Observations of the Near-Infrared Spectrum of the Zodiacal Light with CIBER

TL;DR

This study uses CIBER to analyze the near-infrared spectrum of zodiacal light, revealing silicate features and suggesting S-type asteroid dust as a significant component of interplanetary dust.

Contribution

First spectral detection of a broad absorption feature at 900 nm in zodiacal light, indicating silicates, and analysis of dust sources based on spectral shape and isotropy.

Findings

Zodiacal light spectrum is redder than the solar spectrum.

A broad absorption feature at approximately 900 nm suggests silicates.

Spectral shape consistent with S-type asteroid dust, indicating its dominance in interplanetary dust.

Abstract

Interplanetary dust (IPD) scatters solar radiation which results in the zodiacal light that dominates the celestial diffuse brightness at optical and near-infrared wavelengths. Both asteroid collisions and cometary ejections produce the IPD, but the relative contribution from these two sources is still unknown. The Low Resolution Spectrometer (LRS) onboard the Cosmic Infrared Background Experiment (CIBER) observed the astrophysical sky spectrum between 750 and 2100 nm over a wide range of ecliptic latitude. The resulting zodiacal light spectrum is redder than the solar spectrum, and shows a broad absorption feature, previously unreported, at approximately 900 nm, suggesting the existence of silicates in the IPD material. The spectral shape of the zodiacal light is isotropic at all ecliptic latitudes within the measurement error. The zodiacal light spectrum, including the extended wavelength range to 2500 nm using IRTS data, is qualitatively similar to the reflectance of S-type asteroids. This result can be explained by the proximity of S-type asteroidal dust to Earth's orbit, and the relativily high albedo of asteridal dust compared with cometary dust.