7 oct. : la poussière interstellaire
Cosmic dust: near and far
par Melanie Koehler (Institut d'astrophysique spatiale)
Jeudi 7 octobre 2010 à 14 h, bât. 121, salle 1-2-3
Dust particles can be found in all regions in space. Dust is known from observations in the solar system, for example the Zodiacal light and cometary tails. Dust can be detected in extra-solar systems and in the interstellar medium. The properties of dust particles, such as size distribution, material composition and shape, might change from locality to locality. Unusual silicate features are for example detected in spectra observing dust in active-galactic nuclei (AGN).
Observations of dust particles can be analysed with model calculations which give indication of dust properties. For these model calculations the absorption and scattering of dust grains have to be determined. For different dust properties, mainly the grain's shape, different light-scattering theories are available which have to be chosen carefully. The material composition of the dust grains is included in the calculations using the optical constants obtained from laboratory measurements. Regarding the size distribution, for very small particles (nanoparticles) a different approach has to be considered to determine the absorption coefficient.
I will present an introduction to cosmic dust focussing on the analysis of observations with model calculations. Results are shown for dust in extra-solar planetary systems and in the interstellar medium. I will further present laboratory spectral measurements of material separated from primitive meteorites.
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