Abstract/Details

LIGHTCURVE CCD SPECTROPHOTOMETRY OF PLUTO


1984 1984

Other formats: Order a copy

Abstract (summary)

An observational program was carried out to investigate the spectrum of Pluto at various points on its lightcurve. Spectrophotometry of Pluto in the wavelength range of 5600 to 10500 (ANGSTROM) was obtained on four nights covering lightcurve phases of 0.18, 0.35, 0.49, and 0.98. The four phases included minimum light (0.98) and one near maximum light (0.49). The spectra reveal variations in the adsorption depths of the methane bands at 6200, 7200, 7900, 8400, 8600, 8900, and 10000 (ANGSTROM). The minimum amount of adsorption was found to occur at minimum light.

A model for the surface and atmosphere of Pluto was constructed in an attempt to explain the phase variation observed. The model is based upon a previous photometric two-spot model which was constructed to explain the variations in the lightcurve from 1950 to 1982. Two dark circular spots (46(DEGREES) and 28(DEGREES) in radius, both at latitude -23(DEGREES), separated by 134(DEGREES) in longitude) were used to constrain the surface distribution of methane frost on the surface of Pluto. The reflectance properties of the two terrains were modelled with a theory by B. Hapke (J.G.R., v. 86, p. 3039, 1981) which includes the effects of multiple scattering in the surface frost. The particle size and continuum optical depth of the frost particles were allowed to vary between the dark regions inside the spot boundaries and the brighter regions surrounding the spots. The transmission of the atmosphere was calculated using the Mayer-Goody band model.

The model fit to the spectrum required the presence of a frost with particle sizes on the order of 1-20 mm in order to explain the observed phase dependence of the methane bands. Using only the atmosphere and no surface frost implies a variation in column abundance of 30% within three days. From energy balance considerations this variation in column abundance is not possible. By including the absorption of methane frost on the surface a range of model solutions was obtained. This range yields an approximate limit of 5.5 m-amagats to the amount of gas that can be present and still achieve a good fit to the phase variation of the 7200 (ANGSTROM) band. If the atmosphere is removed from the model an equally good fit to the 7200 (ANGSTROM) band is obtained.

A major problem with the model is its failure to reproduce the relative absorption band depths. The gaseous atmospheric calculation on the other hand can fit the spectrum quite well. Possible explanations include a particle size distribution within a given terrain.

Indexing (details)


Subject
Astronomy;
Astrophysics
Classification
0606: Astronomy
0606: Astrophysics
Identifier / keyword
Pure sciences
Title
LIGHTCURVE CCD SPECTROPHOTOMETRY OF PLUTO
Author
BUIE, MARC WILLIAM
Number of pages
116
Publication year
1984
Degree date
1984
School code
0009
Source
DAI-B 46/01, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
University/institution
The University of Arizona
University location
United States -- Arizona
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
8505225
ProQuest document ID
303345266
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/303345266/fulltextPDF
Access the complete full text

You can get the full text of this document if it is part of your institution's ProQuest subscription.

Try one of the following:

  • Connect to ProQuest through your library network and search for the document from there.
  • Request the document from your library.
  • Go to the ProQuest login page and enter a ProQuest or My Research username / password.