1999 Hirayama
| Discovery | |
|---|---|
| Discovered by | L. Kohoutek |
| Discovery site | Bergedorf Obs. |
| Discovery date | 27 February 1973 |
| Designations | |
| MPC designation | (1999) Hirayama |
|
Named after
|
Kiyotsugu Hirayama (astronomer) |
| 1973 DR · 1935 GF 1940 EH · 1951 EY1 1951 FA · 1965 UF 1969 NB · 1975 NE |
|
| main-belt · (outer) | |
| Orbital characteristics | |
| Epoch 16 February 2017 (JD 2457800.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 76.07 yr (27,783 days) |
| Aphelion | 3.4719 AU |
| Perihelion | 2.7576 AU |
| 3.1147 AU | |
| Eccentricity | 0.1147 |
| 5.50 yr (2,008 days) | |
| 3.6085° | |
| 0° 10m 45.48s / day | |
| Inclination | 12.533° |
| 148.04° | |
| 356.97° | |
| Physical characteristics | |
| Dimensions | 33.77 km (derived) 33.95±2.1 km 35.68±0.55 km 38.28±0.40 km |
|
13.5921±0.0003 h 15.63±0.01 h 22.37±0.03 h |
|
|
0.053±0.005 0.0617 (derived) 0.082±0.003 0.0882±0.012 |
|
| C | |
| 10.6 · 10.78±0.31 · 10.90 · 11.0 | |
1999 Hirayama, provisional designation 1973 DR, is a carbonaceous asteroid from the outer region of the asteroid belt, approximately 34 kilometers in diameter. It was discovered on 27 February 1973, by Czech astronomer Luboš Kohoutek at the Hamburger Bergedorf Observatory in Germany, and later named after Japanese astronomer Kiyotsugu Hirayama.
Hirayama orbits the Sun at a distance of 2.8–3.5 AU once every 5 years and 6 months (2,008 days). Its orbit has an eccentricity of 0.11 and an inclination of 13° with respect to the ecliptic. The spectrum of Hirayama matches a C-type classification on the Tholen taxonomic schem, but with a "broad absorption band that can be associated to a process of aqueous alteration". That is, the surface appears to show some form of water modification.
A rotational lightcurve of Hirayama was obtained at the Menke Observatory in February 2002. It showed a periodicity of 15.63±0.01 hours, during which time the brightness of Hirayama varies by 0.45±0.04 in magnitude (U=3-). At the same time, photometric observations by astronomers Roberto Crippa and Federico Manzini gave a rotation period of 22.37 hours and a brightness variation of 0.47 magnitude (U=2). These results supersede an observation from January 2005, by Hiromi and Hiroko Hamanowa at their Hamanowa Astronomical Observatory, Japan, that gave a shorter period of 13.59 hours with an amplitude of 0.57 magnitude.(U=n.a.).
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