#ASTEROIDS EXTREME SIZE CODE#
The quality code is assigned according to the reliability of the period result obtained. In this plot, we use only objects that have been assigned a quality code U ≥ 2−. This cutoff for "high amplitude" is largely arbitrary as to date there has been no work calculating a limit for rubble-pile asteroids accounting for angle of friction.įigure 1 shows the rotation rate of all main belt asteroids plotted against diameter as recorded in the Light Curve Database (LCDB Warner et al. In this research, we define an "extreme asteroid" as an object rotating with a period shorter than the spin barrier ( P < 2.2 hr), or an object with measured light curve amplitude A ≥ 1.0 mag. We classify "extreme" asteroids based on their shape and spin state data. In the course of this project, to date no large superfast rotators ( P rot < 2.2 hr) have been identified. An additional object not initially measured with A obs > 1.0 mag, 49257, was determined to have a shape model that does suggest a high-amplitude object.
Three asteroids were sufficiently observed to allow for shape and spin-pole models to be determined through light curve inversion. We find that none of the "high-amplitude asteroids" identified here require any unusual cohesive strengths to resist rotational fission. Three further objects, although below the cutoff for "high amplitude," had a combination of elongation and rotation period which also may require internal cohesive strength, depending on the density of the body. We find that these high-amplitude objects are most simply explained by single rubble-pile objects with some density-dependent internal strength, allowing them to resist mass shedding even at their highly elongated shapes. Four of the observed objects were found to have observed amplitude A obs ≥ 1.0 mag. Using the first 18 months of the Pan-STARRS 1 survey, we have identified 33 candidate high-amplitude objects for follow-up observations and carried out observations of 22 asteroids.