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16525 Shumarinaiko

16525 Shumarinaiko, provisional designation 1991 CU2, is a stony Nysian asteroid and synchronous binary system from the inner regions of the asteroid belt, approximately 5 kilometers in diameter. It was discovered on 14 February 1991, by Japanese astronomers Kin Endate and Kazuro Watanabe at the Kitami Observatory on the island of Hokkaidō in northern Japan.[12] The asteroid was named after the Japanese Lake Shumarinai.[2] Its sub-kilometer sized minor-planet moon was discovered in 2013.

16525 Shumarinaiko
Discovery [1]
Discovered byK. Endate
K. Watanabe
Discovery siteKitami Obs.
Discovery date14 February 1991
MPC designation(16525) Shumarinaiko
Named after
Lake Shumarinai[2]
(Japanese lake)
1991 CU2 · 1996 TE51
main-belt · (inner)[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc67.29 yr (24,578 days)
Aphelion2.7341 AU
Perihelion2.0648 AU
2.3995 AU
3.72 yr (1,358 days)
0° 15m 54.72s / day
Known satellites1 (D: 0.83 km; P: 14.409 h)[5][6][a]
Physical characteristics
Dimensions5.253±0.146 km[7][8]
5.66 km (calculated)[3]
2.5932±0.0003 h[6]
2.6425±0.0006 h (poor)[9]
8.8±0.3 h (poor)[10]
0.20 (assumed)[3]
S (assumed)[3]
13.3[8] · 13.6[1][3] · 14.37±0.56[11]

Orbit and classificationEdit

Shumarinaiko is a member of the Nysa family (405),[3][4] the largest asteroid family of the main belt, consisting of stony and carbonaceous subfamilies. The family, named after 44 Nysa, is located in the inner belt near the Kirkwood gap (3:1 orbital resonance with Jupiter), a depleted zone that separates the central main belt.[13]

It orbits the Sun in the inner asteroid belt at a distance of 2.1–2.7 AU once every 3 years and 9 months (1,358 days). Its orbit has an eccentricity of 0.14 and an inclination of 2° with respect to the ecliptic.[1]

The body's observation arc begins with a precovery from the Digitized Sky Survey. It was taken at Palomar Observatory in March 1950, almost 41 years prior to the asteroid's official discovery observation at Kitami in 1991.[12]

Physical characteristicsEdit

Shumarinaiko is an assumed stony S-type asteroid.[3]

Rotation periodEdit

In January 2013, a rotational lightcurve of Shumarinaiko was obtained from photometric observations by Brian Warner at the Palmer Divide Observatory (716) in Colorado, and Dan Coley at DanHenge Observatory (U80) in California. Analysis of the bimodal lightcurve gave a well-defined rotation period of 2.5932 hours with a brightness amplitude of 0.08 magnitude (U=3),[6][a] superseding the results from previous observations that gave a period of 2.6425 and 8.8 hours, respectively (U=1/1).[9][10] A low brightness amplitude typically indicates that the body is rather spherical in shape.


During the photometric observation by Warner and Coley in January 2013 (see above), mutual occultation and eclipsing events revealed that Shumarinaiko is a synchronous binary asteroid with an elongated minor-planet moon in orbit. The satellite, provisionally designated S/2013 (16525) 1, seems to be tidally locked to its orbital period of 14.409 hours. It measures least 16% of its primary (Ds/Dp of <0.16±0.02),[6][a] which translates into a diameter of approximately 830 meters.[5] There are more than 100 binary asteroids known to exist in the asteroid belt.

Diameter and albedoEdit

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Shumarinaiko measures 5.253 kilometers in diameter and its surface has an albedo of 0.306,[7][8] while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 5.66 kilometers based on an absolute magnitude of 13.6.[3]


This minor planet was named after Lake Shumarinai. The lake is located within the Shumarinai Prefectural Natural Park in northern Hokkaidō, Japan. Artificially created to generate hydroelectricity in the 1940s, it is now known for its scenery.[2] The official naming citation was published by the Minor Planet Center on 15 December 2005 (M.P.C. 55722).[14]


  1. ^ a b c Brian D. Warner (2013) Lightcurve plot of 16525 Shumarinaiko, Palmer Divide Observatory: rotation period of 2.5932±0.0003 hours with a brightness amplitude of 0.08±0.01 mag. Quality code of 3. Secondary plot with an orbital period of 14.409±0.005 hours. Summary figures for (16525) Shumarinaiko at LCDB


  1. ^ a b c d "JPL Small-Body Database Browser: 16525 Shumarinaiko (1991 CU2)" (2017-07-05 last obs.). Jet Propulsion Laboratory. Retrieved 27 October 2017.
  2. ^ a b c Schmadel, Lutz D. (2006). "(16525) Shumarinaiko [2.40, 0.14, 2.4]". Dictionary of Minor Planet Names – (16525) Shumarinaiko, Addendum to Fifth Edition: 2003–2005. Springer Berlin Heidelberg. p. 101. doi:10.1007/978-3-540-34361-5_1054. ISBN 978-3-540-34361-5.
  3. ^ a b c d e f g h "LCDB Data for (16525) Shumarinaiko". Asteroid Lightcurve Database (LCDB). Retrieved 27 October 2017.
  4. ^ a b "Asteroid 16525 Shumarinaiko – Nesvorny HCM Asteroid Families V3.0". Small Bodies Data Ferret. Retrieved 27 October 2019.
  5. ^ a b Johnston, Robert (21 September 2014). "Asteroids with Satellites Database – (16525) Shumarinaiko". Johnston's Archive. Retrieved 27 October 2017.
  6. ^ a b c d Warner, Brian D.; Coley, Daniel (July 2013). "16525 Shumarinaiko: A New Nysa Binary". The Minor Planet Bulletin. 40 (3): 124–125. Bibcode:2013MPBu...40..124W. ISSN 1052-8091. Retrieved 27 October 2017.
  7. ^ 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 27 October 2017.
  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 Behrend, Raoul. "Asteroids and comets rotation curves – (16525) Shumarinaiko". Geneva Observatory. Retrieved 27 October 2017.
  10. ^ a b Higgins, David (January 2011). "Period Determination of Asteroid Targets Observed at Hunters Hill Observatory: May 2009 - September 2010". The Minor Planet Bulletin. 38 (1): 41–46. Bibcode:2011MPBu...38...41H. ISSN 1052-8091. Retrieved 27 October 2017.
  11. ^ Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results". Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 27 October 2017.
  12. ^ a b "16525 Shumarinaiko (1991 CU2)". Minor Planet Center. Retrieved 27 October 2017.
  13. ^ Nesvorný, D.; Broz, M.; Carruba, V. (December 2014). Identification and Dynamical Properties of Asteroid Families. Asteroids IV. pp. 297–321. arXiv:1502.01628. doi:10.2458/azu_uapress_9780816532131-ch016. ISBN 9780816532131.
  14. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 27 October 2017.

External linksEdit