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Keck observations of near-Earth asteroids in the thermal infrared |
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| Authors: | Marco Delbó Alan W Harris Richard P Binzel John K Davies |
| Institution: | a DLR Institute of Planetary Research, Rutherfordstrasse 2, 12489 Berlin, Germany b Department of Earth, Atmospheric, and Planetary Sciences, MIT, Cambridge, MA 02139, USA c Astronomical Institute, Academy of Sciences of the Czech Republic, CZ-25165 Ond?ejov, Czech Republic d Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK |
| Abstract: | We present the results of thermal-infrared observations of 20 near-Earth asteroids (NEAs) obtained in the period March 2000-February 2002 with the 10-m Keck-I telescope on Mauna Kea, Hawaii. The measured fluxes have been fitted with thermal-model emission continua to determine sizes and albedos. This work increases the number of NEAs having measured albedos by 35%. The spread of albedos derived is very large (pv=0.02−0.55); the mean value is 0.25, which is much higher than that of observed main-belt asteroids. In most cases the albedos are in the ranges expected for the spectral types, although some exceptions are evident. Our results are consistent with a trend of increasing albedo with decreasing size for S-type asteroids with diameters below 20 km. A number of objects are found to have unexpectedly low apparent color temperatures, which may reflect unusual thermal properties. However, the results from our limited sample suggest that high thermal-inertia, regolith-free objects may be uncommon, even amongst NEAs with diameters of less than 1 km. We discuss the significance of our results in the light of information on these NEAs taken from the literature and the uncertainties inherent in applying thermal models to near-Earth asteroids. |
| Keywords: | Asteroids Infrared observations Photometry Spectrophotometry |
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