The Thousand Asteroid Light Curve Survey

TL;DR

This survey of over 800 Main Belt asteroids using the Canada-France-Hawaii Telescope analyzed their rotation periods and shapes, revealing an excess of slow rotators, large amplitude shapes, and a few potentially fast-spinning objects near the break-up limit.

Contribution

First large-scale, debiased survey of asteroid rotation periods and shapes, providing new insights into their distribution and physical properties.

Findings

Confirmed excess of slow rotators among Main Belt asteroids.

Identified a subset with large light curve amplitudes (~1 mag).

Discovered a small population of potential ultra-fast rotators below 2 hours.

Abstract

We present the results of our Thousand Asteroid Light Curve Survey (TALCS) conducted with the Canada-France-Hawaii Telescope in September 2006. Our untargeted survey detected 828 Main Belt asteroids to a limiting magnitude of g'~22.5 corresponding to a diameter range of 0.4 km <= D <= 10 km. Of these, 278 objects had photometry of sufficient quality to perform rotation period fits. We debiased the observations and light curve fitting process to determine the true distribution of rotation periods and light curve amplitudes of Main Belt asteroids. We confirm a previously reported excess in the fraction of fast rotators but find a much larger excess of slow rotating asteroids (~15% of our sample). A few percent of objects in the TALCS size range have large light curve amplitudes of ~1 mag. Fits to the debiased distribution of light curve amplitudes indicate that the distribution of triaxial ellipsoid asteroid shapes is proportional to the square of the axis-ratio, (b/a)^2, and may be bi-modal. Finally, we find six objects with rotation periods that may be less than 2 hours with diameters between 400 m and 1.5 km, well above the break-up limit for a gravitationally-bound aggregate. Our debiased data indicate that this population represents <4% of the Main Belt in the 1-10 km size range.