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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.

5751 Zao
Discovered byM. Koishikawa
Discovery siteAyashi Station
Discovery date5 January 1992
MPC designation(1992) AC
Named after
Mount Zaō
MPO 319156, 1989 EN1
Amor Amor
Orbital characteristics[2]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 0
Observation arc9792 days (26.81 yr)
Aphelion2.994076221 AU (447.9074274 Gm)
Perihelion1.21174819 AU (181.274949 Gm)
2.102912204 AU (314.5911880 Gm)
3.05 yr (1113.9 d)
0° 19m 23.523s / day
Earth MOID0.244159 AU (36.5257 Gm)
Physical characteristics
Dimensions2.3 km[3]
Mean radius
1.15 km
76 h (3.2 d)[3]

Physical propertiesEdit

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.[4] Another group led by Wisniewski conducted an approximately 5 hour observation and were unable to conclude a rotational period.[5] 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.[6] Using the asteroid's albedo and the Near Earth Asteroid Thermal Model (NEATM) the asteroid's diameter 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]


  1. ^ "(5751) Zao = 1992 AC = 1989 EN1". Minor Planet Center. Retrieved 2015-06-04.
  2. ^ "5751 Zao (1992 AC)". JPL Small-Body Database. NASA/Jet Propulsion Laboratory. Retrieved 13 April 2016.
  3. ^ a b c d "5751 Zao". European Asteroid Research Node. Archived from the original on 2013-09-03. Retrieved 2008-03-30.
  4. ^ Pravec, P.; et al. (December 1997). "The Near-Earth Objects Follow-Up Program". Icarus. 130 (2): 275–286. Bibcode:1997Icar..130..275P. doi:10.1006/icar.1997.5816.
  5. ^ Wisniewski, W. Z.; MichaŁowski, T. M.; Harris, A. W.; McMillan, R. S. (April 1997). "Photometric Observations of 125 Asteroids". Icarus. 126 (2): 395–449. Bibcode:1997Icar..126..395W. doi:10.1006/icar.1996.5665.
  6. ^ a b Delbó, Marco; Harris, Alan W.; Binzel, Richard P.; Pravec, Petr; Davies, John K. (November 2003). "Keck observations of near-Earth asteroids in the thermal infrared". Icarus. 166 (1): 116–130. Bibcode:2003Icar..166..116D. doi:10.1016/j.icarus.2003.07.002.
  7. ^ "Ondrejov Asteroid Photometry Project: Summary of Prepublished Data".

External linksEdit