1922 Zulu

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1922 Zulu
Discovery [1]
Discovered byE. Johnson
Discovery siteJohannesburg Obs.
Discovery date25 April 1949
MPC designation(1922) Zulu
Named after
Zulu (tribe)[2]
1949 HC
main-belt · (outer)[1][3]
2:1 res [4]
Orbital characteristics[1]
Epoch 16 February 2017 (JD 2457800.5)
Uncertainty parameter 0
Observation arc67.70 yr (24,727 days)
Aphelion4.7945 AU
Perihelion1.6775 AU
3.2360 AU
5.82 yr (2,126 days)
0° 10m 9.48s / day
Earth MOID0.7153 AU
Jupiter MOID0.6296 AU
Physical characteristics
Dimensions12.41±2.60 km[5]
19.30 km (calculated)[3]
20.561±0.321 km[6][7]
18.64±0.01 h[8]
18.65 h[9]
0.057 (assumed)[3]
12.2[6] · 12.27±0.24[10] · 12.3[1][3][5]

1922 Zulu, provisional designation 1949 HC, is a carbonaceous asteroid in a strongly unstable resonance with Jupiter, located in the outermost regions of the asteroid belt, and approximately 20 kilometers in diameter. It was discovered on 25 April 1949, by South African astronomer Ernest Johnson at Union Observatory in Johannesburg, and named for the South African Zulu people.[2][11]

Orbit and classification[edit]

Zulu is one of few strongly unstable asteroids located near the 2:1 orbital resonance with the gas giant Jupiter, that corresponds to one of the prominent Kirkwood gaps in the asteroid belt.[4]

It orbits the Sun at a distance of 1.7–4.8 AU once every 5 years and 10 months (2,126 days). Its orbit has an eccentricity of 0.48 and an inclination of 35° with respect to the ecliptic.[1] The body's observation arc begins with its official discovery observation at Johannesburg, as no precoveries were taken and no prior identifications were made.[11]

Zulu was lost shortly after its 1949-discovery (see Lost asteroid), and only rediscovered in 1974 by Richard Eugene McCrosky, Cheng-yuan Shao and JH Bulger based on a predicted position by C. M. Bardwell of the Cincinnati Observatory.[12] It is quite highly inclined for asteroids in the asteroid belt, with an inclination of 35.4 degrees. This may be related to its 2:1 resonance with Jupiter.

Physical characteristics[edit]

In May 2002, a rotational lightcurve of Zulu was obtained from photometric observations by American astronomer Robert Stephens at the Santana Observatory in California. Lightcurve analysis gave a well-defined rotation period of 18.64 hours with a brightness variation of 0.11 magnitude (U=3).[8] One month later, French amateur astronomers René Roy and Laurent Brunetto obtained another lightcurve with a concurring period of 18.65 hours and an amplitude of 0.09 magnitude (U=1).[9]

According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Zulu measures 12.41 and 20.561 kilometers in diameter and its surface has an albedo of 0.055 and 0.16.[5][6][7] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous C-type asteroid of 0.057 and calculates a diameter of 19.30 kilometers with an absolute magnitude of 12.3.[3]


This minor planet was named after the South African Zulu people, in recognition of the tribesmen who devotedly worked at the Johannesburg Union Observatory. The name also closely relates to 1362 Griqua and 1921 Pala, which also received tribal names and librate in the 2:1 ratio of Jupiter's mean motion as well.[2] The naming citation was published before November 1977 (M.P.C. 3938).[13]

See also[edit]


  1. ^ a b c d e "JPL Small-Body Database Browser: 1922 Zulu (1949 HC)" (2017-01-05 last obs.). Jet Propulsion Laboratory. Retrieved 31 March 2017.
  2. ^ a b c Schmadel, Lutz D. (2007). "(1922) Zulu". Dictionary of Minor Planet Names – (1922) Zulu. Springer Berlin Heidelberg. p. 154. doi:10.1007/978-3-540-29925-7_1923. ISBN 978-3-540-00238-3.
  3. ^ a b c d e f "LCDB Data for (1922) Zulu". Asteroid Lightcurve Database (LCDB). Retrieved 31 March 2017.
  4. ^ a b Roig, F.; Nesvorný, D.; Ferraz-Mello, S. (September 2002). "Asteroids in the 2 : 1 resonance with Jupiter: dynamics and size distribution [ Erratum: 2002MNRAS.336.1391R ]". Monthly Notices of the Royal Astronomical Society. 335 (2): 417–431. Bibcode:2002MNRAS.335..417R. doi:10.1046/j.1365-8711.2002.05635.x. Retrieved 31 March 2017.
  5. ^ a b c d Nugent, C. R.; Mainzer, A.; Masiero, J.; Bauer, J.; Cutri, R. M.; Grav, T.; et al. (December 2015). "NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos". The Astrophysical Journal. 814 (2): 13. arXiv:1509.02522. Bibcode:2015ApJ...814..117N. doi:10.1088/0004-637X/814/2/117. Retrieved 31 March 2017.
  6. ^ a b c d Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90.
  7. ^ a b c Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Dailey, J.; et al. (November 2011). "Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters". The Astrophysical Journal. 741 (2): 20. arXiv:1109.4096. Bibcode:2011ApJ...741...68M. doi:10.1088/0004-637X/741/2/68. Retrieved 31 March 2017.
  8. ^ a b Stephens, R. D. (December 2002). "Photometry of 769 Tatjana, 818 Kapteyna, 1922 Zulu, and 3687 Dzus". The Minor Planet Bulletin. 29: 72. Bibcode:2002MPBu...29...72S. Retrieved 31 March 2017.
  9. ^ a b Behrend, Raoul. "Asteroids and comets rotation curves – (1922) Zulu". Geneva Observatory. Retrieved 31 March 2017.
  10. ^ Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results". Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 31 March 2017.
  11. ^ a b "1922 Zulu (1949 HC)". Minor Planet Center. Retrieved 31 March 2017.
  12. ^ Brian G. Marsden (24 October 1974). "International Astronomical Union Circular 2710 – 1949 HC (3rd item)". Central Bureau for Astronomical Telegrams. Retrieved 31 March 2017.
  13. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 31 March 2017.

External links[edit]