896 Sphinx
{{Short description|Main-belt asteroid}}
{{Use dmy dates|date=February 2020}}
{{Infobox planet
| minorplanet = yes
| name = 896 Sphinx
| background = #D6D6D6
| image = 000896-asteroid shape model (896) Sphinx.png
| image_scale =
| caption = Modelled shape of Sphinx from its lightcurve
| discoverer = M. F. Wolf
| discovery_site = Heidelberg Obs.
| discovered = 1 August 1918
| mpc_name = (896) Sphinx
| pronounced = {{IPAc-en|'|s|f|ɪ|ŋ|k|s}}
| alt_names = A918 PE{{·}}1918 DV
| named_after = {{plainlist|
| mp_category = {{plainlist|
- main-belt{{·}}{{small|(inner)}}
- background}}
| adjective = Sphinxian {{IPAc-en|'|s|f|ɪ|ŋ|k|s|i|ə|n}}{{OED|Sphinx}}
| epoch = 31 May 2020 (JD 2459000.5)
| uncertainty = 0
| observation_arc = 101.50 yr (37,074 d)
| aphelion = 2.6588 AU
| perihelion = 1.9128 AU
| semimajor = 2.2858 AU
| eccentricity = 0.1632
| period = 3.46 yr (1,262 d)
| mean_anomaly = 211.73°
| mean_motion = {{Deg2DMS|0.2852|sup=ms}} / day
| inclination = 8.1903°
| asc_node = 254.18°
| arg_peri = 1.9628°
| mean_diameter = {{plainlist|
| rotation = {{val|21.038|0.008|ul=h}}
| pole_ecliptic_lat={{plainlist|
| albedo = {{plainlist|
| spectral_type = n.a.
}}
896 Sphinx {{IPAc-en|'|s|f|ɪ|ŋ|k|s}} is a background asteroid from the inner regions of the asteroid belt, that measures approximately {{convert|13|km|mi|abbr=off|sigfig=1|sp=us}} 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 {{MoMP|896|naming citation}} was mentioned in The Names of the Minor Planets by Paul Herget in 1955 ({{small|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 {{Obscode|V02}} in Arizona. Lightcurve analysis gave a rotation period of {{val|21.038|0.008}} hours with a brightness variation of {{val|0.16|0.02}} magnitude ({{small|U=2+}}). However, an alternative period solution of {{val|10.541|0.003}} hours with an amplitude of {{val|0.17|0.02}} magnitude is also possible. Both results supersede a tentative period determination by Laurent Bernasconi from September 2001 ({{small|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 {{val|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).
= 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 ({{val|11.974|0.071}}), ({{val|13.07|0.5}}) and ({{val|14.45|0.35}}) kilometers in diameter and its surface has an albedo of ({{val|0.242|0.045}}), ({{val|0.1971|0.017}}) and ({{val|0.163|0.009}}), 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 ({{val|12.59|2.11|u=km}}), ({{val|13.320|0.122|u=km}}) and ({{val|13.658|3.101|u=km}}) with corresponding albedos of ({{val|0.25|0.11}}), ({{val|0.1924|0.0127}}) and ({{val|0.241|0.080}}).
References
{{reflist|30em|refs=
|type = 2020-02-01 last obs.
|title = JPL Small-Body Database Browser: 896 Sphinx (A918 PE)
|url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2000896
|publisher = Jet Propulsion Laboratory
|access-date = 25 February 2020}}
|title = Dictionary of Minor Planet Names
|last = Schmadel | first = Lutz D.
|publisher = Springer Berlin Heidelberg
|chapter = (896) Sphinx
|page = 81
|date = 2007
|doi = 10.1007/978-3-540-29925-7_897
|isbn = 978-3-540-00238-3}}
|title = 896 Sphinx (A918 PE)
|work = Minor Planet Center
|url = https://www.minorplanetcenter.net/db_search/show_object?object_id=896
|access-date = 25 February 2020}}
|title = Asteroids and comets rotation curves – (896) Sphinx
|last = Behrend |first = Raoul
|publisher = Geneva Observatory
|url = http://obswww.unige.ch/~behrend/page3cou.html#000896
|access-date = 25 February 2020}}
|display-authors = 6
|first1 = Joseph R. |last1 = Masiero
|first2 = T. |last2 = Grav
|first3 = A. K. |last3 = Mainzer
|first4 = C. R. |last4 = Nugent
|first5 = J. M. |last5 = Bauer
|first6 = R. |last6 = Stevenson
|first7 = S. |last7 = Sonnett
|date = August 2014
|title = Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos
|journal = The Astrophysical Journal
|volume = 791
|issue = 2
|page = 11
|bibcode = 2014ApJ...791..121M
|doi = 10.1088/0004-637X/791/2/121
|arxiv = 1406.6645}}
|display-authors = 6
|first1 = Fumihiko |last1 = Usui
|first2 = Daisuke |last2 = Kuroda
|first3 = Thomas G. |last3 = Müller
|first4 = Sunao |last4 = Hasegawa
|first5 = Masateru |last5 = Ishiguro
|first6 = Takafumi |last6 = Ootsubo
|first7 = Daisuke |last7 = Ishihara
|first8 = Hirokazu |last8 = Kataza
|first9 = Satoshi |last9 = Takita
|first10 = Shinki |last10 = Oyabu
|first11 = Munetaka |last11 = Ueno
|first12 = Hideo |last12 = Matsuhara
|first13 = Takashi |last13 = Onaka
|date = October 2011
|title = Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey
|journal = Publications of the Astronomical Society of Japan
|volume = 63
|issue = 5
|pages = 1117–1138
|bibcode = 2011PASJ...63.1117U
|doi = 10.1093/pasj/63.5.1117
|doi-access=
}} ([http://vizier.cfa.harvard.edu/viz-bin/VizieR-5?-source=J/PASJ/63/1117/acua_v1&Num=896 online], [https://core.ac.uk/download/pdf/43545172.pdf AcuA catalog p. 153])
|first1 = E. F. |last1 = Tedesco
|first2 = P. V. |last2 = Noah
|first3 = M. |last3 = Noah
|first4 = S. D. |last4 = Price
|date = October 2004
|title = IRAS Minor Planet Survey V6.0
|url = https://sbnarchive.psi.edu/pds3/iras/IRAS_A_FPA_3_RDR_IMPS_V6_0/data/diamalb.tab
|journal = NASA Planetary Data System
|volume = 12
|pages = IRAS-A-FPA-3-RDR-IMPS-V6.0
|bibcode = 2004PDSS...12.....T
|access-date = 25 February 2020}}
|title = LCDB Data for (896) Sphinx
|publisher = Asteroid Lightcurve Database (LCDB)
|url = http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=896
|access-date = 25 February 2020}}
|last1 = Polakis |first1 = Tom
|date = October 2018
|title = Lightcurve Analysis for Fourteen Main-belt Minor Planets
|journal = Minor Planet Bulletin
|url = http://www.minorplanet.info/MPB/issues/MPB_45-4.pdf
|volume = 45
|issue = 4
|pages = 347–352
|bibcode = 2018MPBu...45..347P
|issn = 1052-8091}}
|last1 = Ďurech |first1 = J.
|last2 = Hanuš |first2 = J.
|last3 = Alí-Lagoa |first3 = V.
|date = September 2018
|title = Asteroid models reconstructed from the Lowell Photometric Database and WISE data
|journal = Astronomy and Astrophysics
|volume = 617
|page = A57
|bibcode = 2018A&A...617A..57D
|issn = 0004-6361
|arxiv = 1807.02083}}
|title = Asteroid 896 Sphinx
|work = Small Bodies Data Ferret
|url = https://sbntools.psi.edu/ferret/SimpleSearch/results.action?targetName=896+Sphinx
|access-date = 25 February 2020}}
|title = Asteroid 896 Sphinx – Proper Elements
|publisher = AstDyS-2, Asteroids – Dynamic Site
|url = https://newton.spacedys.com/astdys/index.php?pc=1.1.6&n=896
|access-date= 25 February 2020}}
}}
External links
- [http://www.minorplanet.info/PHP/OneAsteroidInfo.php Lightcurve Database Query] (LCDB), at www.minorplanet.info
- [https://books.google.com/books?id=aeAg1X7afOoC&pg Dictionary of Minor Planet Names], Google books
- [http://obswww.unige.ch/~behrend/page_cou.html Asteroids and comets rotation curves, CdR] – Geneva Observatory, Raoul Behrend
- [http://www.minorplanetcenter.net/iau/lists/NumberedMPs000001.html Discovery Circumstances: Numbered Minor Planets (1)-(5000)] – Minor Planet Center
- {{AstDys|896}}
- {{JPL small body}}
{{Minor planets navigator |895 Helio |number=896 |897 Lysistrata}}
{{Small Solar System bodies}}
{{Authority control}}
{{DEFAULTSORT:Sphinx}}