Initial Result of Heliocentric Distance Dependence of Zodiacal Light Observed by Hayabusa2#

Abstract

The zodiacal light (ZL) is sunlight scattered by interplanetary dust (IPD) in the optical wavelengths. The spatial distribution of IPD in the Solar system may hold an important key to understanding the evolution of the Solar system and material transportation within it. The IPD number density can be expressed as [[EQUATION]] , and the result of [[EQUATION]] was obtained by the previous observations from the interplanetary space by Helios 1/2 and Pioneer 10/11 in the 1970s and 1980s. However, no direct measurements of [[EQUATION]] based on the ZL observation from the interplanetary space outside the Earth's orbit have been conducted since then. Here we introduce the initial result of the ZL radial profile at optical wavelengths observed at 0.76-1.06 au by ONC-T with Hayabusa2# mission in 2021-2022. The obtained ZL brightness is well reproduced by the model brightness, but there is a small excess of the observed ZL brightness over the model brightness at around 0.9 au. The obtained radial power-law index is [[EQUATION]] , which is consistent with the previous results based on the ZL observations. The dominant uncertainty source arises from the uncertainty in the Diffuse Galactic Light estimation.