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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 byT. Urata
Discovery siteYakiimo Stn.
Discovery date12 March 1978
MPC designation(2090) Mizuho
Named after
Mizuho Urata
(daughter of discoverer)[2]
1978 EA · 1937 RE
1942 PG · 1951 EH
1952 HA4 · 1953 RT
1953 TP · 1959 VD
1964 TE · 1970 WV
1978 EJ
main-belt · (outer)[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc66.14 yr (24,157 days)
Aphelion3.4819 AU
Perihelion2.6635 AU
3.0727 AU
5.39 yr (1,967 days)
0° 10m 58.8s / day
Physical characteristics
18.185±0.117 km[5]
18.92±0.79 km[6]
35.28 km (calculated)[3]
5.47±0.01 h[7]
0.057 (assumed)[3]
Tholen = S[1] · S[3]
B–V = 0.871[1]
U–B = 0.499[1]

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 classificationEdit

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 characteristicsEdit

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

Rotation periodEdit

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 albedoEdit

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]


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 before November 1977 (M.P.C. 4482).[10]


  1. ^ a b c d e f g h "JPL Small-Body Database Browser: 2090 Mizuho (1978 EA)" (2017-05-02 last obs.). Jet Propulsion Laboratory. Retrieved 10 June 2017.
  2. ^ a b Schmadel, Lutz D. (2007). "(2090) Mizuho". Dictionary of Minor Planet Names – (2090) Mizuho. Springer Berlin Heidelberg. p. 169. doi:10.1007/978-3-540-29925-7_2091. ISBN 978-3-540-00238-3.
  3. ^ a b c d e f "LCDB Data for (2090) Mizuho". Asteroid Lightcurve Database (LCDB). Retrieved 7 December 2016.
  4. ^ a b c Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Dailey, J.; et al. (November 2011). "Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters". The Astrophysical Journal. 741 (2): 20. arXiv:1109.4096. Bibcode:2011ApJ...741...68M. doi:10.1088/0004-637X/741/2/68. Retrieved 7 December 2016.
  5. ^ a b c d Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90.
  6. ^ a b c d Usui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi; et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117. Retrieved 7 December 2016.
  7. ^ a b Brinsfield, James W. (October 2010). "Asteroid Lightcurve Analysis at the Via Capote Observatory: 2010 February-May". The Minor Planet Bulletin. 37 (4): 146–147. Bibcode:2010MPBu...37..146B. ISSN 1052-8091. Retrieved 7 December 2016.
  8. ^ a b "2090 Mizuho (1978 EA)". Minor Planet Center. Retrieved 7 December 2016.
  9. ^ Kosai, H.; Urata, T.; Nakamura, T. (December 1993). "Activities of Asteroid Studies by Amateur Astronomers in Japan". Seventy-five (75) Years of Hirayama Asteroid Families: The Role of Collisions in the Solar System History. Astronomical Society of the Pacific Conference Series. 63: 297. Bibcode:1994ASPC...63..297K. Retrieved 7 December 2016.
  10. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 7 December 2016.

External linksEdit