15415 Rika

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15415 Rika
Discovery [1]
Discovered by A. Nakamura
Discovery site Kuma Kogen Obs.
Discovery date 4 February 1998
MPC designation (15415) Rika
Named after
Rika Akana (character in the drama Tokyo Love Story)[1]
1998 CA1 · 1983 PC1
1983 PH · 1997 WK22
main-belt[1][2] · (inner)
background[3] · Flora[4]
Orbital characteristics[2]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc 63.41 yr (23,161 d)
Aphelion 2.7047 AU
Perihelion 1.6979 AU
2.2013 AU
Eccentricity 0.2287
3.27 yr (1,193 d)
0° 18m 6.48s / day
Inclination 7.4787°
Physical characteristics
Mean diameter
2.830±0.488 km[5]
3.74 km (calculated)[4]
6.3636±0.0008 h[6][a]
0.24 (assumed)[4]
S (assumed)[4]

15415 Rika, provisional designation 1998 CA1, is a bright background asteroid from the Florian region of the inner asteroid belt, approximately 3 kilometers (2 miles) in diameter. It was discovered on 4 February 1998, by Japanese astronomer Akimasa Nakamura at the Kuma Kogen Astronomical Observatory in southern Japan.[1] The presumed S-type asteroid has a rotation period of 6.36 hours and possibly an elongated shape.[4] It was named after Rika Akana, a character in the Japanese film and later television adapted drama Tokyo Love Story.[1]

Orbit and classification[edit]

Rika is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.[3] 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.[4]

It orbits the Sun in the inner asteroid belt at a distance of 1.7–2.7 AU once every 3 years and 3 months (1,193 days; semi-major axis of 2.2 AU). Its orbit has an eccentricity of 0.23 and an inclination of 7° with respect to the ecliptic.[2]

The body's observation arc begins with a precovery published by the Digitized Sky Survey and taken at the Palomar Observatory in November 1954, more than 43 years prior to its official discovery observation at Kuma Kogen.[1]

Physical characteristics[edit]

Rika is an assumed, common S-type asteroid,[4] despite the exceptionally high albedo (see below) measured by the Wide-field Infrared Survey Explorer (WISE).

Rotation period[edit]

In October 2006, a rotational lightcurve of Rika was obtained from photometric observations by astronomers at the Skalnaté pleso Observatory in Slovakia. Lightcurve analysis gave a well-defined rotation period of 6.3636 hours with a high brightness amplitude of 1.06 magnitude, indicating that the body has an elongated shape (U=3).[6][a]

Diameter and albedo[edit]

According to the survey carried out by the NEOWISE mission of NASA's WISE telescope, Rika measures 2.830 kilometers in diameter and its surface has a high albedo of 0.6053.[5] 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 3.74 kilometers based on an absolute magnitude of 14.3.[4]


This minor planet was named after Rika Akana, the heroine played by Honami Suzuki in the manga-based Japanese television drama Tokyo Love Story. Some episodes of the dorama were filmed on locations near the town of Kumakōgen, where the discovering observatory of this asteroid is located.[1]

The official naming citation was published by the Minor Planet Center on 13 October 2000 (M.P.C. 41388).[8]


  1. ^ a b Pravec (2006) Lightcurve plot of (15415) Rika by Husárik and Kusnirák, from Ondrejov data published by the NEO Photometric Program and collaborating projects: rotation period 6.3632±0.0007 hours (basically identical with 6.3636±0.0008 h) and a brightness amplitude of 1.06 mag. Quality code is 3. Summary figures at the LCDB.


  1. ^ a b c d e f g h "15415 Rika (1998 CA1)". Minor Planet Center. Retrieved 28 May 2018. 
  2. ^ a b c d "JPL Small-Body Database Browser: 15415 Rika (1998 CA1)" (2018-04-24 last obs.). Jet Propulsion Laboratory. Retrieved 28 May 2018. 
  3. ^ a b "Asteroid 15415 Rika". Small Bodies Data Ferret. Retrieved 28 May 2018. 
  4. ^ a b c d e f g h i "LCDB Data for (15415) Rika". Asteroid Lightcurve Database (LCDB). Retrieved 28 May 2018. 
  5. ^ a b c d Masiero, Joseph R.; Nugent, C.; Mainzer, A. K.; Wright, E. L.; Bauer, J. M.; Cutri, R. M.; et al. (October 2017). "NEOWISE Reactivation Mission Year Three: Asteroid Diameters and Albedos" (PDF). The Astronomical Journal. 154 (4): 10. arXiv:1708.09504Freely accessible. Bibcode:2017AJ....154..168M. doi:10.3847/1538-3881/aa89ec. Retrieved 28 May 2018. 
  6. ^ a b Husárik, M.; Kusnirák, P. (February 2008). "Relative photometry of numbered asteroids (1314), (2257), (3541), (4080), (4155), (12081) and (15415)". Contributions of the Astronomical Observatory Skalnaté Pleso: 47–60. Bibcode:2008CoSka..38...47H. 
  7. ^ 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" (PDF). Icarus. 261: 34–47. arXiv:1506.00762Freely accessible. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 28 May 2018. 
  8. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 28 May 2018. 

External links[edit]