5176 Yoichi

5176 Yoichi, provisional designation 1989 AU, is a background asteroid from the central regions of the asteroid belt, approximately 17 kilometers (11 miles) in diameter. It was discovered on 4 January 1989, by Japanese astronomers Seiji Ueda and Hiroshi Kaneda at the Kushiro Observatory on Hokkaido, Japan.[1] The likely elongated asteroid has a brightness variation of 0.45 magnitude,[11] and occulted a star in the constellation Cetus in November 2014.[12] It was named for the Japanese town of Yoichi.[1]

5176 Yoichi
Discovery [1]
Discovered byS. Ueda
H. Kaneda
Discovery siteKushiro Obs.
Discovery date4 January 1989
Designations
(5176) Yoichi
Named after
Yoichi [1] (Japanese town)
1989 AU · 1935 YH
1948 VS · 1948 WS
1952 OH1 · 1961 TK1
main-belt [1][2] · (middle)
background [3]
Orbital characteristics [2]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc81.52 yr (29,777 d)
Aphelion3.5198 AU
Perihelion1.8546 AU
2.6872 AU
Eccentricity0.3098
4.41 yr (1,609 d)
295.85°
0° 13m 25.32s / day
Inclination7.7043°
93.615°
269.81°
Physical characteristics
Mean diameter
15.68±1.57 km[4]
16.54 km (derived)[5]
16.56±0.7 km[6]
16.74±4.79 km[7]
18.92±5.20 km[8]
19.49±1.15 km[9]
0.05±0.03[7]
0.054±0.048[8]
0.06±0.03[4]
0.061±0.008[9]
0.0777 (derived)[5]
0.0849±0.007[6]
S (assumed)[5]
12.20[7][9]
12.3[2][5]
12.36±0.26[10]
12.40[8]
12.57[4]

    Orbit and classification

    Yoichi is a non-family asteroid from the main belt's background population.[3] It orbits the Sun in the central main-belt at a distance of 1.9–3.5 AU once every 4 years and 5 months (1,609 days; semi-major axis of 2.69 AU). Its orbit has an eccentricity of 0.31 and an inclination of 8° with respect to the ecliptic.[2]

    The body's observation arc begins with its first observations as 1935 YH at Johannesburg Observatory in December 1935, or 53 years prior to its official discovery observation at Kushiro.[1]

    Physical characteristics

    Yoichi is an assumed S-type asteroid, while the body's albedo is rather indicative of a carbonaceous C-type asteroid (see below).[5]

    Rotation period

    In November 2015, photometric data of Yoichi was taken by astronomers at the Oakley Southern Sky Observatory in Australia. However no rotational lightcurve could be constructed. The asteroid's brightness amplitude was 0.42 magnitude (U=n.a.), indicative for an elongated shape.[11] As of 2018, the body's rotation period, pole and shape remain unknown.[5]

    Diameter and albedo

    According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Yoichi measures between 15.68 and 19.49 kilometers in diameter and its surface has an albedo between 0.05 and 0.0849.[4][6][7][8][9]

    The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0777 and a diameter of 16.54 kilometers based on an absolute magnitude of 12.3.[5]

    Occultation

    On 2 November 2014, Yoichi occulted 8.4 magnitude star HIP 14421 in the constellation Cetus, causing a magnitude drop from 8.4 to 14.1 during 2.8 seconds. The occultation was visible over Southern Japan, Eastern China, as well as from Southern California to North Florida. The asteroid's 23-kilometer-wide shadow had a speed of approximately 6.8 km/s. An approximate diameter of 20 kilometers was assumed for the asteroid.[12]

    Naming

    This minor planet was named after the Japanese town of Yoichi on Hokkaido, where the discovering Kushiro Observatory is located.[1] The official naming citation was published by the Minor Planet Center on 4 August 2001 (M.P.C. 43189).[13]

    References
    1. "5176 Yoichi (1989 AU)". Minor Planet Center. Retrieved 25 April 2018.
    2. "JPL Small-Body Database Browser: 5176 Yoichi (1989 AU)" (2017-07-05 last obs.). Jet Propulsion Laboratory. Retrieved 25 April 2018.
    3. "Asteroid 5176 Yoichi – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 29 October 2019.
    4. Nugent, C. R.; Mainzer, A.; Bauer, J.; Cutri, R. M.; Kramer, E. A.; Grav, T.; et al. (September 2016). "NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos". The Astronomical Journal. 152 (3): 12. arXiv:1606.08923. Bibcode:2016AJ....152...63N. doi:10.3847/0004-6256/152/3/63.
    5. "LCDB Data for (5176) Yoichi". Asteroid Lightcurve Database (LCDB). Retrieved 25 April 2018.
    6. 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.
    7. 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". The Astrophysical Journal. 814 (2): 13. arXiv:1509.02522. Bibcode:2015ApJ...814..117N. doi:10.1088/0004-637X/814/2/117.
    8. 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.
    9. 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 17 October 2019. (online, AcuA catalog p. 153)
    10. 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.
    11. Hess, Kylie; Ditteon, Richard (April 2016). "Asteroid Lightcurve Analysis at the Oakley Southern Sky Observatory: 2014 November". The Minor Planet Bulletin. 43 (2): 120. Bibcode:2016MPBu...43..120H. ISSN 1052-8091.
    12. Preston, Steve. "(5176) Yoichi / HIP 14421 event on 2014 Nov 02, 10:58 UT". asteroidoccultation.com. Retrieved 25 April 2018. (Summary)
    13. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 25 April 2018.

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