Discovery [1] | |
---|---|
Discovered by | N. Sato |
Discovery site | Chichibu Obs. |
Discovery date | 21 December 1997 |
Designations | |
(31179) Gongju | |
Named after |
Gongju
[1] (South Korean city) |
1997 YR2 · 1989 TM9 1999 CS56 | |
main-belt
[1]
[2] · (
inner) Nysa [3] [4] | |
Orbital characteristics [2] | |
Epoch 23 March 2018 ( JD 2458200.5) | |
Uncertainty parameter 0 | |
Observation arc | 28.39 yr (10,369 d) |
Aphelion | 2.9123 AU |
Perihelion | 1.9732 AU |
2.4427 AU | |
Eccentricity | 0.1922 |
3.82 yr (1,394 d) | |
192.32 ° | |
0° 15m 29.52s / day | |
Inclination | 3.4527° |
81.303° | |
248.25° | |
Physical characteristics | |
4.675±0.152
km
[5]
[6] 5.04 km (calculated) [3] | |
4.829±0.001 h [7] | |
0.21 (assumed)
[3] 0.353±0.028 [5] [6] | |
S ( SDSS-MOC) [3] [8] | |
13.4
[6] 13.8 [2] [3] | |
31179 Gongju ( provisional designation 1997 YR2) is a stony Nysian asteroid from the inner regions of the asteroid belt, approximately 5 kilometers (3 miles) in diameter. It was discovered on 21 December 1997, by Japanese amateur astronomer Naoto Sato at his Chichibu Observatory near Tokyo, central Japan. [1] The S-type asteroid has a rotation period of 4.8 hours and possibly an elongated shape. [3] It was named for the South Korean city of Gongju. [1]
Gongju is a member of the Nysa family ( 405), [3] [4] the largest asteroid family of the main belt, consisting of stony and carbonaceous subfamilies. The family, named after 44 Nysa, is located near the 3:1 orbital resonance with Jupiter, a depleted zone that separates the inner from the intermediate asteroid belt. [9]
It orbits the Sun in the inner asteroid belt at a distance of 2.0–2.9 AU once every 3 years and 10 months (1,394 days; semi-major axis of 2.44 AU). Its orbit has an eccentricity of 0.19 and an inclination of 3 ° with respect to the ecliptic. [2] The body's observation arc begins with its observations as 1989 TM9 at ESO's La Silla Observatory in October 1989, more than 8 years prior to its official discovery observation at Chichibu. [1]
Based on the Moving Object Catalog (MOC) of the Sloan Digital Sky Survey, Gongju has a spectral type of a stony S-type asteroid. [8]
In October 2012, a rotational lightcurve of Gongju was obtained from photometric observations by American astronomer John Ruthroff at the Shadowbox Observatory in Indiana. Lightcurve analysis gave a well-defined rotation period of 4.829 hours with a high brightness amplitude of 0.80 magnitude, indicative of a non-spherical shape ( U=3). [7]
According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Gongju measures 4.675 kilometers in diameter and its surface has an albedo of 0.353, [5] [6] while the Collaborative Asteroid Lightcurve Link assumes an albedo of 0.21 and calculates a diameter of 5.04 kilometers based on an absolute magnitude of 13.8. [3]
This minor planet was named after the South Korean city of Gongju, located in Chungcheongnam Province. It has a population of approximately 120,000 and was the capital of Baekje dynasty in the 5th century AD and the seat of the provincial government until 1932. [1] The official naming citation was published by the Minor Planet Center on 14 May 2014 ( M.P.C. 88406). [10]