Main Belt Asteroids with WISE/NEOWISE I: Preliminary Albedos and Diameters

TL;DR

This study uses WISE/NEOWISE infrared data to measure diameters and albedos of over 100,000 Main Belt asteroids, revealing regional and family-related albedo patterns, with initial results subject to survey biases.

Contribution

First to analyze Main Belt asteroids using WISE/NEOWISE data, providing preliminary size and albedo distributions and identifying regional and familial albedo trends.

Findings

Albedo varies across the inner, middle, and outer Main Belt.

Albedo distributions are strongly bimodal within regions.

Asteroid families show characteristic albedos, with some exceptions.

Abstract

We present initial results from the Wide-field Infrared Survey Explorer (WISE), a four-band all-sky thermal infrared survey that produces data well suited to measuring the physical properties of asteroids, and the NEOWISE enhancement to the WISE mission allowing for detailed study of Solar system objects. Using a NEATM thermal model fitting routine we compute diameters for over 100,000 Main Belt asteroids from their IR thermal flux, with errors better than 10%. We then incorporate literature values of visible measurements (in the form of the H absolute magnitude) to determine albedos. Using these data we investigate the albedo and diameter distributions of the Main Belt. As observed previously, we find a change in the average albedo when comparing the inner, middle, and outer portions of the Main Belt. We also confirm that the albedo distribution of each region is strongly bimodal. We observe groupings of objects with similar albedos in regions of the Main Belt associated with dynamical breakup families. Asteroid families typically show a characteristic albedo for all members, but there are notable exceptions to this. This paper is the first look at the Main Belt asteroids in the WISE data, and only represents the preliminary, observed raw size and albedo distributions for the populations considered. These distributions are subject to survey biases inherent to the NEOWISE dataset and cannot yet be interpreted as describing the true populations; the debiased size and albedo distributions will be the subject of the next paper in this series.