2478 Tokai

2478 Tokai, provisionally designated 1981 JC, is a stony Florian asteroid and binary system from the inner regions of the asteroid belt, approximately 10 kilometers in diameter. It was discovered on 4 May 1981, by Japanese astronomer Toshimasa Furuta at Tōkai Observatory (879), Japan.^[14] The asteroid was named after the city of Tōkai.^[2]

2478 Tokai

Discovery[1]
Discovered by	T. Furuta
Discovery site	Tōkai Obs. (879)
Discovery date	4 May 1981
Designations
MPC designation	(2478) Tokai
Pronunciation	/ˈtoʊkaɪ/ Japanese: [toːkai]
Named after	Tōkai (Japanese city)[2]
Alternative designations	1981 JC · 1931 HH 1932 SE · 1934 ED 1939 VH · 1951 JP 1955 OE · 1955 QV 1957 BD · 1972 RS 1978 NU2 · 1979 XR 1981 JT
Minor planet category	main-belt · Flora[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	84.68 yr (30,929 days)
Aphelion	2.3781 AU
Perihelion	2.0740 AU
Semi-major axis	2.2261 AU
Eccentricity	0.0683
Orbital period (sidereal)	3.32 yr (1,213 days)
Mean anomaly	103.28°
Mean motion	0° 17m 48.48s / day
Inclination	4.1389°
Longitude of ascending node	228.80°
Argument of perihelion	233.85°
Known satellites	1[3][4][5]
Physical characteristics
Dimensions	9.238±0.112 km[6] 9.36±1.51 km[7] 9.71±0.49 km[8] 9.982±0.031 km[9] 10.087 km[10] 10.09 km (taken)[3]
Synodic rotation period	25.88±0.01 h[a] 25.885±0.007 h[11] 25.8913 h[b] 25.97±0.11 h[12]
Geometric albedo	0.144±0.015[8] 0.1957[10] 0.2084±0.0371[9] 0.252±0.045[6] 0.33±0.20[7]
Spectral type	SMASS = S[1] · S[3]
Absolute magnitude (H)	11.88±0.03 (R)[b] · 12.00[7] · 12.15±0.04[13] · 12.2[1] · 12.33[9] · 12.37±0.058[3][10] · 12.80[8]

Orbit and classification

Tokai is a member of the Flora family, one of the largest groups of stony asteroids in the main-belt. It orbits the Sun in the inner main-belt at a distance of 2.1–2.4 AU once every 3 years and 4 months (1,213 days). Its orbit has an eccentricity of 0.07 and an inclination of 4° with respect to the ecliptic.^[1]

Physical characteristics

In the SMASS classification, Tokai is a common S-type asteroid.^[1]

Diameter and albedo

According to the surveys carried out by the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer (WISE) with its subsequent NEOWISE mission, Tokai measures between 9.238 and 9.982 kilometers in diameter and its surface has an albedo between 0.144 and 0.33.^[6][7][8][9] The Collaborative Asteroid Lightcurve Link agrees with Petr Pravec's revised WISE-data, that is, an albedo of 0.1957 and a diameter of 10.09 kilometers with an absolute magnitude of 12.37.^[3]

Satellite

Photometric observations in 2007, revealed a minor-planet moon in orbit of Tokai. It measures approximately 6 kilometers in diameter (lower limit diameter ratio of 0.72) and has an orbital period of 25.88 hours.^[3][4][5]

Naming

This minor planet was named after the city of Tōkai, Japan, where the discoverer lives and the discovering observatory is located.^[2] The approved naming citation was published by the Minor Planet Center on 8 February 1982 (M.P.C. 6650).^[15]

Notes

1. Oey (2011) web: rotation period 25.88 hours with a brightness amplitude of mag. Summary figures for (2478) Tokai at Collaborative Asteroid Lightcurve Link (CALL)
2. Pravec (2007) web: rotation period 25.8913 hours with a brightness amplitude of 0.41 mag. Q=3. Summary figures for (2478) Tokai at Collaborative Asteroid Lightcurve Link (CALL)