896 Sphinx

Main-belt asteroid

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 Planets by Paul 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 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

[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]

1. ^ a b c d e "896 Sphinx (A918 PE)". Minor Planet Center. Retrieved 25 February 2020.
2. ^ a b c 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. ^ a b c d "JPL Small-Body Database Browser: 896 Sphinx (A918 PE)" (2020-02-01 last obs.). Jet Propulsion Laboratory. Retrieved 25 February 2020.
4. ^ a b "Asteroid 896 Sphinx – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 25 February 2020.
5. ^ a b c d e f "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. ^ a b c 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. ^ a b c 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. ^ a b c 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/63.5.1117.1117-1138&rft.date=2011-10&rft_id=info:doi/10.1093/pasj/63.5.1117&rft_id=info:bibcode/2011PASJ...63.1117U&rft.aulast=Usui&rft.aufirst=Fumihiko&rft.au=Kuroda,+Daisuke&rft.au=Müller,+Thomas+G.&rft.au=Hasegawa,+Sunao&rft.au=Ishiguro,+Masateru&rft.au=Ootsubo,+Takafumi&rft.au=Ishihara,+Daisuke&rft.au=Kataza,+Hirokazu&rft.au=Takita,+Satoshi&rft.au=Oyabu,+Shinki&rft.au=Ueno,+Munetaka&rft.au=Matsuhara,+Hideo&rft.au=Onaka,+Takashi&rfr_id=info:sid/en.wikipedia.org:896+Sphinx" class="Z3988"> (online, AcuA catalog p. 153)
10. ^ a b 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 1052-8091.347-352&rft.date=2018-10&rft.issn=1052-8091&rft_id=info:bibcode/2018MPBu...45..347P&rft.aulast=Polakis&rft.aufirst=Tom&rft_id=http://www.minorplanet.info/MPB/issues/MPB_45-4.pdf&rfr_id=info:sid/en.wikipedia.org:896+Sphinx" class="Z3988">
11. ^ a b c "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.

## 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 Sphinx at AstDyS-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 viewer * Orbit parameters * Physical parameters

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