251 Sophia

251 Sophia is a stony background asteroid from the outer regions of the asteroid belt. It was discovered on 4 October 1885, by astronomer Johann Palisa at the Vienna Observatory in Austria.[1] The S-type asteroid (S/L) has a rotation period of 20.2 hours and measures approximately 28 kilometers (17 miles) in diameter. It was named after Sophia von Seeliger, wife of German astronomer Hugo von Seeliger (1849–1924).[3]

251 Sophia
Modelled shape of Sophia from its lightcurve
Discovery [1]
Discovered byJ. Palisa
Discovery siteVienna Obs.
Discovery date4 October 1885
Designations
(251) Sophia
PronunciationGerman: [zoːˈfiːaː][2]
Named after
1950 RH1 · 1953 FN1
A907 UA
Orbital characteristics [4]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 0
Observation arc134.29 yr (49,050 d)
Aphelion3.4015 AU
Perihelion2.8035 AU
3.1025 AU
Eccentricity0.0964
5.46 yr (1,996 d)
192.53°
0° 10m 49.44s / day
Inclination10.511°
156.02°
286.51°
Physical characteristics
Mean diameter
  • 27.495±0.197 km[7]
  • 28.42±4.5 km[8]
  • 29.65±0.42 km[9]
20.216±0.008 h[10]
  • (235.0°, −52.0°) (λ1/β1)[11]
  • (47.0°, 84.0°) (λ2/β2)[11]
  • 0.207±0.007[9]
  • 0.2188±0.091[8]
  • 0.234±0.042[7]
9.9[1][4]

    Orbit and classification

    Sophia is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.[5][6] It orbits the Sun in the outer asteroid belt at a distance of 2.8–3.4 AU once every 5 years and 6 months (1,996 days; semi-major axis of 3.1 AU). Its orbit has an eccentricity of 0.10 and an inclination of 11° with respect to the ecliptic.[4] The body's observation arc begins at Vienna Observatory with its official discovery observation on 4 October 1885.[1]

    Naming

    This minor planet was named after Sophia von Seeliger (née Stoeltzel), wife of German astronomer Hugo von Seeliger (1849–1924) on the occasion of their marriage (A. Schnell). The naming likely took place in 1885, on the meeting of the Astronomische Gesellschaft in Geneva, Switzerland. Seeliger, who proposed the name to the discoverer, was later honored with asteroid 892 Seeligeria, discovered by Max Wolf in 1918.[3]

    Physical characteristics

    In the Tholen-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2), Sophia is a common, stony S-type asteroid, while in the survey's Bus–Binzel (SMASS) taxonomic variant, it is an Sl-subtype, which transitions from the S-type to the uncommon L-type.[6][12] In the SDSS-based taxonomy, it is an L-type asteroid[13]

    Rotation period and poles

    In December 2000, a rotational lightcurve of Sophia was obtained from photometric observations by Bill Holliday in New Braunfels, Texas. Lightcurve analysis gave a well-defined rotation period of 20.216±0.008 hours with a brightness variation of 0.30±0.02 magnitude (U=3).[10] Between 2005 and 2013, additional observations by French amateur astronomers Laurent Bernasconi, Etienne Morelle and René Roy gave a tentative period of 20.28 hours with an amplitude between 0.25 and 0.61 (U=2/2/2).[14]

    Modeled lightcurves by Josef Ďurech and Josef Hanuš, using photometric data including from the Lowell Photometric Database and from the Wide-field Infrared Survey Explorer (WISE) were published in 2018. It gave a concurring sidereal period of 20.2221±0.0002 and 20.2222±0.0001 hours, respectively. Hanuš also gave two spin axes at (235.0°, −52.0°) and (47.0°, 84.0°) in ecliptic coordinates (λ, β).[15][16][11]

    Diameter and albedo

    According to the surveys carried out by the NEOWISE mission of NASA's WISE telescope, the Infrared Astronomical Satellite IRAS, and the Japanese Akari satellite, Sophia measures (27.495±0.197), (28.42±4.5) and (29.65±0.42) kilometers in diameter and its surface has an albedo of (0.234±0.042), (0.2188±0.091) and (0.207±0.007), respectively.[7][8][9] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.2377 and a diameter of 28.54 kilometers based on an absolute magnitude of 9.9.[11] Alternative mean-diameter measurements published by the WISE team include (28.201±1.301 km) and (28.804±0.212 km) with corresponding albedos of (0.244±0.047) and (0.2205±0.0481).[6][11]

    References
    1. "251 Sophia". Minor Planet Center. Retrieved 14 March 2020.
    2. (German Names)
    3. Schmadel, Lutz D. (2007). "(251) Sophia". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 37. doi:10.1007/978-3-540-29925-7_252. ISBN 978-3-540-00238-3.
    4. "JPL Small-Body Database Browser: 251 Sophia" (2020-01-20 last obs.). Jet Propulsion Laboratory. Retrieved 14 March 2020.
    5. "Asteroid 251 Sophia – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 14 March 2020.
    6. "Asteroid 251 Sophia". Small Bodies Data Ferret. Retrieved 14 March 2020.
    7. Mainzer, A. K.; Bauer, J. M.; Cutri, R. M.; Grav, T.; Kramer, E. A.; Masiero, J. R.; et al. (June 2016). "NEOWISE Diameters and Albedos V1.0". NASA Planetary Data System. Bibcode:2016PDSS..247.....M. Retrieved 14 March 2020.
    8. 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 14 March 2020.
    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 14 March 2020. (online, AcuA catalog p. 153)
    10. Holliday, Bill (June 2001). "Photometry of Asteroid 251 Sophia, 393 Lampetia, and (20898) 2000 WE147, September 2000 through January 2001" (PDF). Minor Planet Bulletin. 28 (2): 26–28. Bibcode:2001MPBu...28...26H.
    11. "LCDB Data for (251) Sophia". Asteroid Lightcurve Database (LCDB). Retrieved 14 March 2020.
    12. Lazzaro, D.; Angeli, C. A.; Carvano, J. M.; Mothé-Diniz, T.; Duffard, R.; Florczak, M. (November 2004). "S3OS2: the visible spectroscopic survey of 820 asteroids" (PDF). Icarus. 172 (1): 179–220. Bibcode:2004Icar..172..179L. doi:10.1016/j.icarus.2004.06.006. Retrieved 14 March 2020.
    13. Carvano, J. M.; Hasselmann, P. H.; Lazzaro, D.; Mothé-Diniz, T. (February 2010). "SDSS-based taxonomic classification and orbital distribution of main belt asteroids". Astronomy and Astrophysics. 510: 12. Bibcode:2010A&A...510A..43C. doi:10.1051/0004-6361/200913322. Retrieved 14 March 2020. (PDS data set)
    14. Behrend, Raoul. "Asteroids and comets rotation curves – (251) Sophia". Geneva Observatory. Retrieved 14 March 2020.
    15. Ďurech, J.; Hanuš, J.; Alí-Lagoa, V. (September 2018). "Asteroid models reconstructed from the Lowell Photometric Database and WISE data". Astronomy and Astrophysics. 617: A57. arXiv:1807.02083. Bibcode:2018A&A...617A..57D. doi:10.1051/0004-6361/201833437. ISSN 0004-6361.
    16. Hanus, J.; Delbo', M.; Alí-Lagoa, V.; Bolin, B.; Jedicke, R.; Durech, J.; et al. (January 2018). "Spin states of asteroids in the Eos collisional family". Icarus. 299: 84–96. arXiv:1707.05507. Bibcode:2018Icar..299...84H. doi:10.1016/j.icarus.2017.07.007. ISSN 0019-1035.
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