Visible to Thermal-Infrared Spectrophotometry of a Possible Inactive Cometary Nucleus

Kurzfassung

LD31 is one of the few objects with retrograde orbits listed in the Minor Planet Catalog and thsu designated as asteroids rather than comets. Observations of (20461) 1999 LD31 made in March 2000 with the 10-m Keck I telescope indicate an optical albedo, pv, of 0.03+-0.01 and diameter of 14 +- 3 km. The low albedo and the results of spectrophotometry carried out with the University of Hawaii 2.2-m and the UK 3.8-m infrared telescopes are indicative of a D-type asteroid or cometary nucleus. These results, together with the nature of an orbit originating in the outer Solar System that has evolved into an orbit characteristic of a Halley-type comet and may be the nucleus of an extinct or dormant comet.