2090 Mizuho

2090 Mizuho, provisional designation 1978 EA, is a stony asteroid from the outer region of the asteroid belt, approximately 18 kilometers in diameter.

2090 Mizuho

Discovery[1]
Discovered by	T. Urata
Discovery site	Yakiimo Stn.
Discovery date	12 March 1978
Designations
MPC designation	(2090) Mizuho
Named after	Mizuho Urata (daughter of discoverer)[2]
Alternative designations	1978 EA · 1937 RE 1942 PG · 1951 EH 1952 HA4 · 1953 RT 1953 TP · 1959 VD 1964 TE · 1970 WV 1978 EJ
Minor planet category	main-belt · (outer)[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	66.14 yr (24,157 days)
Aphelion	3.4819 AU
Perihelion	2.6635 AU
Semi-major axis	3.0727 AU
Eccentricity	0.1332
Orbital period (sidereal)	5.39 yr (1,967 days)
Mean anomaly	337.47°
Mean motion	0° 10m 58.8s / day
Inclination	11.814°
Longitude of ascending node	339.85°
Argument of perihelion	341.20°
Physical characteristics
Dimensions	17.991±0.141[4] 18.185±0.117 km[5] 18.92±0.79 km[6] 35.28 km (calculated)[3]
Synodic rotation period	5.47±0.01 h[7]
Geometric albedo	0.057 (assumed)[3] 0.207±0.019[6] 0.2154±0.0435[5] 0.219±0.029[4]
Spectral type	Tholen = S[1] · S[3] B–V = 0.871[1] U–B = 0.499[1]
Absolute magnitude (H)	10.99[1][3][5][6]

The asteroid was discovered on 12 March 1978, by Japanese astronomer Takeshi Urata at the JCPM Yakiimo Station in Shimizu, Japan, who named it after his daughter, Mizuho Urata.^[8]

Orbit and classification

Mizuho orbits the Sun in the outer main-belt at a distance of 2.7–3.5 AU once every 5 years and 5 months (1,967 days). Its orbit has an eccentricity of 0.13 and an inclination of 12° with respect to the ecliptic.^[1]

The asteroid was first identified as 1937 RE at Simeiz Observatory. The first used observation was obtained at Heidelberg Observatory in 1951, extending the Mizuho's observation arc by 27 years prior to its official discovery observation.^[8]

Physical characteristics

In the Tholen classification, Mizuho is characterized as a common S-type asteroid.^[1]

Rotation period

In February 2010, a rotational lightcurve for Mizuho was obtained from photometric observations by James W. Brinsfield at the Via Capote Observatory (G69) in California. It gave a rotation period of 5.47 hours with a brightness variation of 0.30 magnitude (U=2+).^[7]

Diameter and albedo

According to the surveys carried out by the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Mizuho measures between 18.0 and 18.9 kilometers in diameter and its surface has an albedo of between 0.207 and 0.219, which is typical for stony asteroids.^[4][5][6] The Collaborative Asteroid Lightcurve Link, however assumes a standard albedo for a carbonaceous C-type asteroid of 0.057 and correspondingly calculates a much larger diameter of 35.3 kilometers.^[3]

Naming

The discoverer named this minor planet after his daughter, Mizuho Urata.^[2] It was the first asteroid in over 50 years to be discovered by a non-professional astronomer, which set off a wave of interest in amateur asteroid discovery, especially in Japan.^[9] The official naming citation was published by the Minor Planet Center on 1 September 1978 (M.P.C. 4482).^[10]