View source for Astronomy:65489 Ceto

{{Short description|Minor planet}}
{{Infobox planet 
| minorplanet = yes
| background = #C2E0FF
| name = 65489 Ceto
| pronounced = {{IPAc-en|ˈ|s|iː|t|oʊ}}
| adjectives = Cetoan {{IPAc-en|s|iː|ˈ|t|oʊ|ə|n}} or Cetoian {{IPAc-en|s|iː|ˈ|t|oʊ|.|i|ə|n}}
| image = ceto-phorcys hst.jpg
| image_scale =
| caption = [[Astronomy:Hubble Space Telescope|Hubble Space Telescope]] image of Ceto and Phorcys, taken in 2006
| discovery_ref = 
| discoverer = C. A. Trujillo and [[Biography:Michael E. Brown|M. Brown]]
| discovery_site = [[Organization:Palomar Observatory|Palomar]]
| discovered = 22 March 2003
| mpc_name = (65489) Ceto
| alt_names = {{mp|2003 FX|128}}
| named_after = Ceto
| mp_category = [[Astronomy:Trans-Neptunian object|TNO]]<br />[[Astronomy:Centaur (minor planet)|Centaur]]–extended<ref name=Buie>{{cite web
  |author=Marc W. Buie
  |date=2006-05-05
  |title=Orbit Fit and Astrometric record for 65489
  |publisher=SwRI (Space Science Department)
  |url=http://www.boulder.swri.edu/~buie/kbo/astrom/65489.html
  |access-date=2009-01-25}}</ref>
| orbit_ref = <ref name=jpldata>{{cite web
  |type=2006-05-05 last obs
  |title=JPL Small-Body Database Browser: 65489 Ceto (2003 FX128)
  |url=https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=65489
  |access-date=25 March 2016}}</ref> 
| epoch = 13 January 2016 ([[Astronomy:Julian day|JD]] 2457400.5)
| aphelion = {{Convert|187.74|AU|Tm|abbr=on|lk=on}}
| perihelion = {{Convert|17.8498|AU|Tm|abbr=on}}
| semimajor = {{Convert|102.79|AU|Tm|abbr=on}}
| eccentricity = 0.82635
| period = 1042.22 [[Astronomy:Julian year|yr]] (380669.7 [[Astronomy:Julian year|d]])
| avg_speed = 
| inclination = 22.266°
| asc_node = 171.85°
| mean_anomaly = 9.1219[[Degree (angle)|°]]
| arg_peri = 320.086°
| satellites = Phorcys {{IPAc-en|ˈ|f|ɔər|s|ᵻ|s}}<br />({{val|171|10}}<ref name=TNOsCool4/> ~ {{val|132|+6|-14|u=km}}<ref name="Grundy2007"/> in diameter)
| dimensions = {{val|223|10|u=km}}<!--281 is for a combined Ceto-Phorcys--><ref name=TNOsCool4>Santos-Sanz, P., Lellouch, E., Fornasier, S., Kiss, C., Pal, A., Müller, T. G., Vilenius, E., Stansberry, J., Mommert, M., Delsanti, A., Mueller, M., Peixinho, N., Henry, F., Ortiz, J. L., Thirouin, A., Protopapa, S., Duffard, R., Szalai, N., Lim, T., Ejeta, C., Hartogh, P., Harris, A. W., & Rengel, M. (2012). [https://arxiv.org/abs/1202.1481 “TNOs are Cool”: A Survey of the Transneptunian Region IV - Size/albedo characterization of 15 scattered disk and detached objects observed with ''Herschel'' Space Observatory-PACS]</ref><br />{{val|174|+16|-18|u=km}}<ref name="Grundy2007"/>
| mass = {{val|5.4|0.4|e=18|u=kg}} (system)<ref name="Grundy2007">{{cite journal
  |last=Grundy |first=W.M.
  |author2=Stansberry, J.A.
  |author3=Noll K.S.
  |author4=Stephens, D.C.
  |title=The orbit, mass, size, albedo, and density of (65489) Ceto/Phorcys: A tidally-evolved binary Centaur
  |journal=Icarus |date=2007
  |arxiv=0704.1523
  |doi=10.1016/j.icarus.2007.04.004
  |volume=191  |issue=1
 |pages=286–297
|bibcode=2007Icar..191..286G
|s2cid=1532765
 |display-authors=0}}</ref>
| density = {{val|1.37|u=g/cm3}} (system)<ref name=Grundy2007/>
| surface_grav = {{val|3.3|u=cm/s2}}<ref name=Grundy2007/>
| escape_velocity = 
| sidereal_day = 
| axial_tilt = 
| pole_ecliptic_lat = 
| pole_ecliptic_lon = 
| albedo = {{val|0.056|0.006}}<ref name=TNOsCool4/><br /> {{val|0.084|0.02}}<ref name=Grundy2007/>
| temperatures= 
| temp_name1 = 
| mean_temp_1 = 
| max_temp_1 = 
| temp_name2 = 
| max_temp_2 = 
| spectral_type = 
| abs_magnitude = {{val|6.54|0.06}},<ref name=TNOsCool4/> 6.4<ref name=jpldata/>
| rotation = {{Convert|4.43|h|d|abbr=on|lk=on}}
| observation_arc = 9239 days (25.30 yr)
| uncertainty = 2
| moid = {{Convert|16.895|AU|Tm|abbr=on}}
| jupiter_moid = {{Convert|12.7433|AU|Tm|abbr=on}}
| mean_motion = 0.00094570°/day
}}

'''65489 Ceto''', as a binary also '''(65489) Ceto/Phorcys''',<ref name="Grundy2007"/> is a [[Astronomy:Binary asteroid|binary]] [[Astronomy:Trans-Neptunian object|trans-Neptunian object]] (TNO) discovered on March 22, 2003, by Chad A. Trujillo and [[Biography:Michael E. Brown|Michael Brown]] at [[Organization:Palomar Observatory|Palomar]]. It is named after the sea goddess Ceto from Greek mythology.  It came to [[Astronomy:Apsis|perihelion]] in 1989.<ref name=jpldata/>

== Physical characteristics ==
[[File:65489 Ceto.tiff|thumb|left|Polar view of Ceto's orbit]]
65489 Ceto is an example of a close binary TNO system in which the components are of similar size. Combined observations with the infrared [[Astronomy:Spitzer Space Telescope|Spitzer Space Telescope]] and the [[Astronomy:Hubble Space Telescope|Hubble Space Telescope]] allow the diameter of Ceto itself to be estimated at {{val|174|+16|-18|u=km}} and the diameter of Phorcys at {{val|132|+6|-14|u=km}}, assuming equal [[Earth:Albedo|albedo]] for both components.<ref name="Grundy2007"/>

The binary nature of Ceto enables direct calculation of the system mass, allowing estimation of the masses of the components and providing additional constraints on their composition. The estimated [[Physics:Density|density]] of Ceto is {{val|1.37|+0.66|-0.32|u=g/cm3}}, significantly less than that of the large TNOs (Haumea: {{val|3.0|u=g/cm3}}, [[Astronomy:Eris (dwarf planet)|Eris]]: 2.26, [[Astronomy:Pluto|Pluto]]: 2.03, [[Astronomy:Charon (moon)|Charon]]: 1.65) but significantly more than that of smaller TNOs (e.g. {{val|0.7|u=g/cm3}} for {{mpl|(26308) 1998 SM|165}}). Phorcys has a mass of about {{val|1.67e18|u=kg}}.<ref name=Grundy2007/> Unless the bodies are [[Earth:Porosity|porous]], the density is consistent with rock–ice composition, with rock content around 50%.<ref name="Grundy2007"/>

It has been suggested that tidal forces, together with other potential heat sources (e.g. collisions or <sup>26</sup>[[Chemistry:Aluminium|Al]] [[Physics:Radioactive decay|decay]]) might have raised the temperature sufficiently to crystallise [[Physics:Amorphous solid|amorphous]] ice and reduce the void space inside the object.
The same tidal forces could be responsible for the quasi-circular orbits of the components of Ceto.<ref name="Grundy2007"/>

Ceto is listed on [[Biography:Michael E. Brown|Michael Brown]]'s website as [[Astronomy:List of possible dwarf planets|possibly a dwarf planet]].<ref name="Brown-dplist">{{cite web
 |title=How many dwarf planets are there in the outer solar system? (updates daily) 
 |publisher=[[Organization:California Institute of Technology|California Institute of Technology]] 
 |author=Michael E. Brown 
 |url=http://www.gps.caltech.edu/~mbrown/dps.html 
 |access-date=2015-10-03 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20111018154917/http://www.gps.caltech.edu/~mbrown/dps.html 
 |archive-date=2011-10-18 
}}</ref>

== Satellite==
{{Infobox planet
 | minorplanet = yes
 |name             = Phorcys
 | image           = 
 | image_size      = 
 | caption         = 
 |discoverer       = Keith S. Noll ''et al.''
 |discovered       = 2006 April 11
 |alt_names        = {{nowrap|(65849) Ceto I Phorcys}}
 |pronounced       = {{IPAc-en|ˈ|f|ɔər|s|ᵻ|s}}
 |named_after      = Phorcys
 |adjectives       = Phorcynian {{IPAc-en|f|ɔr|ˈ|s|ɪ|n|i|ə|n}},<ref>Origin of the Homeric Poems, in ''The Quarterly Review'', vol. LXXXVII, Jan. 1831, p. 164</ref><!--this refers to the harbor of Phorcys, but per Liddell & Scott and Lewis & Short, Φόρκῡνος / Phorcȳnos is an alt. root/genitive of the myth figure as well.--> Phorcyan {{IPAc-en|ˈ|f|ɔr|s|i|ə|n}}<ref>Henry Tytler (1828) ''Punics of Caius Silius Italicus'', vol. 1, p. 48 [with the stress on the first syllable, consistent with the short 'y' in Greek and Latin]</ref><!--these Phorcyan caves refer to the gorgons, the daughters of Phorcys, as 'Phorcyan', but per Lewis & Short, Phorcys or Phorcȳnis in this sense has the genitive forms Phorcydos, Phorcȳnĭdos, whereas the Phorcys here has the genitive form Phorcyos (thus Phorcyan). However, Thomos Clark's 1862 edition of Ovid's ''Metamorphosis'' translates Latin Phorcydas as 'Phorcyan' (p. 162), so the distinction does not seem to be maintained in English.--> <ref>The form ''Phorcian'' is also found, but derives from the assimilated Latin ''Phorcus / Phorci'' rather than ''Phorcys / Phorcyos''.[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0059%3Aentry%3DPhorcus]</ref>
 |orbit_ref        = 
 |semimajor        = 
 |eccentricity     = 
 |period           = 
 |inclination      = 
 |satellite_of     = {{dp|Ceto}}
 |physical_ref     = <ref>[http://johnstonsarchive.net/astro/astmoons/am-65489.html Johnston's Archive]</ref>
 |dimensions       = {{val|171|10}}<ref name=TNOsCool4/><br />{{val|132|+6|-14|u=km}}.<ref name="Grundy2007"/><br />primary/secondary ratio {{val|0.76|0.01}}
 |mass             = 
 |density          = 
 |albedo           = 
 |spectral_type    = 
 |magnitude        = ΔM = {{val|0.56|0.03}}
 |abs_magnitude    = 
}}

Ceto's satellite was identified as a [[Astronomy:Binary asteroid|binary]] on April 11, 2006, by K. Noll, H. Levison, W. Grundy and D. Stephens using the Hubble Space Telescope; the object was named '''Phorcys''', formally '''(65849) Ceto I Phorcys''', after the Greek sea god. Using an extended definition of a [[Astronomy:Centaur (minor planet)|centaur]] as an object on a non-resonant (unstable) orbit with its perihelion inside the orbit of Neptune,<ref name="DES_Elliot2005">
  {{cite journal
  |author=J. L. Elliot
  |author2=S. D. Kern
  |author3=K. B. Clancy
  |author4=A. A. S. Gulbis
  |author5=R. L. Millis
  |author6=M. W. Buie
  |author7=L. H. Wasserman
  |author8=E. I. Chiang
  |author9=A. B. Jordan
  |author10=D. E. Trilling
  |author11=K. J. Meech
  |name-list-style=amp
  |title=The Deep Ecliptic Survey: A Search for Kuiper Belt Objects and Centaurs. II. Dynamical Classification, the Kuiper Belt Plane, and the Core Population.
  |journal=The Astronomical Journal
  |volume=129|date=February 2005
  |issue=2
 |url=http://occult.mit.edu/_assets/documents/publications/Elliot2005AJ129.1117.pdf |page=1117
  |bibcode=2005AJ....129.1117E 
  |doi=10.1086/427395|doi-access=free
  }}
</ref>
the Ceto system can be considered the second known binary centaur.<ref name="Grundy2007"/>

Phorcys's diameter has been estimated to be {{val|171|10}}<ref name=TNOsCool4/> and {{val|132|+6|-14|u=km}}.<ref name="Grundy2007"/>

==See also==
*[[Astronomy:List of Solar System objects by size|List of Solar System objects by size]]

== References ==
{{reflist}}

== External links ==
* Binary asteroids at [http://www.johnstonsarchive.net/astro/asteroidmoons.html#1 johnstonsarchive]
* {{JPL small body|id=65489}}

{{Small Solar System bodies}}

{{DEFAULTSORT:Ceto}}
[[Category:Named minor planets]]

{{Sourceattribution|65489 Ceto}}