Spectral and Spin Measurement of Two Small and Fast-Rotating Near-Earth Asteroids

TL;DR

This study characterizes two small, fast-rotating near-Earth asteroids using spectral and imaging data, revealing their taxonomic types, physical properties, and rapid rotation rates, which are among the fastest known for such small objects.

Contribution

It provides detailed spectral, rotational, and physical measurements of two small near-Earth asteroids, including their taxonomic classification and rotation periods, expanding knowledge of small asteroid properties.

Findings

2012 KP24 is a C-complex asteroid with a 2.5-minute rotation period.

2012 KT42 is a B-type asteroid with a 3.63-minute rotation period.

Both asteroids are among the smallest and fastest-spinning near-Earth objects measured.

Abstract

In May 2012 two asteroids made near-miss "grazing" passes at distances of a few Earth-radii: 2012 KP24 passed at nine Earth-radii and 2012 KT42 at only three Earth-radii. The latter passed inside the orbital distance of geosynchronous satellites. From spectral and imaging measurements using NASA's 3-m Infrared Telescope Facility (IRTF), we deduce taxonomic, rotational, and physical properties. Their spectral characteristics are somewhat atypical among near-Earth asteroids: C-complex for 2012 KP24 and B-type for 2012 KT42, from which we interpret the albedos of both asteroids to be between 0.10 and 0.15 and effective diameters of 20+-2 and 6+-1 meters, respectively. Among B-type asteroids, the spectrum of 2012 KT42 is most similar to 3200 Phaethon and 4015 Wilson-Harrington. Not only are these among the smallest asteroids spectrally measured, we also find they are among the fastest-spinning: 2012 KP24 completes a rotation in 2.5008+-0.0006 minutes and 2012 KT42 rotates in 3.634+-0.001 minutes.