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6709 Hiromiyuki, provisional designation 1989 CD, is a background or Florian asteroid from the inner regions of the asteroid belt, approximately 4 kilometers (2.5 miles) in diameter. It was discovered on 2 February 1989, by Japanese amateur astronomers Masaru Arai and Hiroshi Mori at the Yorii Observatory in Japan.[1] The possibly elongated S-type asteroid has a rotation period of 6.8 hours.[5] It was named after the Hiroshi Mori's children, Hiroyuki and Miyuki.[1]

6709 Hiromiyuki
Discovery [1]
Discovered byM. Arai
H. Mori
Discovery siteYorii Obs.
Discovery date2 February 1989
MPC designation(6709) Hiromiyuki
Named after
Hiroyuki and Miyuki
(Discoverer's children)
1989 CD · 1955 SX
1973 UM3 · 1991 RX7
main-belt[1][2] · (inner)
background[3][4] · Flora[5]
Orbital characteristics[2]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc62.44 yr (22,808 d)
Aphelion2.7247 AU
Perihelion1.9728 AU
2.3488 AU
3.60 yr (1,315 d)
0° 16m 25.68s / day
Physical characteristics
Mean diameter
3.975±0.519 km[6]
4.50 km (calculated)[5]
6.828±0.001 h[7]
0.24 (assumed)[5]
S (assumed)[5]

Orbit and classificationEdit

Hiromiyuki is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.[3][4] Based on osculating Keplerian orbital elements, the asteroid has also been classified as a member of the Flora family (402), a giant asteroid family and the largest family of stony asteroids in the main-belt.[5]

Hiromiyuki orbits the Sun in the inner asteroid belt at a distance of 2.0–2.7 AU once every 3 years and 7 months (1,315 days; semi-major axis of 2.35 AU). Its orbit has an eccentricity of 0.16 and an inclination of 2° with respect to the ecliptic.[2] The body's observation arc begins with its first observation as 1955 SX at Goethe Link Observatory in September 1955, more than 33 years prior to its official discovery observation at Yorii.[1]

Physical characteristicsEdit

Hiromiyuki is an assumed S-type asteroid based on its classification into the Flora family.[5]

Rotation periodEdit

In February 2007, a rotational lightcurve of Hiromiyuki was obtained from photometric observations by Donald P. Pray at Carbuncle Hill Observatory (912), in collaboration with Adrián Galád, Marek Husárik, and Julian Oey. Lightcurve analysis gave a rotation period of 6.828 hours with an exceptionally high brightness amplitude of 1.00±0.02 magnitude (U=3), which typically indicates that the body has an elongated shape.[5][7]

Diameter and albedoEdit

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Hiromiyuki measures 3.98 kilometers in diameter and its surface has a high albedo of 0.34.[6] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.24 – derived from 8 Flora, the parent body of the Flora family – and calculates a diameter of 4.50 kilometers based on an absolute magnitude of 13.9.[5]


This minor planet was named after Hiroyuki (born 1991) and Miyuki Mori (born 1993), son and daughter of the second co-discoverer Hiroshi Mori.[1] The official naming citation was published by the Minor Planet Center on 6 March 2004 (M.P.C. 51186).[8]


  1. ^ a b c d e f "6709 Hiromiyuki (1989 CD)". Minor Planet Center. Retrieved 3 May 2018.
  2. ^ a b c d "JPL Small-Body Database Browser: 6709 Hiromiyuki (1989 CD)" (2018-02-27 last obs.). Jet Propulsion Laboratory. Retrieved 3 May 2018.
  3. ^ a b "Small Bodies Data Ferret". Nesvorny HCM Asteroid Families V3.0. Retrieved 3 May 2018.
  4. ^ a b "Asteroid 6709 Hiromiyuki – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 29 October 2019.
  5. ^ a b c d e f g h i j "LCDB Data for (6709) Hiromiyuki". Asteroid Lightcurve Database (LCDB). Retrieved 3 May 2018.
  6. ^ a b c d Nugent, C. R.; Mainzer, A.; Masiero, J.; Bauer, J.; Cutri, R. M.; Grav, T.; et al. (December 2015). "NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos" (PDF). The Astrophysical Journal. 814 (2): 13. arXiv:1509.02522. Bibcode:2015ApJ...814..117N. doi:10.1088/0004-637X/814/2/117. Retrieved 3 May 2018.
  7. ^ a b Pray, Donald P.; Galad, Adrian; Husarik, Marek; Oey, Julian (March 2008). "Lightcurve Analysis of Fourteen Asteroids". The Minor Planet Bulletin. 35 (1): 34–36. Bibcode:2008MPBu...35...34P. ISSN 1052-8091. Retrieved 3 May 2018.
  8. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 3 May 2018.

External linksEdit