7803 Adachi

7803 Adachi, provisional designation 1997 EW₂, is a stony Agnia asteroid from the middle region of the asteroid belt, approximately 6.4 kilometers (4 miles) in diameter. The asteroid was discovered on 4 March 1997, by Japanese amateur astronomer Takao Kobayashi at the Ōizumi Observatory in central Japan. It was named for Japanese amateur astronomer Makoto Adachi.^[1] The S-type asteroid has a rotation period of 5.2 hours.^[6]

7803 Adachi

Discovery[1]
Discovered by	T. Kobayashi
Discovery site	Ōizumi Obs.
Discovery date	4 March 1997
Designations
MPC designation	(7803) Adachi
Named after	Makoto Adachi[1] (amateur astronomer)
Alternative designations	1997 EW2 · 1973 AA3 1976 UY17 · 1978 EM1 1992 CF2
Minor planet category	main-belt[1][2] · (middle) Agnia[3]
Orbital characteristics[2]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc	63.96 yr (23,363 d)
Aphelion	2.9253 AU
Perihelion	2.6459 AU
Semi-major axis	2.7856 AU
Eccentricity	0.0502
Orbital period (sidereal)	4.65 yr (1,698 d)
Mean anomaly	239.11°
Mean motion	0° 12m 43.2s / day
Inclination	4.9969°
Longitude of ascending node	110.63°
Argument of perihelion	8.8759°
Physical characteristics
Dimensions	6.359±0.129 km[4][5] 10.31 km (calculated)[6]
Synodic rotation period	5.1966±0.0082 h[7]
Geometric albedo	0.057 (assumed)[6] 0.251±0.055[4][5]
Spectral type	S[8] · C (generic)[6]
Absolute magnitude (H)	13.1[4] · 13.212±0.005 (R)[7] · 13.3[2] · 13.65±0.27[8] · 13.66[6]

Orbit and classification

Adachi is a member of the Agnia family (514),^[3][9] a very large family of stony asteroids with more than 2000 known members.^[10] They most likely formed from the breakup of a basalt object, which in turn was spawned from a larger parent body that underwent igneous differentiation.^[9] The family's parent body and namesake is the asteroid 847 Agnia.^[10]

It orbits the Sun in the central asteroid belt at a distance of 2.6–2.9 AU once every 4 years and 8 months (1,698 days; semi-major axis of 2.79 AU). Its orbit has an eccentricity of 0.05 and an inclination of 5° with respect to the ecliptic.^[2] The first precovery was taken at the U.S. Palomar Observatory in 1953, extending the asteroid's observation arc by 44 years prior to it discovery.^[1]

Physical characteristics

Adachi has been characterized as a stony S-type asteroid by Pan-STARRS photometric survey,^[8] which agrees with the Agnia family's overall spectral type.^{[10] : 23}

Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Adachi measures 6.359 kilometers in diameter and its surface has an albedo between 0.251 and 0.2513.^[4][5] The Collaborative Asteroid Lightcurve Link assumes a generic, carbonaceous albedo of 0.057 for all minor planets with a semi-major axis of more than 2.7 AU, and consequently calculates a larger diameter of 10.31 kilometers using an absolute magnitude of 13.66.^[6]

Rotation period

In August 2013, a rotational lightcurve of Adachi was obtained through photometric observations at the Palomar Transient Factory in California. It showed a period of 5.1966 hours with a brightness variation of 0.31 magnitude (U=2).^[7]

Naming

This minor planet was named after Makoto Adachi (born 1953), Japanese amateur astronomer and elementary school teacher from Kyoto. He is the director of the Oriental Astronomical Association and a long-time direct observer of the Solar System's planets, especially Jupiter.^[1] The approved naming citation was published by the Minor Planet Center on 6 August 2003 (M.P.C. 49279).^[11]