1. Astronomical Photometry at Wavelengths of 8.5,10.5 and 11.6 µm. 2. Infrared Emission from Asteroids at Wavelengths of 8·5, 10.5 and 11.6 µm

Citation

Matson, Dennis Ludwig (1972) 1. Astronomical Photometry at Wavelengths of 8.5,10.5 and 11.6 µm. 2. Infrared Emission from Asteroids at Wavelengths of 8·5, 10.5 and 11.6 µm. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Y25B-JY16. https://resolver.caltech.edu/CaltechTHESIS:09132013-115339548

Abstract

The purpose of this thesis is to present new observations of thermal-infrared radiation from asteroids. Stellar photometry was performed to provide standards for comparison with the asteroid data. The details of the photometry and the data reduction are discussed in Part 1. A system of standard stars is derived for wavelengths of 8.5, 10.5 and 11.6 µm and a new calibration is adopted. Sources of error are evaluated and comparisons are made with the data of other observers.

The observations and analysis of the thermal-emission observations of asteroids are presented in Part 2. Thermal-emission lightcurve and phase effect data are considered. Special color diagrams are introduced to display the observational data. These diagrams are free of any model-dependent assumptions and show that asteroids differ in their surface properties.

On the basis of photometric models, (4) Vesta is thought to have a bolometric Bond albedo of about 0.1, an emissivity greater than 0.7 and a true radius that is close to the model value of 300^(+50)_(-30)km. Model albedos and model radii are given for asteroids 1, 2, 4, 5, 6, 7, 15, 19, 20, 27, 39, 44, 68, 80, 324 and 674. The asteroid (324) Bamberga is extremely dark with a model (~bolometric Bond) albedo in the 0.01 - 0.02 range, which is thought to be the lowest albedo yet measured for any solar-system body. The crucial question about such low-albedo asteroids is their number and the distribution of their orbits.

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