Discovered by J. TicháM. Tichý MPC designation 21873 Jindřichůvhradec Discovered 29 October 1999 Discoverers Jana Tichá, Miloš Tichý | Discovery date 29 October 1999 Minor planet category main-belt · (outer) Orbits Sun Asteroid group Asteroid belt | |
Alternative names 1999 UU3 · 1982 SN81988 XA5 People also search for Sun, 136666 Seidel, 74024 Hrabě | ||
21873 Jindřichůvhradec, provisional designation 1999 UU3, is a dark asteroid and relatively slow rotator from the outer region of the asteroid belt, approximately 8 kilometers in diameter. It was discovered by Czech astronomers Jana Tichá and Miloš Tichý at the South Bohemian Kleť Observatory on 29 October 1999.
The asteroid orbits the Sun at a distance of 2.5–3.8 AU once every 5 years and 7 months (2,045 days). Its orbit has an eccentricity of 0.21 and an inclination of 4° with respect to the ecliptic. The first precovery was obtained at Crimea–Nauchnij in 1982, extending the asteroid's observation arc by 17 years prior to its discovery.
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. The Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous C-type asteroids of 0.057, and calculates a diameter of 10.4 kilometers, as the lower the albedo, the larger a body's diameter, at a constant absolute magnitude. 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. In September 2010, a photometric light-curve analysis at the U.S. Palomar Transient Factory, California, gave a long rotation period of 7001505874000000000♠50.5874±0.0664 hours with a brightness variation of 0.61 in magnitude (U=2). 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.
The minor planet is named for 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. Naming citation was published on 28 January 2002 (M.P.C. 44595).