmology- Planetary Phenomena

Citation Formats

Binzel, R.P. Pluto-charon mutual events. United States: N. p., 1989. Web. doi:10.1029/GL016i011p01205.
Binzel, R.P. Pluto-charon mutual events. United States. doi:10.1029/GL016i011p01205.
Binzel, R.P. 1989. "Pluto-charon mutual events". United States. doi:10.1029/GL016i011p01205.
@article{osti_5917073,
title = {Pluto-charon mutual events},
author = {Binzel, R.P.},
abstractNote = {Since 1985, planetary astronomers have been working to take advantage of a once-per-century apparent alignment between Pluto and its satellite, Charon, which has allowed mutual occultation and transit events to be observed. There events, which will cease in 1990, have permitted the first precise determinations of their individual radii, densities, and surface compositions. In addition, information on their surface albedo distributions can be obtained.},
doi = {10.1029/GL016i011p01205},
journal = {Geophysical Research Letters (American Geophysical Union); (USA)},
number = ,
volume = 16:11,
place = {United States},
year = 1989,
month =
}
  • The present first order analytical and numerical models of light curves due to mutual events between close planetary binaries, the effects of shadowing are included. Attention is given to the case of the Pluto-Charon system. The results of the analytical and numerical approaches agree to well within the expected light curve measurement error. The model predicts that the current mutual eclipse event series will end by November 1990. 12 references.
  • As part of the planned 'Pluto-Charon Mutual Eclipse Season Campaign', one mutual event was observed at the ESO Observatory on July 10, 1986 and seven mutual events were observed at the Serra La Nave stellar station of Catania Astrophysical Observatory from April 29 to July 21, 1987. At ESO the measurements were performed at the 61-cm Bochum telescope equipped with a photon-counting system and U, B, V, filters; at Serra La Nave the Cassegrain focus of the 91-cm reflector was equipped with a photon-counting system and B and V filters. The observed light losses and contact times do not showmore » relevant systematic deviations from the predicted ones. An examination of the behavior of the B and V light curves gives slight indications of a different slope of the B and V light loss of the same event for a superior or an inferior event, and shows that the superior events are shallower at wavelengths longer than B. 6 refs.« less
  • This year is the last of a five-year interval when the Earth passes through the orbital plane of Pluto and its satellite Charon, causing alternate transits and occultations of the satellite as seen from Earth. Spectrophotometric observations of the system made both in and out of eclipse were obtained in the visual and near-infrared. The Pluto-Charon system is found to be compositionally diverse, a result unanticipated before the mutual events. Water frost was identified and is ubiquitous on Charon's surface, while Pluto has a methane veneer. The spectral activity of Pluto's methane is seen to vary with rotational phase. Onmore » Pluto, surface albedo appears to be correlated with composition. Dark regions tend to be redder and depleted in methane relative to bright regions. Dependence of geometric albedo with wavelength were calculated for both bodies, from 0.4 to 2.4 microns. The albedo model of Marcialis (1983, 1988) has emerged favorably after several severe tests. Accurate radii and system bulk density derived from the mutual events were used to construct models of phenomena unanticipated a decade ago. Recent interior models are used to show that viscous relaxation of topography is expected to be significant on Pluto but not on Charon. Horizontal topographic features on the primary probably are limited in extent to less than a few tens of kilometers. Globally, Pluto's figure is essentially hydrostatic. Astrometric observations of the system are presented, as evidence that the discovery of Charon just seven years before the initial mutual events was not fortuitous, but most probable. The astrometry will help to refine Pluto's orbit, making prediction of future stellar occultations by the system more reliable.« less
  • We present new imaging of the surface of Pluto and Charon obtained during 2002-2003 with the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) instrument. Using these data, we construct two-color albedo maps for the surfaces of both Pluto and Charon. Similar mapping techniques are used to re-process HST/Faint Object Camera (FOC) images taken in 1994. The FOC data provide information in the ultraviolet and blue wavelengths that show a marked trend of UV-bright material toward the sunlit pole. The ACS data are taken at two optical wavelengths and show widespread albedo and color variegation on the surface ofmore » Pluto and hint at a latitudinal albedo trend on Charon. The ACS data also provide evidence for a decreasing albedo for Pluto at blue (435 nm) wavelengths, while the green (555 nm) data are consistent with a static surface over the one-year period of data collection. We use the two maps to synthesize a true visual color map of Pluto's surface and investigate trends in color. The mid- to high-latitude region on the sunlit pole is, on average, more neutral in color and generally higher albedo than the rest of the surface. Brighter surfaces also tend to be more neutral in color and show minimal color variations. The darker regions show considerable color diversity arguing that there must be a range of compositional units in the dark regions. Color variations are weak when sorted by longitude. These data are also used to constrain astrometric corrections that enable more accurate orbit fitting, both for the heliocentric orbit of the barycenter and the orbit of Pluto and Charon about their barycenter.« less
  • Various methods for estimating the diameters of Pluto and Charon are discussed. The application of speckle interferometry, the timing of occultations, and the monitoring of Charon and Pluto rotations to calculate the diameter of the planet and its satellite are described. Walker (1980) estimated Charon's diameter as greater than 1200 km using the occultated star method; the speckle interferometry estimates of Baier and Weigelt (1983) are between 2710-3460 km for Pluto and between 1050-1520 km for Charon; and using the mutual events method Dunbar and Tedesco (1986) estimated the diameter of Pluto as 2300 + or - 100 km andmore » of Charon as 1500 + or - 100 km. The use of IRAS data combined with visual brightness to estimate planet and satellite diameters is examined; Tedesco et al. (1987) estimated Pluto's diameter as 2200 + or - 150 km and Charon's as 1300 + or - 150 km, and Aumann and Walker (1987) obtained estimates of 2360 km for Pluto and 1534 km for Charon. The compositions of Pluto's and Charon's atmospheres are analyzed.« less