Radiometric diameter and albedo of the remarkable asteroid 1976AA

THE minor planet 1976 A A (Fast-Moving Object Helin), discovered on January 7, 1976, is the first asteroid found with an orbital period of < 1 yr (orbital elements a=0.97, e=0.18; i=19°; ref. 1). Although it seems to be a likely speculation that 1976 AA is a former Apollo object that originally had its aphelion in the main asteroid belt, it is possible that this object is a member of a group of minor planets that is distinct in physical as well as orbital properties. Observations that reveal the physical nature (colour, albedo, texture, mineralogy) of its surface are needed to compare it with better studied objects in more orthodox orbits. This letter reports a determination by infrared radiometry of the diameter and albedo of 1977AA.