Editing Saturn (section)

== Orbit and rotation ==
[[File:Solar system orrery outer planets.gif|thumb|Animation of Saturn and the Solar System's [[outer planet]]s orbiting around the Sun]]
[[File:Saturnoppositions-animated.gif|thumb|Simulated appearance of Saturn as seen from Earth (at [[Opposition (astronomy)|opposition]]) during an orbit of Saturn, 2001–2029]]

The average distance between Saturn and the Sun is over 1.4&nbsp;billion kilometers (9&nbsp;[[astronomical unit|AU]]). With an average orbital speed of 9.68&nbsp;km/s,<ref name="fact" /> it takes Saturn 10,759 Earth days (or about {{frac|29|1|2}}&nbsp;years)<ref name="cain2009" /> to finish one revolution around the Sun.<ref name="fact" /> As a consequence, it forms a near 5:2 [[mean-motion resonance]] with Jupiter.<ref>{{cite journal |title=Modeling the 5 : 2 Mean-Motion Resonance in the Jupiter-Saturn Planetary System |last1=Michtchenko |first1=T. A. |last2=Ferraz-Mello |first2=S. |journal=Icarus |volume=149 |issue=2 |pages=357–374 |date=February 2001 |doi=10.1006/icar.2000.6539 |bibcode=2001Icar..149..357M}}</ref> The elliptical orbit of Saturn is inclined 2.48° relative to the [[orbital plane]] of the Earth.<ref name="fact" /> The [[apsis|perihelion and aphelion]] distances are, respectively, 9.195 and 9.957&nbsp;AU, on average.<ref name="fact" /><ref>Jean Meeus, ''Astronomical Algorithms'' (Richmond, VA: Willmann-Bell, 1998). Average of the nine extremes on p 273. All are within 0.02&nbsp;AU of the averages.</ref> The visible features on Saturn rotate at different rates depending on latitude, and multiple rotation periods have been assigned to various regions (as in Jupiter's case).

Astronomers use three different systems for specifying the rotation rate of Saturn. ''System&nbsp;I'' has a period of {{RA|10|14|00}} (844.3°/d) and encompasses the Equatorial Zone, the South Equatorial Belt, and the North Equatorial Belt. The polar regions are considered to have rotation rates similar to ''System&nbsp;I''. All other Saturnian latitudes, excluding the north and south polar regions, are indicated as ''System&nbsp;II'' and have been assigned a rotation period of {{RA|10|38|25.4}} (810.76°/d). ''System&nbsp;III'' refers to Saturn's internal rotation rate. Based on [[radio astronomy|radio emissions]] from the planet detected by ''[[Voyager 1]]'' and ''Voyager 2'',<ref>{{cite journal|doi=10.1126/science.209.4462.1238|pmid=17811197|bibcode=1980Sci...209.1238K|title=Voyager Detection of Nonthermal Radio Emission from Saturn|journal=Science|volume=209|issue=4462|pages=1238–40|last1=Kaiser|first1=M. L.|last2=Desch|first2=M. D.|last3=Warwick|first3=J. W.|last4=Pearce|first4=J. B.|year=1980|hdl=2060/19800013712|s2cid=44313317|hdl-access=free}}</ref> System&nbsp;III has a rotation period of {{RA|10|39|22.4}} (810.8°/d). System&nbsp;III has largely superseded System&nbsp;II.<ref name=benton2006/>

A precise value for the rotation period of the interior remains elusive. While approaching Saturn in 2004, ''Cassini'' found that the radio rotation period of Saturn had increased appreciably, to approximately {{RA|10|45|45}} {{+-|{{RA|||36}}}}.<ref>{{cite web |url=http://www.nasa.gov/mission_pages/cassini/media/cassini-062804.html |title=Scientists Find That Saturn's Rotation Period is a Puzzle |date=28 June 2004 |publisher=NASA |access-date=22 March 2007 |archive-url=https://web.archive.org/web/20110729155336/http://www.nasa.gov/mission_pages/cassini/media/cassini-062804.html |archive-date=29 July 2011 |url-status=live }}</ref><ref name=cain2008_15298/> An estimate of Saturn's rotation (as an indicated rotation rate for Saturn as a whole) based on a compilation of various measurements from the ''Cassini'', ''Voyager'', and ''Pioneer'' probes is {{RA|10|32|35}}.<ref name=Anderson2007/> Studies of the planet's [[Rings of Saturn#C Ring|C Ring]] yield a rotation period of <span class="nowrap">{{RA|10|33|38}} {{+-|{{RA||1|52}}|{{RA||1|19}}}} </span>.<ref name="NASA-20190118" /><ref name="APJ-20190117" />

In March 2007, it was found that the variation in radio emissions from the planet did not match Saturn's rotation rate. This variance may be caused by geyser activity on Saturn's moon [[Enceladus]]. The water vapor emitted into Saturn's orbit by this activity becomes charged and creates a drag upon Saturn's magnetic field, slowing its rotation slightly relative to the rotation of the planet.<ref>{{cite press release |url=http://www.nasa.gov/mission_pages/cassini/media/cassini-20070322.html |title=Enceladus Geysers Mask the Length of Saturn's Day |date=22 March 2007 |publisher=NASA Jet Propulsion Laboratory |access-date=22 March 2007 |url-status=dead |archive-url=https://web.archive.org/web/20081207134416/http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=733 |archive-date=7 December 2008 }}</ref><ref name=science316_5823_442/><ref name=science316_5823_380/>

An apparent oddity for Saturn is that it does not have any known [[trojan asteroid]]s. These are minor planets that orbit the Sun at the stable [[Lagrangian point]]s, designated L<sub>4</sub> and L<sub>5</sub>, located at 60° angles to the planet along its orbit. Trojan asteroids have been discovered for [[Mars]], Jupiter, Uranus, and Neptune. [[Orbital resonance]] mechanisms, including [[secular resonance]], are believed to be the cause of the missing Saturnian trojans.<ref>{{cite journal |title=Saturn Trojans: a dynamical point of view |journal=Monthly Notices of the Royal Astronomical Society |display-authors=1 |last1=Hou |first1=X. Y. |last2=Scheeres |first2=D. J. |last3=Liu |first3=L. |volume=437 |issue=2 |pages=1420–1433 |date=January 2014 |doi=10.1093/mnras/stt1974 |bibcode=2014MNRAS.437.1420H|doi-access=free }}</ref>