Anomalous extinction in the orion nebula: Analysis in a first approximation

Analysis of reddening data (λ-1 ≤ 8 μm-1) for nine hot stars situated in the central, brightest part of the Orion nebula reveals that the observed extinction is a mixture of a normal component and an anomalous component that differs from star to star. The anomalous component, in its turn, consists of continuum extinction by large (visual) grains and absorption in the hump at λ0 = 0.22 μm. The absorption in the hump varies strongly from star to star and on the average is seven times weaker than the normal interstellar extinction. It is shown that the radii of the grains are distributed in accordance with an exponential law f(a) = exp(-a/a0). According to an estimate, the refractive index m is closer to 1.3 than to 1.6. The mean grain radius is a0 = 0.12 μm if m = 1.3. 34 refs., 3 figs., 1 tab