896 Sphinx

896 Sphinx Template:IPAc-en is a background asteroid from the inner regions of the asteroid belt, that measures approximately Template:Convert in diameter. It was discovered on 1 August 1918, by astronomer Max Wolf at the Heidelberg-Königstuhl State Observatory in southwest Germany. 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.

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. 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. The body's observation arc begins at Heidelberg Observatory on 9 October 1918, two months after its official discovery observation.

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 Template:MoMP was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 87).

Physical characteristics

Contrary to most other low-numbered asteroids, no spectral type has been determined. 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 Template:Obscode in Arizona. Lightcurve analysis gave a rotation period of Template:Val hours with a brightness variation of Template:Val magnitude (U=2+). However, an alternative period solution of Template:Val hours with an amplitude of Template:Val magnitude is also possible. Both results supersede a tentative period determination by Laurent Bernasconi from September 2001 (U=1).

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 Template:Val hours and includes two spin axes at (172.0°, 20.0°) and (352.0°, 42.0°) in ecliptic coordinates (λ, β).

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 (Template:Val), (Template:Val) and (Template:Val) kilometers in diameter and its surface has an albedo of (Template:Val), (Template:Val) and (Template:Val), respectively. 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. Alternative mean diameter measurements published by the WISE team include (Template:Val), (Template:Val) and (Template:Val) with corresponding albedos of (Template:Val), (Template:Val) and (Template:Val).

External links

• 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
• Template:AstDys
• Template:JPL small body