| Discovery[1] | |
|---|---|
| Discovered by | J. Tichá M. Tichý |
| Discovery site | Kleť Obs. |
| Discovery date | 29 October 1999 |
| Designations | |
| (21873) Jindřichůvhradec | |
Named after | Jindřichův Hradec[2] (Czech town) |
| 1999 UU3 · 1982 SN8 1988 XA5 | |
| main-belt · (outer)[3] Hygiea[4] | |
| Orbital characteristics[5] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 34.52 yr (12,608 days) |
| Aphelion | 3.8041AU |
| Perihelion | 2.4999 AU |
| 3.1520 AU | |
| Eccentricity | 0.2069 |
| 5.60yr (2,044 days) | |
| 89.398° | |
| 0° 10m 33.96s / day | |
| Inclination | 4.4633° |
| 238.03° | |
| 130.91° | |
| Physical characteristics | |
| Dimensions | 7.183±0.136 km[6][7] 10.44 km(calculated)[3] |
| 50.5874±0.0664 h[8] | |
| 0.057(assumed)[3] 0.237±0.088[6][7] | |
| 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 designation1999 UU3) is a dark Hygieanasteroid and relativelyslower-than average rotator from the outer region of theasteroid belt, approximately 8 kilometers (5.0 miles) in diameter.
It was discovered by Czech astronomersJana Tichá andMiloš Tichý at the South BohemianKleť Observatory on 29 October 1999, and named for the Czech town ofJindřichův Hradec.[1]
The asteroid is a member of theHygiea family (601),[4] a very largefamily of carbonaceous outer-belt asteroids, named after thefourth-largest asteroid,10 Hygiea.[10] It orbits the Sun in theouter main-belt at a distance of 2.5–3.8 AU once every 5 years and 7 months (2,044 days). Its orbit has aneccentricity of 0.21 and aninclination of 4° with respect to theecliptic.[5] The firstprecovery was obtained atCrimea–Nauchnij in 1982, extending the asteroid'sobservation arc by 17 years prior to its discovery.[1]
According to the survey carried out by theNEOWISE mission of NASA's space-basedWide-field Infrared Survey Explorer, the asteroid measures 7.2 kilometers in diameter and its surface has analbedo of 0.23.[6] Based on anabsolute magnitude of 13.63, theCollaborative Asteroid Lightcurve Link calculates a diameter of 10.4 kilometers, assuming a standard albedo for carbonaceousC-type asteroids of 0.057,[3] which is in-line with the Hygiea family's overallspectral type.[10]: 23 A large-scale survey byPan-STARRS, however, classifies the body as anX-type asteroid, which metallic core group has an intermediate albedo betweenstony and carbonaceous bodies.[9]
In September 2010, a photometriclightcurve analysis at the U.S.Palomar Transient Factory, California, gave a longrotation period of50.5874±0.0664 hours with a brightness variation of 0.61 inmagnitude (U=2).[8] This makes it a relativelyslow rotator for an asteroid of its size, which normally have periods of just a few hours rather than several days.
Thisminor planet was named afterJindřichův 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 ofGreenwich. A line marks the course of the meridian in its paving stones.[2] The approved naming citation was published by theMinor Planet Center on 28 January 2002 (M.P.C. 44595).[11]
