7187 Isobe

7187 Isobe, provisional designation 1992 BW, is a likely binary Hungaria asteroid from the inner regions of the asteroid belt, approximately 5 kilometers in diameter. It was discovered on 30 January 1992, by American astronomer Eleanor Helin at Palomar Observatory in California, United States.[3] It is named after Japanese astronomer Syuzo Isobe.[2]

7187 Isobe
Discovery [1]
Discovered byE. F. Helin
Discovery sitePalomar Obs.
Discovery date30 January 1992
Designations
(7187) Isobe
Named after
Syuzo Isobe
(Japanese astronomer)[2]
1992 BW · 1985 QC3
main-belt · (inner) [1]
Hungaria [3][4]
Orbital characteristics [1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc30.61 yr (11,182 days)
Aphelion2.1048 AU
Perihelion1.7700 AU
1.9374 AU
Eccentricity0.0864
2.70 yr (985 days)
251.94°
0° 21m 55.8s / day
Inclination21.784°
315.32°
86.408°
Known satellites1 (likely)[4][5]
Physical characteristics
Dimensions3.85 km (calculated)[4]
4.85±1.43 km[6]
5.421±1.086 km[7]
6.05±1.46 km[8]
2.440±0.002 h[9]
2.58±0.01 h[10]
4.241±0.006 h[11]
4.2427±0.002 h[5]
4.2432±0.0005 h[12]
0.093±0.027[13]
0.12±0.09[6]
0.134±0.104[8]
0.167±0.094[7]
0.3 (assumed)[4]
E [4]
13.89[8] · 13.90[7] · 14.0[1][4] · 14.50[6]

    Classification and orbit

    The presumed E-type asteroid is a member of the Hungaria family, which form the innermost dense concentration of asteroids in the Solar System.[3][4] Isobe orbits the Sun in the inner main-belt at a distance of 1.8–2.1 AU once every 2 years and 8 months (985 days). Its orbit has an eccentricity of 0.09 and an inclination of 22° with respect to the ecliptic.[1] It was first identified as 1985 QC3 at the discovery observatory in 1985, extending the body's observation arc by 7 years prior to its official discovery observation.[3]

    According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Isobe measures between 4.85 and 6.05 kilometers in diameter, and its surface has an albedo between 0.12 and 0.167.[6][7][8] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.30 – a compromise value between 0.4 and 0.2, corresponding to the Hungaria asteroids both as family and orbital group – and calculates a diameter of 3.85 kilometers with an absolute magnitude of 14.0.[4]

    Moon and lightcurve

    Since August 2004, American astronomer Brian Warner obtained several rotational lightcurves of Isobe at his Palmer Divide Observatory in Colorado. Light curve and follow-up analysis gave a well-defined rotation period of 4.2432 hours with a brightness amplitude of 0.22 magnitude (U=3), after initial photometric observations indicated a shorter period solution of 2.4 hours.[5]

    In 2012, observations by Brian Warner also indicated that Isobe is very likely a synchronous binary asteroid, orbited by a minor-planet moon every 33 hours. The size of this satellite remains unknown and no secondary-to-primary diameter ratio has been published. Isobe's binary nature still needs further observations.

    Isobe was also observed by American astronomer Robert Stephens at the Center for Solar System Studies in September 2015, giving a period of 4.241 hours with an amplitude of 0.22 magnitude. However, no mutual occulation events have been found during the two-night long observation period (U=3-).[11]

    Naming

    The asteroid has been named after Syuzo Isobe (born 1942), a Japanese scientist at NAOJ, individual member of the IAU, and president of the Japan Spaceguard Association. He significantly contributed in establishing the Bisei Spaceguard Center, an observatory designed for the observation of NEOs and earth-orbiting space debris.[2][14] The approved naming citation was published by the Minor Planet Center on 1 November 2001 (M.P.C. 43762).[15]

    References
    1. "JPL Small-Body Database Browser: 7187 Isobe (1992 BW)" (2016-04-01 last obs.). Jet Propulsion Laboratory. Retrieved 4 July 2017.
    2. Schmadel, Lutz D. (2007). "(7187) Isobe". Dictionary of Minor Planet Names – (7187) Isobe. Springer Berlin Heidelberg. p. 581. doi:10.1007/978-3-540-29925-7_6338. ISBN 978-3-540-00238-3.
    3. "7187 Isobe (1992 BW)". Minor Planet Center. Retrieved 10 March 2017.
    4. "LCDB Data for (7187) Isobe". Asteroid Lightcurve Database (LCDB). Retrieved 10 March 2017.
    5. Warner, Brian D. (January 2013). "Rounding Up the Unusual Suspects". The Minor Planet Bulletin. 40 (1): 36–42. Bibcode:2013MPBu...40...36W. ISSN 1052-8091. Retrieved 10 March 2017.
    6. 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. Retrieved 10 March 2017.
    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. Retrieved 10 March 2017.
    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. Retrieved 10 March 2017.
    9. Warner, Brian D. (March 2005). "Lightcurve analysis for asteroids 242, 893, 921, 1373, 1853, 2120, 2448 3022, 6490, 6517, 7187, 7757, and 18108". The Minor Planet Bulletin. 32 (1): 4–7. Bibcode:2005MPBu...32....4W. ISSN 1052-8091. Retrieved 10 March 2017.
    10. Warner, Brian D. (June 2008). "Asteroid Lightcurve Analysis at the Palmer Divide Observatory: September-December 2007". The Minor Planet Bulletin. 35 (2): 67–71. Bibcode:2008MPBu...35...67W. ISSN 1052-8091. Retrieved 10 March 2017.
    11. Stephens, Robert D. (January 2016). "Asteroids Observed from CS3: 2015 July - September". The Minor Planet Bulletin. 43 (1): 52–56. Bibcode:2016MPBu...43...52S. ISSN 1052-8091. Retrieved 10 March 2017.
    12. Warner, Brian D. (July 2011). "Asteroid Lightcurve Analysis at the Palmer Divide Observatory: 2010 December- 2011 March". The Minor Planet Bulletin. 38 (3): 142–149. Bibcode:2011MPBu...38..142W. ISSN 1052-8091. Retrieved 10 March 2017.
    13. Gil-Hutton, R.; Lazzaro, D.; Benavidez, P. (June 2007). "Polarimetric observations of Hungaria asteroids". Astronomy and Astrophysics. 468 (3): 1109–1114. Bibcode:2007A&A...468.1109G. doi:10.1051/0004-6361:20077178. Retrieved 10 March 2017.
    14. "Syuzo ISOBE". IAU – International Astronomical Union. Retrieved 8 October 2015.
    15. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 10 March 2017.

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