5692 Shirao

5692 Shirao, provisional designation 1992 FR, is a stony Eunomia asteroid from the middle region of the asteroid belt, approximately 9 kilometers in diameter. It was discovered on 23 March 1992, by Japanese amateur astronomers Kin Endate and Kazuro Watanabe at Kitami Observatory, Hokkaidō, Japan.^[10] The asteroid was later named for Japanese geologist and astrophotographer Motomaro Shirao.^[2]

5692 Shirao

Discovery[1]
Discovered by	K. Endate K. Watanabe
Discovery site	Kitami Obs.
Discovery date	23 March 1992
Designations
MPC designation	(5692) Shirao
Named after	Motomaro Shirao (geologist, photographer)[2]
Alternative designations	1992 FR · 1949 KK 1966 FO · 1966 FS 1970 CH · 1976 SN2 1979 HT2 · 1979 HV1 1985 UW2 · 1989 SO9
Minor planet category	main-belt · Eunomia[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	67.83 yr (24,776 days)
Aphelion	3.1373 AU
Perihelion	2.1723 AU
Semi-major axis	2.6548 AU
Eccentricity	0.1818
Orbital period (sidereal)	4.33 yr (1,580 days)
Mean anomaly	287.13°
Mean motion	0° 13m 40.44s / day
Inclination	11.931°
Longitude of ascending node	181.78°
Argument of perihelion	44.251°
Physical characteristics
Dimensions	9.17 km (calculated)[3] 9.548±0.155[4] 9.75±0.30 km[5] 9.811±0.063 km[6]
Synodic rotation period	2.886±0.002 h[7] 2.8878±0.0004 h[a] 2.90±0.02 h (ii)[8]
Geometric albedo	0.21 (assumed)[3] 0.2218±0.0290[6] 0.223±0.030[4][5]
Spectral type	S[3][9]
Absolute magnitude (H)	12.3[5][6] · 12.47±0.25[9] · 12.5[1][3]

Orbit and classification

Shirao is a member of the Eunomia family, a large group of stony asteroids and the most prominent family in the intermediate main-belt. It orbits the Sun in the central main-belt at a distance of 2.2–3.1 AU once every 4 years and 4 months (1,580 days). Its orbit has an eccentricity of 0.18 and an inclination of 12° with respect to the ecliptic.^[1]

In 1949, it was first identified as 1949 KK at Goethe Link Observatory. The body's observation arc begins in 1955, with a precovery at Palomar Observatory, 37 years prior to its official discovery observation at Kitami.^[10]

Physical characteristics

Rotation period

In June 2014, a rotational lightcurve of Shirao was obtained from photometric observations made by American astronomer Brian Warner at his Palmer Divide Observatory (716) in Colorado. It gave a well-defined rotation period of 2.8878 hours with a brightness variation of 0.16 magnitude (U=3).^[a]

Previous lightcurves were obtained by French astronomer René Roy (2.90 hours, Δ 0.13 mag, U=2) in June 2001,^[8] by American astronomer Donald P. Pray (2.886 hours, Δ 0.12 mag, U=2) in March 2005,^[7] and by astronomers Dominique Suys, Hugo Riemis and Jan Vantomme (2.90 hours, Δ 0.15 mag, U=2+) in September 2006.^[3][8]

Diameter and albedo

According to the surveys carried out by NASA's Wide-field Infrared Survey Explorer and its subsequent NEOWISE mission, Shirao measures between 9.5 and 9.8 kilometers in diameter and its surface has an albedo of 0.22,^[4][5][6] while the Collaborative Asteroid Lightcurve Link assumes a standard albedo of 0.21 – derived from 15 Eunomia, the largest member and namesake of this asteroid family – and calculates a diameter of 9.2 kilometers.^[3]

Naming

This minor planet was named after Motomaro Shirao (born 1953), a Japanese geologist and astrophotographer, who is known for his photographs of volcanoes and lunar geological features.^[2] The official naming citation was published by the Minor Planet Center on 4 April 1996 (M.P.C. 26930).^[11]

Notes

1. Warner (2014l) web: rotation period 2.8878±0.0004 hours with a brightness amplitude of 0.16 mag. Summary figures for (5692) Shirao at Collaborative Asteroid Lightcurve Link (CALL) and (2014MPBu...41..235P)