Discovered by M. Koishikawa MPC designation 1992 AC Minor planet category Amor
NEO Discovered 5 January 1992 Discoverer Masahiro Koishikawa Asteroid group Amor asteroid | Discovery date 5 January 1992 Alternative names MPO 319156, 1989 EN1 Observation arc 9792 days (26.81 yr) Orbits Sun Named after Mount Zaō | |
Discovery site Sendai Astronomical Observatory, Sendai Astronomical Observatory Ayashi Station Similar 1980 Tezcatlipoca, 4954 Eric, 1627 Ivar | ||
5751 Zao also designated 1992 AC is an Amor asteroid discovered on January 5, 1992 by M. Koishikawa at the Ayashi Station of the Sendai Astronomical Observatory.
Physical properties
5751 Zao has been observed by several groups to determine its rotational period. Its light curve was observed by Pravec, et al. between 1992 and 1995 with the intention of determining its rotational period. From its nearly constant brightness it was determined that the asteroid is roughly spherical and has a rotational period of ≥ 21.7 hr. Another group led by Wisniewski conducted an approximately 5 hour observation and were unable to conclude a rotational period. 5751 Zao was again observed in 2001 by Delbó, et al. using the Keck telescope. They were able to determine the asteroid's albedo of 0.36 and re-classify the asteroid from X-type to E-type. Using the asteroid's albedo and the Near Earth Asteroid Thermal Model (NEATM) the asteroid's diameter was estimated to be 2.3 km. Further study of the asteroid by the Ondrejov Asteroid Photometry Project concludes that a rotational period of 76 hours is consistent with earlier measurements.