21873 Jindřichůvhradec

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21873 Jindřichůvhradec
Discovery [1]
Discovered byJ. Tichá
M. Tichý
Discovery siteKleť Obs.
Discovery date29 October 1999
MPC designation(21873) Jindřichůvhradec
Named after
Jindřichův Hradec[2]
(Czech town)
1999 UU3 · 1982 SN8
1988 XA5
main-belt · (outer)[3]
Orbital characteristics[5]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc34.52 yr (12,608 days)
Aphelion3.8041 AU
Perihelion2.4999 AU
3.1520 AU
5.60 yr (2,044 days)
0° 10m 33.96s / day
Physical characteristics
Dimensions7.183±0.136 km[6][7]
10.44 km (calculated)[3]
50.5874±0.0664 h[8]
0.057 (assumed)[3]
C (assumed)[3] · X[9]
12.9[6] · 12.90±0.17[9] · 13.1[5] · 13.184±0.005 (R)[8] · 13.63[3]

21873 Jindřichůvhradec, provisional designation 1999 UU3, is a dark Hygiean asteroid and relatively slower-than average rotator from the outer region of the asteroid belt, approximately 8 kilometers (5.0 miles) in diameter.

It was discovered by Czech astronomers Jana Tichá and Miloš Tichý at the South Bohemian Kleť Observatory on 29 October 1999, and named for the Czech town of Jindřichův Hradec.[1] It is arguably one of the most unpronounceable minor-planet names for non-Czech speakers.


The asteroid is a member of the Hygiea family (601),[4] a very large family of carbonaceous outer-belt asteroids, named after the fourth-largest asteroid, 10 Hygiea.[10] It orbits the Sun in the outer main-belt at a distance of 2.5–3.8 AU once every 5 years and 7 months (2,044 days). Its orbit has an eccentricity of 0.21 and an inclination of 4° with respect to the ecliptic.[5] The first precovery was obtained at Crimea–Nauchnij in 1982, extending the asteroid's observation arc by 17 years prior to its discovery.[1]

Physical characteristics[edit]

According to the survey carried out by the NEOWISE mission of NASA's space-based Wide-field Infrared Survey Explorer, the asteroid measures 7.2 kilometers in diameter and its surface has an albedo of 0.23.[6] Based on an absolute magnitude of 13.63, the Collaborative Asteroid Lightcurve Link calculates a diameter of 10.4 kilometers, assuming a standard albedo for carbonaceous C-type asteroids of 0.057,[3] which is in-line with the Hygiea family's overall spectral type.[10]:23 A large-scale survey by Pan-STARRS, however, classifies the body as a X-type asteroid, which metallic core group has an intermediate albedo between stony and carbonaceous bodies.[9]

In September 2010, a photometric lightcurve analysis at the U.S. Palomar Transient Factory, California, gave a long rotation period of 50.5874±0.0664 hours with a brightness variation of 0.61 in magnitude (U=2).[8] This makes it a relatively slow rotator for an asteroid of its size, which normally have periods of just a few hours rather than several days.


This minor planet was named after Jindřichův Hradec, a south Bohemian town in the Czech Republic. Founded in the 13th century, it is known for its Renaissance château and Gothic church, which is exactly built on the 15th meridian east of Greenwich. A line marks the course of the meridian in its paving stones.[2] For non-speakers of Czech, Jindřichůvhradec is arguably one of the most unpronounceable names among more than 20,00 named minor planets. The approved naming citation was published by the Minor Planet Center on 28 January 2002 (M.P.C. 44595).[11]


  1. ^ a b c "21873 Jindrichuvhradec (1999 UU3)". Minor Planet Center. Retrieved 3 April 2016.
  2. ^ a b Schmadel, Lutz D. (2007). "(21873) Jindřichůvhradec". Dictionary of Minor Planet Names – (21873) Jindřichůvhradec. Springer Berlin Heidelberg. p. 868. doi:10.1007/978-3-540-29925-7_9693. ISBN 978-3-540-00238-3.
  3. ^ a b c d e f "LCDB Data for (21873) Jindrichuvhradec". Asteroid Lightcurve Database (LCDB). Retrieved 17 May 2016.
  4. ^ a b "Asteroid 21873 Jindrichuvhradec – Nesvorny HCM Asteroid Families V3.0". Small Bodies Data Ferret. Retrieved 27 October 2019.
  5. ^ a b c "JPL Small-Body Database Browser: 21873 Jindrichuvhradec (1999 UU3)" (2017-03-27 last obs.). Jet Propulsion Laboratory. Retrieved 5 July 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. Retrieved 17 May 2016.
  7. ^ a b 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 3 December 2016.
  8. ^ a b c Waszczak, Adam; Chang, Chan-Kao; Ofek, Eran O.; Laher, Russ; Masci, Frank; Levitan, David; et al. (September 2015). "Asteroid Light Curves from the Palomar Transient Factory Survey: Rotation Periods and Phase Functions from Sparse Photometry". The Astronomical Journal. 150 (3): 35. arXiv:1504.04041. Bibcode:2015AJ....150...75W. doi:10.1088/0004-6256/150/3/75. Retrieved 17 May 2016.
  9. ^ a b c 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 17 May 2016.
  10. ^ a b Nesvorný, D.; Broz, M.; Carruba, V. (December 2014). Identification and Dynamical Properties of Asteroid Families. Asteroids IV. pp. 297–321. arXiv:1502.01628. Bibcode:2015aste.book..297N. doi:10.2458/azu_uapress_9780816532131-ch016. ISBN 9780816532131.
  11. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 17 May 2016.

External links[edit]