Contents

896 Sphinx

896 Sphinx

Modelled shape of Sphinx from its lightcurve
Discovery [1]
Discovered by	M. F. Wolf
Discovery site	Heidelberg Obs.
Discovery date	1 August 1918
Designations
MPC designation	(896) Sphinx
Pronunciation	/ˈsfɪŋks/
Named after	Sphinx [2] (Greek/Egyptian mythology)
Alternative designations	A918 PE · 1918 DV
Minor planet category	main-belt [1][3] · (inner) background [4][5]
Adjectives	Sphinxian /ˈsfɪŋksiən/[6]
Orbital characteristics [3]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 0
Observation arc	101.50 yr (37,074 d)
Aphelion	2.6588 AU
Perihelion	1.9128 AU
Semi-major axis	2.2858 AU
Eccentricity	0.1632
Orbital period (sidereal)	3.46 yr (1,262 d)
Mean anomaly	211.73°
Mean motion	0° 17m 6.72s / day
Inclination	8.1903°
Longitude of ascending node	254.18°
Argument of perihelion	1.9628°
Physical characteristics
Mean diameter	11.974±0.071 km[7] 13.07±0.5 km[8] 14.45±0.35 km[9]
Synodic rotation period	21.038±0.008 h[10]
Pole ecliptic latitude	(172.0°, 20.0°) (λ1/β1)[5] (352.0°, 42.0°) (λ2/β2)[5]
Geometric albedo	0.163±0.009[9] 0.1971±0.017[8] 0.242±0.045[7]
Spectral type	n.a.
Absolute magnitude (H)	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[edit]

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[edit]

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 PlanetsbyPaul Herget in 1955 (H 87).^[2]

Physical characteristics[edit]

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[edit]

In June 2018, a rotational lightcurveofSphinx was obtained from photometric observations by Tom Polakis at the Command Module Observatory (V02) in Arizona. Lightcurve analysis gave a rotation periodof21.038±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[edit]

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[edit]

External links[edit]

• Lightcurve Database Query (LCDB), at www.minorplanet.info
• Dictionary of Minor Planet Names, Google books
• Asteroids and comets rotation curves, CdR – Geneva Observatory, Raoul Behrend
• Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
• 896 SphinxatAstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 896 Sphinx at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters