896 Sphinx
Modelled shape of Sphinx from its lightcurve
Discovery [1]
Discovered byM. F. Wolf
Discovery siteHeidelberg Obs.
Discovery date1 August 1918
Designations
(896) Sphinx
Pronunciation/ˈsfɪŋks/
Named after
A918 PE · 1918 DV
AdjectivesSphinxian /ˈsfɪŋksiən/[6]
Orbital characteristics [3]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 0
Observation arc101.50 yr (37,074 d)
Aphelion2.6588 AU
Perihelion1.9128 AU
2.2858 AU
Eccentricity0.1632
3.46 yr (1,262 d)
211.73°
0° 17m 6.72s / day
Inclination8.1903°
254.18°
1.9628°
Physical characteristics
Mean diameter
  • 11.974±0.071 km[7]
  • 13.07±0.5 km[8]
  • 14.45±0.35 km[9]
21.038±0.008 h[10]
  • (172.0°, 20.0°) (λ1/β1)[5]
  • (352.0°, 42.0°) (λ2/β2)[5]
  • 0.163±0.009[9]
  • 0.1971±0.017[8]
  • 0.242±0.045[7]
n.a.
11.6[1][3]

    896 Sphinx /ˈsfɪŋks/ is a background asteroid from the inner regions of the asteroid belt, that measures approximately 13 kilometers (8 miles) in diameter. It was discovered on 1 August 1918, by astronomer Max Wolf at the Heidelberg-Königstuhl State Observatory in southwest Germany.[1] The asteroid has a rotation period of 21.0 hours and is one of few low-numbered objects for which no spectral type has been determined. It was named after the Sphinx, a creature from Greek and Egyptian mythology.[2]

    Orbit and classification

    Sphinx is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.[4][5] It orbits the Sun in the inner asteroid belt at a distance of 1.9–2.7 AU once every 3 years and 6 months (1,262 days; semi-major axis of 2.29 AU). Its orbit has an eccentricity of 0.16 and an inclination of 8° with respect to the ecliptic.[3] The body's observation arc begins at Heidelberg Observatory on 9 October 1918, two months after its official discovery observation.[1]

    Naming

    This minor planet was named after the Sphinx, a legendary creature from Greek and Egyptian mythology. The female monster has the head of a woman, the haunches of a lion, and the wings of a bird. It has the habit of killing anyone who cannot answer her riddle. The naming citation was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 87).[2]

    Physical characteristics

    Contrary to most other low-numbered asteroids, no spectral type has been determined.[5][11] Based on its relatively high albedo (see below) and its location within the inner parts of the main-belt, Sphinx may possibly be a common, stony S-type asteroid.

    Rotation period

    In June 2018, a rotational lightcurve of Sphinx was obtained from photometric observations by Tom Polakis at the Command Module Observatory (V02) in Arizona. Lightcurve analysis gave a rotation period of 21.038±0.008 hours with a brightness variation of 0.16±0.02 magnitude (U=2+). However, an alternative period solution of 10.541±0.003 hours with an amplitude of 0.17±0.02 magnitude is also possible.[10] Both results supersede a tentative period determination by Laurent Bernasconi from September 2001 (U=1).[12]

    A modeled lightcurve using photometric data from the Lowell Photometric Database and from the Wide-field Infrared Survey Explorer (WISE) was published in 2018. It gave a divergent sidereal period of 12.95209±0.00002 hours and includes two spin axes at (172.0°, 20.0°) and (352.0°, 42.0°) in ecliptic coordinates (λ, β).[13]

    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, Sphinx measures (11.974±0.071), (13.07±0.5) and (14.45±0.35) kilometers in diameter and its surface has an albedo of (0.242±0.045), (0.1971±0.017) and (0.163±0.009), respectively.[7][8][9] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.2332 and a diameter of 13.17 kilometers based on an absolute magnitude of 11.6.[11] Alternative mean-diameter measurements published by the WISE team include (12.59±2.11 km), (13.320±0.122 km) and (13.658±3.101 km) with corresponding albedos of (0.25±0.11), (0.1924±0.0127) and (0.241±0.080).[5][11]

    References

    1. 1 2 3 4 5 "896 Sphinx (A918 PE)". Minor Planet Center. Retrieved 25 February 2020.
    2. 1 2 3 Schmadel, Lutz D. (2007). "(896) Sphinx". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 81. doi:10.1007/978-3-540-29925-7_897. ISBN 978-3-540-00238-3.
    3. 1 2 3 4 "JPL Small-Body Database Browser: 896 Sphinx (A918 PE)" (2020-02-01 last obs.). Jet Propulsion Laboratory. Retrieved 25 February 2020.
    4. 1 2 "Asteroid 896 Sphinx – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 25 February 2020.
    5. 1 2 3 4 5 6 "Asteroid 896 Sphinx". Small Bodies Data Ferret. Retrieved 25 February 2020.
    6. ↑ "Sphinx". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
    7. 1 2 3 Masiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; et al. (August 2014). "Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos". The Astrophysical Journal. 791 (2): 11. arXiv:1406.6645. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121.
    8. 1 2 3 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 25 February 2020.
    9. 1 2 3 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. (online, AcuA catalog p. 153)
    10. 1 2 Polakis, Tom (October 2018). "Lightcurve Analysis for Fourteen Main-belt Minor Planets" (PDF). Minor Planet Bulletin. 45 (4): 347–352. Bibcode:2018MPBu...45..347P. ISSN 1052-8091.
    11. 1 2 3 "LCDB Data for (896) Sphinx". Asteroid Lightcurve Database (LCDB). Retrieved 25 February 2020.
    12. ↑ Behrend, Raoul. "Asteroids and comets rotation curves – (896) Sphinx". Geneva Observatory. Retrieved 25 February 2020.
    13. ↑ 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. ISSN 0004-6361.
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