1185 Nikko

1185 Nikko, provisional designation 1927 WC, is a stony asteroid from the inner regions of the asteroid belt, approximately 10 kilometers in diameter. It was discovered on 17 November 1927 by Okuro Oikawa at the Tokyo Astronomical Observatory, Japan.^[11] The asteroid was named after the Japanese city of Nikkō.^[2]

1185 Nikko

Discovery[1]
Discovered by	O. Oikawa
Discovery site	Tokyo Astronomical Obs. (389)
Discovery date	17 November 1927
Designations
MPC designation	(1185) Nikko
Named after	Nikkō (Japanese city)[2]
Alternative designations	1927 WC · 1930 SE1 1930 SG1 · 1930 SH1
Minor planet category	main-belt · (inner)[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	86.78 yr (31,697 days)
Aphelion	2.4744 AU
Perihelion	2.0006 AU
Semi-major axis	2.2375 AU
Eccentricity	0.1059
Orbital period (sidereal)	3.35 yr (1,222 days)
Mean anomaly	280.93°
Mean motion	0° 17m 40.2s / day
Inclination	5.7013°
Longitude of ascending node	71.904°
Argument of perihelion	1.9614°
Physical characteristics
Dimensions	8.347±0.297 km[4] 11.35 km (calculated)[3] 12.56±0.83 km[5]
Synodic rotation period	3.781±0.0326[6] 3.78615±0.00005 h[7] 3.788±0.0326 h[6] 3.7889±0.0004 h[8] 3.79±0.01 h[9] 3.792±0.002 h[8]
Geometric albedo	0.164±0.023[5] 0.20 (assumed)[3] 0.370±0.041[4]
Spectral type	S (Tholen)[1] · S (SMASS)[1] S[3] B–V = 0.923[1] U–B = 0.514[1]
Absolute magnitude (H)	11.674±0.002 (R)[6] · 11.99±0.33[10] · 12.09[1][3][4][5]

Orbit and classification

Nikko orbits the Sun in the inner main-belt at a distance of 2.0–2.5 AU once every 3 years and 4 months (1,222 days). Its orbit has an eccentricity of 0.11 and an inclination of 6° with respect to the ecliptic.^[1] Nikko's observation arc begins with its first used observation taken at Johannesburg Observatory in 1930, or 3 years after its official discovery observation at Tokyo.^[11]

Physical characteristics

In both the Tholen and SMASS taxonomy, Nikko is a common stony S-type asteroid.^[1]

Rotation period

Between 2004 and 2011, several rotational lightcurves of Nikko were obtained from photometric observations taken by astronomers Laurent Bernasconi,^[8] Hiromi and Hiroko Hamanowa,^[8] John Menke,^[12] Robert Stephens,^[9] as well as at the Palomar Transient Factory in California.^[6] Lightcurve analysis gave a rotation period between 3.781 and 3.792 hours with a brightness variation between 0.26 and 0.50 magnitude (U=3/3/3/3-/2/2).^[3]

Diameter and albedo

According to the survey carried out by the Japanese Akari satellite and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Nikko measures 8.347 and 12.56 kilometers in diameter, and its surface has an albedo of 0.370 and 0.164, respectively.^[4][5] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 11.35 kilometers with an absolute magnitude of 12.09.^[3]

Naming

This minor planet was named for the Japanese city of Nikkō, located in the Tochigi Prefecture of central Japan. The tourist resort is known for its Shinto shrine and a UNESCO World Heritage Site Nikkō Tōshō-gū. The official naming citation was published by Paul Herget in The Names of the Minor Planets in 1955 (H 110).^[2][13]