View source for Polydeuces (moon)

{{good article}}
{{Short description|Trojan moon of Saturn}}
{{Use dmy dates|date=June 2023}}
{{Infobox planet
 | name            = Polydeuces
 | image           = Polydeuces PIA08209.png
 | image_scale     =
 | image_alt       = A blurry image of Polydeuces from afar, showing a vaguely ellipsoidal object
 | caption         = Polydeuces imaged approximately {{cvt|73000|km|mi}} away from the ''[[Cassini (spacecraft)|Cassini]]'' spacecraft on 22 May 2006
 | mpc_name        = Saturn XXXIV
 | alt_names       = S/2004 S 5
 | named_after     = [[Polydeuces (mythology)|Πολυδεύκης]] ''Polydeykēs''
 | pronounced      = {{IPAc-en|ˌ|p|ɒ|l|ᵻ|ˈ|dj|uː|s|iː|z}}<ref>{{Cite encyclopedia |url=http://www.lexico.com/definition/Polydeuces |archive-url=https://web.archive.org/web/20211024091841/https://www.lexico.com/definition/Polydeuces |url-status=dead |archive-date=24 October 2021 |title=Polydeuces |dictionary=[[Lexico]] UK English Dictionary |publisher=[[Oxford University Press]]}}</ref>
 | adjectives      = {{nowrap|Polydeucean {{IPAc-en|ˌ|p|ɒ|l|ᵻ|dj|uː|ˈ|s|iː|ə|n}}<ref>Lundström (1997) ''Eranos,'' v. 95</ref>}}<br/>{{nowrap|Polydeucian {{IPAc-en|ˌ|p|ɒ|l|ᵻ|ˈ|dj|uː|s|i|ə|n}}<ref>Levin (1971) ''Apollonius' Argonautica'', v. 1, p. 139</ref>}}
 | discovery_ref   = <ref name="jpl-satdisc"/><ref name="Gazetteer"/>
 | discoverer      = [[Cassini (spacecraft)|Cassini]] Imaging Science Team{{efn|name=team|Members of the Cassini Imaging Science Team include (in alphabetical surname order): Andre Brahic, Joe Burns, Tony DelGenio, Luke Dones, Andy Ingersoll, Torrence Johnson, Alfred McEwen, [[Carl D. Murray]], Gerhard Neukum, [[Carolyn Porco]], Steve Squyres, Peter Thomas, Joe Veverka, and Bob West.<ref name="CICLOPS-ISS"/>}}
 | discovered      = 21 October 2004<br/>(date of discovery images)<ref name="Murray2005"/>{{rp|page=223}}
 | orbit_ref       = <ref name="jpl-satelem"/><ref name="Jacobson2022"/>{{rp|page=9}}
 | epoch           = 1 January 2000 12:00 UT<br/>([[Julian date|JD]] 2451545.0)
 | earliest_precovery_date = 2 April 2004<ref name="Spitale2006"/>{{rp|page=695, 702}}<ref name="Jacobson2008"/>{{rp|page=261}}
 | semimajor       = {{val|377600|u=km}}
 | avg_speed       = {{val|10.03|u=km/s}}<ref name="Rossignoli2019"/>{{rp|page=2}}
 | eccentricity    = {{val|0.019}}
 | period          = {{val|2.736916|ul=d}}<ref name="jpl-satelem"/>
 | inclination     = {{val|0.2|ul=°}}{{efn|name=inclination|The mean orbital inclination is given with respect to the Polydeuces's local [[Laplace plane]].<ref name="jpl-satelem"/><ref name="Jacobson2022"/>{{rp|page=9}} Conincidentally, the Laplace plane inclination value is close to the mean orbital inclination with respect to Saturn's equator, given as {{val|0.1774|u=°}} in Spitale et al. (2006), Table 6.<ref name="Spitale2006"/>{{rp|page=695, 698}}}}
 | satellite_of    = [[Saturn]]
 | group           = [[Trojan moon|L<sub>5</sub> Dione trojan]]
 | dimensions      = {{val|3.50|x|3.10|x|2.62}}&nbsp;km<br/>(±&nbsp;{{val|0.40|x|0.40|x|0.40}}&nbsp;km)<ref name="Hedman2020"/>{{rp|page=7}}
 | mean_diameter   = {{val|3.06|0.40|u=km}}<ref name="Hedman2020"/>{{rp|page=7}}
 | volume          = {{val|15|u=km3}}{{efn|Volume calculated from Polydeuces's volume-equivalent sphere radius of {{val|1.53|0.20|u=km}} given by Hedman et al. (2020).<ref name="Hedman2020"/>{{rp|page=7}}}}
 | mass            = {{val|8|e=12|u=kg|p=≈&thinsp;}} (assumed; unmeasured){{efn|Mass calculated by multiplying Polydeuces's volume with its assumed density of {{val|500|u=kg/m3}} according to the formula <math>{M} = \rho V</math>.}}
 | density         = {{val|0.5|u=g/cm3|p=≈&thinsp;}} (assumed; unmeasured)<ref name="Polydeuces-Numbers"/><ref name="Cuk2016"/>{{rp|page=3}}<ref name="Rossignoli2019"/>{{rp|page=2}}
 | surface_grav    = ≈&thinsp;{{Gr|8e-9|1.75|4}}&nbsp;m/s<sup>2</sup> at longest axis<br/>to ≈&thinsp;{{Gr|8e-9|1.31|4}}&nbsp;m/s<sup>2</sup> at poles{{efn|[[Surface gravity]] ''g'' is calculated from the formula <math>g = \frac{GM}{r^2}</math>, where ''G'' is the [[gravitational constant]], ''M'' is the body's mass, and ''r'' is the body's radius (or [[semi-axis]] if nonspherical). For Polydeuces, its mass is approximately {{val|8|e=12|u=kg}} for an assumed density of {{val|500|u=kg/m3}}. For Polydeuces's longest semi-axis of {{val|1.75|u=km}},<ref name="Hedman2020"/>{{rp|page=7}} the surface gravity would be about {{Gr|8e-9|1.75|4}}&nbsp;m/s<sup>2</sup>, while for Polydeuces's shortest (polar) semi-axis of {{val|1.31|u=km}}, the surface gravity would be about {{Gr|8e-9|1.31|4}}&nbsp;m/s<sup>2</sup>.}}
 | escape_velocity = ≈&thinsp;{{V2|8e-9|1.75|4}}&nbsp;km/s at longest axis<br/>to ≈&thinsp;{{V2|8e-9|1.31|4}}&nbsp;km/s at poles<!-- V2 template uses mass in terms of e+21 kg, radius in terms of km, and number of decimal places -->{{efn|[[Escape velocity]] ''v''<sub>e</sub> is calculated from the formula <math>v_e = \sqrt {\frac{2GM}{r}}</math>, where ''G'' is the [[gravitational constant]], ''M'' is the body's mass, and ''r'' is the body's radius (or [[semi-axis]] if nonspherical). For Polydeuces, its mass is approximately {{val|8|e=12|u=kg}} for an assumed density of {{val|500|u=kg/m3}}. For Polydeuces's longest semi-axis of {{val|1.75|u=km}},<ref name="Hedman2020"/>{{rp|page=7}} the escape velocity would be about {{V2|8e-9|1.75|4}}&nbsp;km/s, while for Polydeuces's shortest (polar) semi-axis of {{val|1.31|u=km}}, the escape velocity would be about {{V2|8e-9|1.31|4}}&nbsp;km/s.}}
 | rotation        = [[synchronous rotation|assumed synchronous]]<ref name="Rossignoli2019"/>{{rp|page=4}}
 | axial_tilt      = 
 | albedo          = 
}}

'''Polydeuces''' {{IPAc-en|ˌ|p|ɒ|l|ᵻ|ˈ|dj|uː|s|iː|z}}, also designated '''Saturn XXXIV''', is a small [[trojan (celestial body)|trojan]] [[Moons of Saturn|moon of Saturn]] occupying the trailing {{L5}} [[Lagrange point]] of [[Dione (moon)|Dione]]. It was discovered by the Cassini Imaging Science Team in images taken by the [[Cassini–Huygens|''Cassini'' space probe]] on 21 October 2004. With a [[mean diameter]] of about {{cvt|3|km|mi}}, Polydeuces is thought to have a smooth surface coated with fine, icy particles accumulated from the [[Cryovolcano|cryovolcanic]] plumes of [[Enceladus]]. In its orbit around Saturn, Polydeuces periodically drifts away from Dione's Lagrange point due to gravitational [[perturbation (astronomy)|perturbations]] by other nearby moons of Saturn. Of the four known trojan moons of Saturn, Polydeuces exhibits the largest displacement from its Lagrange point.

== Discovery ==
[[File:Polydeuces discovery images annotated.gif|thumb|left|''Cassini'' discovery images of Polydeuces on 21 October 2004|alt=Cassini's discovery images of Polydeuces from 21 October 2004 show the moon as a faint, pixelated dot moving against the static background stars. The images are partially obscured by Saturn's bright glare emanating from the right.]]

Polydeuces was discovered by the Cassini Imaging Science Team{{efn|name=team}} on 24 October 2004 while routinely investigating images taken by the ''[[Cassini–Huygens|Cassini]]'' [[space probe]] earlier on 21 October 2004.<ref name="Murray2005"/>{{rp|page=223}} The images were visually inspected through the [[Blink comparator|blink comparison]] technique, which revealed any potential moons that moved relative to the background stars. The discovery images consisted of four frames taken with ''Cassini''{{'}}s wide-angle camera over less than six minutes, which showed Polydeuces moving 3–6 pixels per frame.{{efn|1=The discovery announcement of Polydeuces in IAUC 8432 mistakenly reports that it was discovered in narrow-angle ''Cassini'' images on 21 October 2004.<ref name="IAUC8432"/> All ''Cassini'' images containing Polydeuces on 21 October 2004 were taken with the wide-angle camera, as reported in Murray et al. (2005), Table 1<ref name="Murray2005"/>{{rp|page=224–225}} and shown in [https://opus.pds-rings.seti.org/#/instrument=Cassini+ISS&observationtype=Image&time1=2004-10-21T00:00:00.000&time2=2004-10-22T00:00:00.000&qtype-time=any&unit-time=ymdhms&cols=opusid,instrument,planet,target,time1,observationduration&widgets=time,instrument,observationtype,target&order=time1,opusid&view=browse&browse=data&cart_browse=gallery&startobs=1&cart_startobs=1&detail= NASA's Outer Planets Unified Search tool] for archived ''Cassini'' data.}}<ref name="Murray2005"/>{{rp|page=223}} The observed motion of Polydeuces immediately suggested that it could be orbiting Saturn at the distance of one of the large moons, [[Dione (moon)|Dione]], possibly sharing its orbit in a [[co-orbital configuration]].<ref name="Murray2005"/>{{rp|page=223}}

By 4 November 2004, the Cassini Imaging Science Team obtained more ''Cassini'' images of Polydeuces, including two frames taken on 2 November 2004 and another two predating the discovery images by three hours.<ref name="Murray2005"/>{{rp|page=223–226}} Preliminary [[orbit determination]]s using these images confirmed that Polydeuces was a co-orbital [[Trojan (celestial body)|trojan moon]] residing around Dione's {{L5}} [[Lagrange point]].<ref name="Murray2005"/>{{rp|page=226}} With the aid of [[ephemeris]] predictions from Polydeuces's newly determined orbit, the Cassini Imaging Science Team was able to identify 52 [[precovery|pre-discovery]] detections of Polydeuces in ''Cassini''{{'}}s narrow-angle camera images taken between 9 April 2004 and 9 May 2004.<ref name="Murray2005"/>{{rp|page=226}} The [[International Astronomical Union]] (IAU) announced the discovery of Polydeuces on 8 November 2004.<ref name="IAUC8432"/> Besides Polydeuces, ''Cassini'' has discovered five other objects orbiting Saturn in 2004: [[Methone (moon)|Methone]], [[Pallene (moon)|Pallene]], [[S/2004 S 3]], [[S/2004 S 4]], and [[S/2004 S 6]].<ref name="Porco2005"/>{{rp|page=1226–1227}}

After the discovery announcement, ''Cassini'' was retasked to begin targeted observations of Polydeuces in January 2005 to better determine its orbit.<ref name="Murray2005"/>{{rp|page=226}} In 2006, researchers found even earlier ''Cassini'' pre-discovery images of Polydeuces taken on 2 April 2004.<ref name="Spitale2006"/>{{rp|page=695, 702}}

== Name ==
The name Polydeuces was approved and announced by the IAU Working Group on Planetary System Nomenclature on 21 January 2005.<ref name="IAUC8471"/> In [[Greek mythology]], [[Castor and Pollux|Polydeuces]] is another name for Pollux, who is the twin brother of [[Castor and Pollux|Castor]] and the son of [[Zeus]] and [[Leda (mythology)|Leda]].<ref name="Gazetteer"/> Polydeuces is also known by its official [[Naming of moons#Roman numeral designations|Roman numeral designation]] Saturn XXXIV (34th moon of Saturn discovered) and was previously known by its [[Provisional designation in astronomy|provisional designation]] {{nowrap|S/2004 S 5}}, which was given by the IAU when it announced the moon's discovery.<ref name="IAUC8432"/><ref name="IAUC8471"/>

== Orbit ==
[[File:Lagrange very massive.svg|thumb|left|The trojan points are located on the {{L4|nolink=yes}} and {{L5|nolink=yes}} [[Lagrange point]]s, on the orbital path of the secondary object Dione (blue), around the primary object Saturn (yellow). All of the Lagrange points are highlighted in red.]]
[[File:Animation of Polydeuces's orbit relative to Saturn and Dione.gif|thumb|left|Animation of Polydeuces's [[Libration point orbit|librating]] [[tadpole orbit]] in a [[rotating reference frame]] with respect to Dione<br>{{legend2|Magenta|Polydeuces }}{{·}}{{legend2|Cyan|Helene}}{{·}}{{legend2|Lime|Dione}}{{·}}{{legend2|DarkOrange|Saturn}}]]

Polydeuces is an [[inner moon]] of Saturn in a [[co-orbital configuration]] with Dione, meaning they share the same orbit.<ref name="Jacobson2008"/>{{rp|page=261}}<ref name="Thomas2020"/>{{rp|page=2}} Together with Dione and its other co-orbital companion [[Helene (moon)|Helene]], Polydeuces orbits Saturn in 2.74 days at an average distance of {{cvt|377600|km|mi}} from the planet's center, between the orbits of [[Tethys (moon)|Tethys]] and [[Rhea (moon)|Rhea]].<ref name="jpl-satelem"/> Due to gravitational [[perturbation (astronomy)|perturbations]] by other nearby moons of Saturn, Polydeuces's orbital radius can vary by ±{{cvt|7660|km|mi}} over time.<ref name="Murray2005"/>{{rp|page=232}} Its orbit is closely aligned with Saturn's equatorial plane with a low [[orbital inclination]] of 0.2°.{{efn|name=inclination}}

Polydeuces has a slightly [[Elliptic orbit|elliptical orbit]] with an [[orbital eccentricity|eccentricity]] of 0.019, which is unusually higher than Dione's eccentricity of 0.002. While Dione's eccentricity is known to result from its 1:2 [[orbital resonance|mean-motion orbital resonance]] with [[Enceladus]], the effects of this resonance are too weak to explain Polydeuces's relatively high eccentricity.<ref name="Murray2005"/>{{rp|page=233}} One possible explanation is that Polydeuces always had an eccentric orbit since its formation because its orbit did not change much over billions of years.<ref name="Murray2005"/>{{rp|page=233}}

Polydeuces resides around Dione's {{L5}} [[Lagrange point]] trailing 60° behind Dione in its orbit, which makes Polydeuces a [[Trojan (celestial body)|trojan moon]] of Dione. The Lagrange points are locations where the gravitational pulls of Dione and Saturn balance out, allowing for stable co-orbital configurations in Dione's trojans.<ref name="Polydeuces-InDepth"/> Dione's other co-orbital moon, Helene, is a trojan residing around the {{L4}} Lagrange point leading 60° ahead of Dione. Trojan moons are not unique to Dione; another large moon of Saturn, Tethys, also has two trojans, named [[Telesto (moon)|Telesto]] and [[Calypso (moon)|Calypso]], which reside in its {{L4|nolink=yes}} and {{L5|nolink=yes}} Lagrange points, respectively.<ref name="Murray2005"/>

Because of perturbations by other moons of Saturn, Polydeuces does not stay exactly 60° behind Dione; its [[angular distance]] from Dione oscillates or [[Libration point orbit|librates]] over time.<ref name="Murray2005"/>{{rp|page=231}} Of Saturn's four known trojan moons, Polydeuces librates the farthest from its Lagrange point: its angular distance behind Dione oscillates from 33.9° to 91.4° with a period of {{convert|790.931|d|yr|sigfig=3|abbr=off}}.<ref name="Spitale2006"/>{{rp|page=702}}{{efn|The angular distance minimum and maximum are calculated by adding –60° (negative because {{L5|nolink=yes}} is behind Dione) to Polydeuces's libration [[amplitude]]s of –31.41° and +26.06° given by Spitale et al. (2006)<ref name="Spitale2006"/>{{rp|page=702}}}} In a [[rotating reference frame]] with respect to Dione's orbit, Polydeuces appears to travel in a looping path around Dione's {{L5|nolink=yes}} point due to its varying [[Relative velocity|relative speed]] and radial distance from Saturn in its perturbed eccentric orbit.<ref name="Murray2005"/>{{rp|page=231–232}} Polydeuces's apparent looping motion combined with its librating angular distance from Dione forms a [[tadpole orbit]] about Dione's {{L5|nolink=yes}} point.<ref name="Murray2005"/>{{rp|page=231}}

== Origin ==
Polydeuces is thought to have formed by [[Accretion (astrophysics)|accreting]] out of leftover debris trapped in Dione's {{L5|nolink=yes}} Lagrange point, in a similar process experienced by Saturn's other trojan moons. This process likely took place at an intermediate stage of the formation of Saturn's moons, when Tethys and Dione have not finished forming and gases have become depleted in Saturn's [[circumplanetary disk]].<ref name="Izidoro2010"/>{{rp|page=2133}}<ref name="Rossignoli2019"/>{{rp|page=4}} Mean-motion orbital resonances by other nearby moons did not appear to play a significant role in the formation of the trojan moons.<ref name="Izidoro2010"/>{{rp|page=2139}}

Dynamical modeling of the trojan moons' formation suggests that Tethys's and Dione's {{L4|nolink=yes}} and {{L5|nolink=yes}} Lagrange points should have started with similar amounts of material for trojan moons to form with roughly similar sizes.<ref name="Izidoro2010"/>{{rp|page=2136}} However, this is not the case for Dione's trojans, Helene and Polydeuces, whose masses significantly differ by more than an order of magnitude. As of yet, this mass asymmetry in Dione's {{L4|nolink=yes}} and {{L5|nolink=yes}} trojans remains unexplained.<ref name="Izidoro2010"/>{{rp|page=2139}}

== Physical characteristics ==
{{As of|2020}}, the most recent estimate for Polydeuces's dimensions is {{cvt|3.50 x 3.10 x 2.62|km|mi}}, based on resolved ''Cassini'' imagery of the moon from 2015.<ref name="Hedman2020"/>{{rp|page=7, 30}} These dimensions correspond to a volume-equivalent mean diameter of {{cvt|3.06|km|mi}} for Polydeuces.<ref name="Hedman2020"/>{{rp|page=7}} ''Cassini''{{'}}s highest-resolution images of Polydeuces from 2015 show that it has an elongated shape, with a relatively smooth [[lunar limb|limb]] deviating from a simple [[ellipsoid]].<ref name="Hedman2020"/>{{rp|page=30}} Polydeuces presumably rotates [[synchronous rotation|synchronously]] with its orbital period, similar to the rest of Saturn's trojan moons.<ref name="Rossignoli2019"/>{{rp|page=4}}

Little is known about Polydeuces's other physical properties because it was never approached up close by ''Cassini'' or any other space mission to Saturn.<ref name="Thomas2020"/>{{rp|page=3}} Because of its very small size, Polydeuces's gravitational perturbations on the trajectory of ''Cassini'' spacecraft and other Saturnian moons are negligible, which prevents the measurement of the moon's mass and density.<ref name="Jacobson2022"/>{{rp|page=5}} In spite of this, researchers assume that Polydeuces has a density similar to those of Saturn's small inner moons, whose average density is {{val|0.5|u=g/cm3}},<ref name="Polydeuces-Numbers"/><ref name="Cuk2016"/>{{rp|page=3}}<ref name="Rossignoli2019"/>{{rp|page=2}}<ref name="Thomas2020"/>{{rp|page=2}}

{{multiple image
 |direction = horizontal
 |align = right
 |total_width = 300
 |header = ''Cassini'' images of Polydeuces
 |image1 = Polydeuces N1809910848.png |caption1 = Distance approx. {{cvt|44800|km|mi}}, 9 May 2015
 |image2 = Polydeuces N1813127275 enhanced.png |caption2 = Distance approx. {{cvt|34800|km|mi}}, 16 June 2015. Polydeuces is illuminated by both Saturn and the Sun.
}}

Polydeuces's small size makes it prone to [[Disrupted planet|disruption]] by [[impact event]]s. Depending on the size-frequency of impactors in the Saturnian system, Polydeuces is predicted to have suffered at least one disruptive impact in the last one billion years.<ref name="Rossignoli2019"/>{{rp|page=11}} This implies that Polydeuces is either very young with an age of less than one billion years, or it is a primordial moon that has consistently reaccreted from each disruptive impact over the Saturnian system's 4.5 billion-year lifespan.<ref name="Rossignoli2019"/>{{rp|page=13}}

Polydeuces has a bright and likely smooth surface due to the accumulation of fine water ice particles from the surrounding [[Rings of Saturn#E Ring|E Ring]], which is generated by the [[Cryovolcano|cryovolcanic]] plumes of Enceladus.<ref name="Hirata2014"/><ref name="Rossignoli2019"/>{{rp|page=11}} Because of its small size, any [[impact crater|crater]]s on Polydeuces would be completely buried in E Ring material, giving it a craterless appearance resembling [[Methone (moon)|Methone]] or [[Pallene (moon)|Pallene]].<ref name="Hirata2014"/><ref name="Rossignoli2019"/>{{rp|page=11}} Its [[geometric albedo]] is unknown since it has never been observed at low [[phase angle (astronomy)|phase angles]].<ref name="Hedman2020"/>{{rp|page=10, 30}} ''Cassini'' imagery shows that Polydeuces has a uniform surface brightness across its leading and trailing hemispheres.<ref name="Hedman2020"/>{{rp|page=23}} Its surface is about as bright as Dione's but darker than Helene's.<ref name="Hedman2020"/>{{rp|page=23}} The trojan moons of Tethys exhibit a similar difference in surface brightness, where Calypso is brighter than Telesto and Tethys.<ref name="Hedman2020"/>{{rp|page=23}} The reason for these brightness asymmetries in the trojan moons of Dione and Tethys remains unknown; possible explanations include an asymmetric distribution of E Ring particles or recent impacts that brightened Helene and Calypso.<ref name="Hedman2020"/>{{rp|page=27–28}}

== Exploration ==
''Cassini'' is the only space mission to Saturn that has made targeted observations of Polydeuces.<ref name="Murray2005"/> Over the 13-year span of ''Cassini''{{'}}s mission in orbit around Saturn, the spacecraft has made 22 close approaches within {{cvt|130000|km|mi}} of Polydeuces.<ref name="PDS-Tour"/> ''Cassini''{{'}}s closest encounter with Polydeuces took place on 17 February 2005, when it passed {{cvt|6446.7|km|mi}} from Polydeuces while moving outbound from [[periapse]].<ref name="PDS-Tour"/> However, ''Cassini'' did not take any images of Polydeuces on that date.<ref name="Spitale2006-T3"/> The only encounters where ''Cassini'' has taken resolved images of Polydeuces were on 22 May 2006, 10 May 2015, and 16 June 2015, at closest approach distances of {{cvt|64089.9|km|mi}}, {{cvt|33997.8|km|mi}}, and {{cvt|34794.3|km|mi}}, respectively.<ref name="PDS-Tour"/><ref name="Hedman2020"/>{{rp|page=31}}{{efn|1=Hedman et al. (2020) list all resolved ''Cassini'' observations of Polydeuces in Table 7, but they only give the image IDs of these observations.<ref name="Hedman2020"/>{{rp|page=31}} Inputting these image IDs into [https://opus.pds-rings.seti.org/ NASA's Outer Planets Unified Search query form] shows the date on which these images were taken.}} ''Cassini''{{'}}s two close encounters in 2015 provided the first images where Polydeuces was larger than 10 pixels across.<ref name="Hedman2020"/>{{rp|page=30}}

== See also ==
* [[Telesto (moon)|Telesto]] and [[Calypso (moon)|Calypso]], trojan moons of [[Tethys (moon)|Tethys]] at its {{L4|nolink=yes}} and {{L5|nolink=yes}} Lagrange points, respectively
* [[Janus (moon)|Janus]] and [[Epimetheus (moon)|Epimetheus]], two inner moons of Saturn in a [[co-orbital configuration#Exchange orbits|co-orbital exchange orbit]] with each other

== Notes ==
{{notelist}}

== References ==
{{reflist|refs=

<ref name="jpl-satdisc">{{cite web
 |title        = Planetary Satellite Discovery Circumstances
 |url          = https://ssd.jpl.nasa.gov/sats/discovery.html
 |publisher    = [[Jet Propulsion Laboratory]]
 |date         = 23 May 2023
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}}</ref>

<ref name="Gazetteer">{{cite web
 |title        = Planet and Satellite Names and Discoverers
 |url          = https://planetarynames.wr.usgs.gov/Page/Planets#SaturnianSystem
 |work         = Gazetteer of Planetary Nomenclature
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}}</ref>

<ref name="jpl-satelem">{{cite web
  |title      = Planetary Satellite Mean Orbital Parameters
  |url      = https://ssd.jpl.nasa.gov/sats/elem/sep.html
  |publisher      = [[Jet Propulsion Laboratory]]
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  |url-status      = live
  }}</ref>

<ref name="Polydeuces-InDepth">{{cite web
 |title        = Polydeuces In Depth
 |url          = https://solarsystem.nasa.gov/moons/saturn-moons/polydeuces/in-depth/
 |work         = Solar System Exploration
 |publisher    = NASA
 |date         = 19 December 2019
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 |url-status   = live
}}</ref>

<ref name="Polydeuces-Numbers">{{cite web
 |title        = Polydeuces By the Numbers
 |url          = https://solarsystem.nasa.gov/moons/saturn-moons/polydeuces/by-the-numbers/
 |work         = Solar System Exploration
 |publisher    = NASA
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 |url-status   = live
}}</ref>

<ref name="PDS-Tour">{{cite web
  |title      = Cassini Tour Event Summary: Planned Observations of Small Satellites
  |url        = https://pds-atmospheres.nmsu.edu/data_and_services/atmospheres_data/Cassini_PDS3/logs/small%20satellites_Events_as_planned.htm
  |work       = PDS Atmospheres Node
  |publisher  = NASA
  |access-date = 6 June 2023
  |url-status = live
  |archive-url = https://web.archive.org/web/20230606003311/https://pds-atmospheres.nmsu.edu/data_and_services/atmospheres_data/Cassini_PDS3/logs/small%20satellites_Events_as_planned.htm
  |archive-date = 6 June 2023}}</ref>

<ref name="CICLOPS-ISS">{{cite web
  |title      = Cassini Imaging Science Team
  |url        = https://ciclops.org/team/iss_team.php.html
  |work       = Cassini Imaging Central Laboratory for Operations
  |publisher  = NASA
  |access-date = 13 June 2023
  |url-status = live
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}}

== External links ==
{{commons|Polydeuces}}
* [https://solarsystem.nasa.gov/moons/saturn-moons/polydeuces/in-depth/ Polydeuces In Depth], NASA Solar System Exploration, updated 19 December 2019
* [https://photojournal.jpl.nasa.gov/catalog/?IDNumber=PIA08209 PIA08209: New Moon], NASA Photojournal, 28 June 2006
* [http://spaceflightnow.com/cassini/050224science.html Cassini finds treasures among Saturn's rings, moons], ''Cassini'' news release via ''Spaceflight Now'', 24 February 2005

{{Moons of Saturn|state=uncollapsed}}
{{Saturn}}
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{{DEFAULTSORT:Polydeuces (Moon)}}
[[Category:Moons of Saturn]]
[[Category:Trojan moons]]
[[Category:Astronomical objects discovered in 2004|20041021]]
[[Category:Moons with a prograde orbit]]
[[Category:Castor and Pollux]]