| Discovery[1] | |
|---|---|
| Discovered by | M. Koishikawa |
| Discovery site | Ayashi Station |
| Discovery date | 5 January 1992 |
| Designations | |
| (1992) AC | |
Named after | Mount Zaō |
| MPO 319156, 1989 EN1 | |
Amor NEO | |
| Orbital characteristics[2] | |
| Epoch 13 January 2016 (JD 2457400.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 9792 days (26.81 yr) |
| Aphelion | 2.994076221 AU (447.9074274 Gm) |
| Perihelion | 1.21174819 AU (181.274949 Gm) |
| 2.102912204 AU (314.5911880 Gm) | |
| Eccentricity | 0.423776140 |
| 3.05yr (1113.9d) | |
| 300.120144° | |
| 0° 19m 23.523s / day | |
| Inclination | 16.0739405° |
| 121.691193° | |
| 25.2587992° | |
| Earth MOID | 0.244159 AU (36.5257 Gm) |
| Physical characteristics | |
| 2.3 km[3] | |
| 76 h (3.2 d)[3] | |
| 0.36[3] | |
| 14.8 | |
5751 Zao,provisional designation1992 AC, is anAmor asteroid discovered by Japanese astronomerM. Koishikawa at theAyashi Station of theSendai Astronomical Observatory on 5 January 1992
Zao has been observed by several groups to determine its rotational period. Itslight curve was observed byPravec, 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.[4] Another group led by Wisniewski conducted an approximately 5 hour observation and were unable to conclude a rotational period.[5]Zao was again observed in 2001 byDelbó, et al. using theKeck telescope. They were able to determine the asteroid'salbedo of 0.36 and re-classify the asteroid fromX-type toE-type.[6] Using the asteroid's albedo and theNear Earth Asteroid Thermal Model (NEATM) the asteroid'sdiameter was estimated to be 2.3 km.[6] Further study of the asteroid by the Ondrejov Asteroid Photometry Project concludes that a rotational period of 76 hours is consistent with earlier measurements.[3][7]
