Physics
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.p13c0183e&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #P13C-0183
Physics
6008 Composition (1060), 6020 Ices, 6205 Asteroids, 6210 Comets (6023), 6224 Kuiper Belt Objects
Scientific paper
From the standpoint of their composition, Kuiper Belt Objects (KBOs) are still a puzzle: some of them contain water ice, some methane and ethan ice, some are rich in pyroxenes and/or olivine, and some contain a reddening agent that, we think, has to be organic in nature. Overall it is still a puzzle whose pieces are slowly coming together with the improvements in telescopes and instrumentation, including space-based observatories and spacecraft. We have measured reflectances of 12 KBOs, 8 Centaurs, and 10 low albedo Trojan asteroids with the infrared array camera (IRAC) on the Spitzer Space Telescope. IRAC measures broadband fluxes at 3.6, 4.5, 5.8, and 8.0 μm. Reflectance is measured for all 30 objects at 3.6 and 4.5 μm. Only a handful of TNOs and Centaurs are bright enough for the detection of reflected flux at 5.8 μm, none are detected at 8.0 μm. For the low albedo Trojan asteroids, the flux at 5.8 μm is a combination of reflection and emission, whereas the 8.0 μm flux is dominated by thermal emission. Ground-based spectra have previously been published from the visible to 2.5 μm for all objects in the target list. In some cases, particularly for the featureless spectra, spectral models admit a range of possible compositions. Reflectances in the IRAC bands allow discrimination between these possible spectral models, thereby constraining surface compositions. For objects whose vis-NIR spectra show specific absorption bands (e.g., H2O), the IRAC data permit refinement of the spectral interpretations. For example, the IRAC data of 50000 Quaoar show evidence for H2O absorption, as expected from the bands detected at 1.5 and 2.0 μm previously, though slight refinement of the surface model is necessary to properly fit the new data points. We will present these new data and implications for the compositions of the individual objects thus far observed.
Cruikshank Dale P.
Dalle Ore Cristina
Emery Joshua P.
Fernandez Yan R.
Stansberry John Arthur
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