4959 Niinoama

4959 Niinoama (prov. designation: 1991 PA1) is a dark background asteroid from the outer regions of the asteroid belt. It was discovered by Japanese astronomers Akira Natori and Takeshi Urata at JCPM Yakiimo Station on 15 August 1991.[10] The presumed carbonaceous C-type asteroid has a rotation period of 4.7 hours and measures approximately 36 kilometers (22 miles) in diameter. It was named after Taira no Tokiko (1126–1185) of the Imperial House of Japan during the Heian period.

4959 Niinoama
004959-asteroid shape model (4959) Niinoama.png
Shape model of Niinoama from its lightcurve
Discovery [1]
Discovered byA. Natori
T. Urata
Discovery siteJCPM Yakiimo Stn.
Discovery date15 August 1991
(4959) Niinoama
Named after
Taira no Tokiko
(Imperial House of Japan)[2]
1991 PA1 · 1958 TZ
1966 CB · 1968 MC
1972 EB · 1979 OU13
1980 TG1 · 1980 TS8
1984 OO · 1985 OD
1986 VS1 · 1989 FE1
main-belt · (outer)[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc67.15 yr (24,528 days)
Aphelion3.1759 AU
Perihelion3.1272 AU
3.1516 AU
5.59 yr (2,044 days)
0° 10m 34.32s / day
Physical characteristics
Mean diameter
26.50±0.73 km[4]
27.96±2.4 km[5]
35.842±0.117 km[6]
36.21±0.80 km[7]
42.507±0.576 km[8]
4.73±0.01 h[9]
0.1081 (derived)[3]
C (assumed)[3]
10.8[3][4][5][7][8] · 10.9[1]

Orbit and classificationEdit

Niinoama is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. It orbits the Sun in the outer main-belt at a distance of 3.1–3.2 AU once every 5 years and 7 months (2,044 days). Its orbit has an eccentricity of 0.01 and an inclination of 9° with respect to the ecliptic.[1] A first precovery was taken at Palomar Observatory in May 1950, extending the body's observation arc by more than 41 years prior to its official discovery observation at Yakiimo.[10]


This minor planet was named after Taira no Tokiko (1126–1185), second wife of military leader Taira no Kiyomori and grandmother of Emperor Antoku after whom 3686 Antoku is named. According to the Tale of the Heike, she drowned herself during the Battle of Dan-no-ura together with the boy-Emperor Antoku in her arms.[2][11] The official naming citation was published by the Minor Planet Center on 10 November 1992 (M.P.C. 21132).[12]

Physical characteristicsEdit

Niinoama is an assumed C-type asteroid.[3]


Photometric observations of Niinoama collected during 2008 show a rotation period of 4.73±0.01 hours with a brightness variation of 0.32 ± 0.04 magnitude (U=3),[9] superseding an early measurement that gave 4.725±0.002 hours (U=1+).[13]

Diameter and albedoEdit

According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Niinoama measures between 26.50 and 42.51 kilometers in diameter and its surface has an albedo of 0.079.[5][7][8][4] The Collaborative Asteroid Lightcurve Link adopts a diameter of 27.96 kilometers from IRAS, and derives an albedo of 0.1082 based on an absolute magnitude of 10.8.[3]


  1. ^ a b c d "JPL Small-Body Database Browser: 4959 Niinoama (1991 PA1)" (2017-07-05 last obs.). Jet Propulsion Laboratory. Retrieved 16 August 2017.
  2. ^ a b Schmadel, Lutz D. (2007). "(4959) Niinoama". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 427. doi:10.1007/978-3-540-29925-7_4838. ISBN 978-3-540-00238-3.
  3. ^ a b c d e f "LCDB Data for (4959) Niinoama". Asteroid Lightcurve Database (LCDB). Retrieved 16 August 2017.
  4. ^ a b c d Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Nugent, C.; et al. (November 2012). "Preliminary Analysis of WISE/NEOWISE 3-Band Cryogenic and Post-cryogenic Observations of Main Belt Asteroids". The Astrophysical Journal Letters. 759 (1): 5. arXiv:1209.5794. Bibcode:2012ApJ...759L...8M. doi:10.1088/2041-8205/759/1/L8.
  5. ^ a b c d Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System. 12: IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 22 October 2019.
  6. ^ a b Masiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; et al. (August 2014). "Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos". The Astrophysical Journal. 791 (2): 11. arXiv:1406.6645. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121.
  7. ^ 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. (online, AcuA catalog p. 153)
  8. ^ 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.
  9. ^ a b Carbo, Landy; Kragh, Katherine; Krotz, Jonathan; Meiers, Andrew; Shaffer, Nelson; Torno, Steven; et al. (July 2009). "Asteroid Lightcurve Analysis at the Oakley Southern Sky Observatory and Oakley Observatory: 2008 September and October" (PDF). Minor Planet Bulletin. 36 (3): 91–94. Bibcode:2009MPBu...36...91C. Retrieved 19 March 2020.
  10. ^ a b "4959 Niinoama (1991 PA1)". Minor Planet Center. Retrieved 16 August 2017.
  11. ^ McCullough, Helen Craig (1988). The Tale of the Heike. Stanford University Press. pp. 377–78. ISBN 9780804718035.
  12. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 16 August 2017.
  13. ^ Behrend, Raoul. "Asteroids and comets rotation curves – (4959) Niinoama". Geneva Observatory. Retrieved 16 August 2017.

External linksEdit