Mid-Infrared spectrum of the zodiacal light

Reach W.T., Abergel A., Boulanger F., Desert F.-X., Perault M., Bernard J.-P., Blommaert J., Cesarsky C., Cesarsky D., Metcalfe L., Puget J.-L., Sibille F., Vigroux L.

Abstract:

Using the mid-infrared camera on the Infrared Space Observatory (ISO), the spectrum of a relatively empty piece of sky, dominated by zodiacal light, was measured from 5 to 16.5 m wavelength. The spectrum has no spectral features brighter than 15% of a blackbody fit to entire spectrum; the temperature of the fit is 261.5+/-1.5K. No galactic or cosmic background spectral features are detected. Comparison to models for three size distributions of spherical grains composed of several different materials reveals acceptable fits only for `astronomical silicate,' ruling out graphite, magnetite, andesite, obsidian, glassy carbon, or water ice as the constituent of material producing the zodiacal emission. The size distribution is constrained to have relatively fewer small particles compared to the coma of P/Halley. There is a hint of a 9-11 m feature, which suggests that the particles producing the zodiacal light are composed of silicates similar to those found in the coma of P/Halley, collected interplanetary dust particles, and the dust around the nearby star {beta} Pic.

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