Infrared Diameter of Vesta

Abstract

REMARKABLY few determinations have been made of the diameters and albedos of the minor planets. The figures usually quoted¹ were obtained seventy years ago by Barnard² using a filar micrometer on the 36-inch Lick and 40-inch Yerkes refractors. He was measuring disks a few tenths of a second of arc across, not much larger than the theoretical resolving power of these instruments, yet quoted on one occasion an estimated accuracy of ± 6 per cent. It is on the basis of these measurements that the albedos and diameters of all smaller asteroids have been estimated. Clearly better observations are needed. Kuiper measured a dozen minor planets in the 1950s using the 82-inch McDonald reflector but has not published the results.