Editing Saturn (section)

== Planetary rings ==
{{Main|Rings of Saturn}}
Saturn is best known for its [[planetary rings]], which are easy to see with a [[telescope]]. There are seven named rings: A, B, C, D, E, F, and G.<ref name=cosmos>{{cite journal 
 |last=Lovett |first=Rick
 |date= June 2011 |title=Dance of the rings
 |journal=Cosmos |issue=39 |pages=57
 |url=http://www.cosmosmagazine.com/ |access-date= June 21, 2011}}</ref> They were named in the order they were found, which is different to their order from the planet. From the planet, the rings are ordered: D, C, B, A, F, G and E.<ref name=cosmos />{{rp|57}}

Some scientists think that the rings are [[material]] left after a moon broke apart.<ref name=cosmos />{{rp|60}} A newer idea is that it was a very large moon, most of which crashed into the planet. This would have left a large amount of ice to form the rings and some of the moons, including [[Enceladus (moon)|Enceladus]], which is made of ice.<ref name=cosmos />{{rp|61}}

=== History ===
The rings were first found by [[Galileo Galilei]] in 1610, using his telescope. They did not look like rings to Galileo. He called them "handles". He thought that Saturn was three different planets that were right next to each other. In 1612, when the rings were facing edge on with the Earth, the rings disappeared, then reappeared again in 1613, further confusing Galileo.<ref name="history_of_the_rings">{{cite web |url=http://www2.jpl.nasa.gov/saturn/back.html |title=Historical background of Saturn's rings |first=Ron |last=Baalke |work=www2.jpl.nasa.gov |publisher=National Aeronautics and Space Administration |year=2005 |access-date=July 6, 2011 |archive-date=March 21, 2009 |archive-url=https://web.archive.org/web/20090321071339/http://www2.jpl.nasa.gov/saturn/back.html |url-status=dead }}</ref> In 1655, [[Christiaan Huygens]] was the first person to say that Saturn was surrounded by rings. Using a much more powerful telescope than Galileo's, he said that Saturn "is surrounded by a thin, flat, ring, nowhere touching...".<ref name="history_of_the_rings" /> In 1675, [[Giovanni Domenico Cassini]] found that the planet's rings were in fact made of smaller rings with gaps. The largest ring gap was later named the [[Rings of Saturn|Cassini Division]]. In 1859, [[James Clerk Maxwell]] showed that the rings are made of small bits or particles, each orbiting Saturn on their own. He found that if the rings were solid, they would become unstable or break apart.<ref>{{cite web |url=http://www-history.mcs.st-andrews.ac.uk/~history/Extras/Maxwell_Saturn.html |title=James Clerk Maxwell on the nature of Saturn's rings |first=James Clerk |last=Maxwell |work=www-history.mcs.st-andrews.ac.uk |year=1859 |access-date=June 19, 2011}}</ref> [[James Keeler]] studied the rings using a [[spectrometer|spectroscope]] in 1895, which proved Maxwell right.<ref>{{cite web |url=http://www.sil.si.edu/DigitalCollections/HST/Huygens/huygens-introduction.htm |title=Christiaan Huygens and his Systema Saturnium |author=Brashear, Ronald |date=May 1999 |publisher= [[Smithsonian Institution]] Libraries|access-date=April 19, 2011}}</ref>

=== Physical features ===
The rings are found between {{convert|6630|km|mi|0|lk=off|abbr=on}} to {{convert|120700|km|mi|0|lk=off|abbr=on}} above the planet's equator. The [[circumference]] of Saturn at its [[equator]] is 378,675 km (235,298 miles). As found by Maxwell, even though the rings look solid and unbroken when viewed from above, the rings are made of small particles of rock and ice. The particles are only about {{convert|10|m|ft|0|lk=off|abbr=on}} thick; made of [[silicon dioxide|silica]] rock, [[iron oxide]] and ice particles.<ref name=cosmos />{{rp|55}} The smallest particles are only specks of dust, while the largest are the size of a house. The C and D rings also seem to have a "wave" in them, like waves in water.<ref name=cosmos />{{rp|58}} These large waves are {{convert|500|m|ft|0|lk=off|abbr=on}} high, but they move slowly, at about {{convert|250|m|ft|0|lk=off|abbr=on}} each day on Saturn.<ref name=cosmos />{{rp|58}} Some scientists believe that the waves are caused by Saturn's moons.<ref>{{cite web |url=http://solarsystem.nasa.gov/planets/profile.cfm?Object=Saturn&Display=Rings |title=Saturn: Rings |work=Solar System exploration| publisher=National Aeronautics and Space Administration |date=March 22, 2011 |access-date=June 19, 2011}}</ref> Another idea is the waves were made by a [[comet]] hitting Saturn.<ref name=cosmos />{{rp|60}}

The largest gaps in the rings are the Cassini Division and the [[Rings of Saturn|Encke Division]] which are both visible from Earth. The Cassini Division is the largest of Saturn's ring gaps at {{convert|4800|km|mi|0|lk=off|abbr=on}} wide.<ref name="Cassini_Division">{{cite web |url=http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level2/cassini_division.html |title=StarChild: Saturn's Cassini Division |work=The Solar System| publisher= National Aeronautics and Space Administration |year=2011 |access-date=June 19, 2011}}</ref> When the [[Voyager program|Voyager]] spacecrafts visited Saturn in 1980, they discovered that the rings are in a complex structure made out of thousands of thin gaps and smaller rings. Scientists believe this is caused by the [[gravity|gravitational force]] of some of Saturn's moons. The tiny moon [[Pan (moon)|Pan]] orbits inside Saturn's rings, creating a gap within the rings. Other ringlets keep their structure due to the gravity of [[shepherd satellite]]s, such as [[Prometheus (moon)|Prometheus]] and [[Pandora (moon)|Pandora]]. Other gaps form due to the gravity of a large moon farther away. The moon [[Mimas (moon)|Mimas]] is what made the Cassini Division.<ref name="Cassini_Division" />

[[Data]] from the Cassini spacecraft has shown that the rings have their own [[atmosphere]], free from the planet's atmosphere. The rings' atmospheres have oxygen and hydrogen gas. The oxygen gas is made when the Sun's [[ultraviolet]] light breaks up the water ice in the rings. [[Chemical reaction|Chemical reactions]] also occur between the ultraviolet light and the water [[molecule]]s, creating hydrogen gas. The oxygen and hydrogen atmospheres around the rings are very widely spaced.<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/science/nature/4640641.stm |title=Saturn rings have own atmosphere |first=Paul |last=Rincon |work=[[BBC News]] |date=July 1, 2005 |publisher=[[BBC]] |location=London |access-date=June 19, 2011}}</ref> As well as oxygen and hydrogen gas, the rings have a thin atmosphere made of [[hydroxide]] (a combination of oxygen and hydrogen), which was discovered by the [[Hubble Space Telescope]].<ref>{{cite journal |url=http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2006ApJ...644L.137J&amp;db_key=AST&amp;data_type=HTML&amp;format=&amp;high=42bf06f4d906731%20The%20Enceladus%20and%20OH%20Tori%20at%20Saturn |title=The Enceladus and OH Tori at Saturn |first= R.E.|last=Johnson |journal=SAO/NASA ADS Astronomy Abstract Service |year=2006 |volume=644 |issue=2 |pages=L137–L139 |doi=10.1086/505750 |bibcode=2006ApJ...644L.137J |s2cid=37698445 |access-date=June 19, 2011}}</ref>

=== Spokes ===
[[File:Voyager 2 - Saturn Rings - 3085 7800 2.png|thumb|right|alt=The spokes in Saturn's rings|The spokes in Saturn's rings, photographed by Voyager 2]]

The Voyager [[space probe]] discovered features shaped like [[ray]]s, called spokes.<ref name=malik>{{cite web |url=http://www.space.com/1554-cassini-probe-spies-spokes-saturn-rings.html |title=Cassini Probe spies spokes in Saturn's rings |first=Tariq |last=Malik |work=space.com |date=September 15, 2005 |access-date=April 26, 2011}}</ref> These were seen later by the Hubble telescope. The Cassini-Huygens probe [[photograph]]ed the spokes in 2005.<ref name=malik /> They appear dark when lit by sunlight, and appear light against the dark side of the planet. At first it was thought the spokes were made of microscopic dust particles, but new evidence shows that they are made of ice.<ref>{{cite web |url=http://www.nasa.gov/mission_pages/cassini/media/cassini-070204.html |title=Cassini exposes puzzles about ingredients in Saturn's rings |work=Cassini: unlocking Saturn's secrets |publisher=National Aeronautics and Space Administration |date=June 2, 2009 |access-date=May 24, 2011 |archive-date=December 24, 2010 |archive-url=https://web.archive.org/web/20101224112125/http://www.nasa.gov/mission_pages/cassini/media/cassini-070204.html |url-status=dead }}</ref>
They rotate at the same rate as the planet's [[magnetosphere]], therefore, it is believed that they have a connection with [[electromagnetism]]. However, what causes the spokes to form is still unknown. They appear to be [[season]]al, disappearing during the [[solstice|solstices]] and appearing again during [[equinox|equinoxes]].<ref>{{cite web |url=http://apod.nasa.gov/apod/ap090602.html |title=Spoke's reappear on Saturn's rings |work=Astronomy Picture Of The Day| publisher=National Aeronautics and Space Administration |date=June 2, 2009 |access-date=April 26, 2011}}</ref>