Light Scattering by Dust Particles in the Outer Solar System

Abstract

AbstractPhotometric observations of the zodiacal light performed by Pioneer 10 indicated that there may be very little scattering by dust in the outer solar system. To shed more light on this problem we formulate explicit expressions for interpreting the brightness observed by a spacecraft travelling inside or outside a finite homogeneous cloud of scattering particles. An application is made to the ecliptic zodiacal light brightness as observed by Pioneer 10 and tabulated by Toller and Weinberg (1985). A satisfactory interpretation of these data as well as earthbound observations can be given by means of a model having a particle density distribution or mean scattering cross section which vanishes beyond 2.8 - 3.7 AU. Some implications for the nature and spatial distribution of the interplanetary dust are discussed.