Discovered by T. Nomura
K. Kawanishi MPC designation 4797 Ako Discovered 30 September 1989 Asteroid family Nysa family Asteroid group Asteroid belt | Discovery date 30 September 1989 Minor planet category main-belt · Nysa Orbits Sun Discovery site Minami-Oda Observatory | |
Named after Akō, Hyōgo
(Japanese city) Alternative names 1989 SJ · 1978 VY9
1985 QB4 Discoverers Toshiro Nomura, Kōyō Kawanishi Similar Sun, 135 Hertha, 142 Polana, 9922 Catcheller | ||
4797 Ako, provisional designation 1989 SJ, is a stony Nysian asteroid from the inner regions of the asteroid belt, approximately 5 kilometers in diameter. It was discovered by the Japanese astronomers Toshiro Nomura and Kōyō Kawanishi at the Minami-Oda Observatory, Japan, on 30 September 1989.
The S-type asteroid is a member of the stony subgroup of the main-belt's Nysa family, which is named after its largest member 44 Nysa. It orbits the Sun at a distance of 2.0–2.9 AU once every 3 years and 9 months (1,368 days). Its orbit has an eccentricity of 0.18 and an inclination of 2° with respect to the ecliptic. The first precovery was taken at Palomar Observatory in 1978, extending the asteroid's observation arc by 11 years prior to its discovery.
A rotational light-curve of this asteroid was obtained for the first time from photometric observations made at the U.S. Ricky Observatory, Missouri, in November 2008. It gave a well-defined rotation period of 7000408500000000000♠4.085±0.001 hours with a relatively high brightness variation of 0.90 in magnitude (U=3), indicative of a non-spheroidal shape.
According to NASA's space-based Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, the asteroid measures 6.0 kilometers in diameter and its surface has an albedo of 0.11, while the Collaborative Asteroid Lightcurve Link (CALL) assumes a standard albedo for stony asteroids of 0.21, and calculates a diameter of 4.0 kilometers, as the higher the albedo (reflectivity), the smaller the body's diameter, at a constant absolute magnitude (brightness).
The minor planet was named for the city of Akō in the Hyōgo Prefecture, Japan, and for its ancient castle on the Seto Inland Sea. Known for its salt production, the city is the birthplace of the fictional account of Chūshingura, a tale about the forty-seven Ronin who committed seppuku after avenging their master. Ako is also the home of the second discoverer's private Minami-Oda observatory, where Kōyō Kawanishi observes small Solar System bodies. Naming citation was published on 27 June 1991 (M.P.C. 18465).