Editing Iapetus (moon) (section)

==History==
=== Discovery ===
[[File:Giovanni Cassini.jpg|left|thumb|upright|Giovanni Domenico Cassini, discoverer of Iapetus]]
Iapetus was discovered by [[Giovanni Domenico Cassini]], an Italian-born French astronomer, in October 1671. This is the first moon that Cassini discovered; the second moon of Saturn to be discovered after [[Christiaan Huygens]] spotted [[Titan (moon)|Titan]] 16 years prior in 1655; and the sixth extraterrestrial moon to be discovered in human history.

Cassini discovered Iapetus when the moon was on the western side of Saturn, but when he tried viewing it on the eastern side some months later, he was unsuccessful. This was also the case the following year, when he was again able to observe it on the western side, but not the eastern side. Cassini finally observed Iapetus on the eastern side in 1705 with the help of an improved telescope, finding it two [[apparent magnitude|magnitudes]] dimmer on that side.<ref>{{cite book|last1=Van Helden|first1=Albert|title=Saturn through the telescope: A brief historical survey|location=[[Tucson, Arizona]]|bibcode=1984satn.book...23V|publisher=[[University of Arizona Press]]|pages=23–43|year=1984}}</ref><ref>{{cite book|last1=Harland|first1=David M.|author-link1=David M. Harland|title=Mission to Saturn: Cassini and the Huygens Probe|location=Chichester|publisher=[[Springer Publishing]]|isbn=978-1852336561|year=2002}}{{page needed|date=October 2022}}</ref>

Cassini correctly surmised that Iapetus has a bright hemisphere and a dark hemisphere, and that it is [[tidal locking|tidally locked]], always keeping the same face towards Saturn. This means that the bright hemisphere is visible from Earth when Iapetus is on the western side of Saturn, and that the dark hemisphere is visible when Iapetus is on the eastern side.<ref>{{cite book|title= Moons: A Very Short Introduction|first1=David A.|last1=Rotherty|publisher=[[Oxford University Press]]|date=January 1, 2016|isbn=9780198735274|page=102}}</ref>

=== Name ===
[[File:John_F._Hershel.png|left|thumb|upright|[[John Herschel]], the astronomer who suggested that the moons of Saturn be named after the Titans and Giants]]Iapetus is named after the [[Titans|Titan]] [[Iapetus]] from [[Greek mythology]]. The name was suggested by John Herschel (son of [[William Herschel]]) in his 1847 publication ''Results of Astronomical Observations made at the Cape of Good Hope'',<ref name="Lassell" /> in which he advocated naming the moons of Saturn after the Titans, brothers and sisters of the Titan [[Cronus]] (whom the [[Roman mythology|Romans]] equated with their god [[Saturn (mythology)|Saturn]]); and [[Giants (Greek mythology)|Giants]], the massive but lesser relatives of the Titans who sided with the Titans against [[Zeus]] and the [[Twelve Olympians|Olympian Gods]].<ref>https://library.si.edu/digital-library/book/resultsastronom00hers - Page 415</ref>

The name has a largely obsolete variant, '''Japetus'''<ref name="Lassell">{{cite journal | last = Lassell| first = William| date = January 14, 1848| title = Satellites of Saturn| journal = [[Monthly Notices of the Royal Astronomical Society]]| volume = 8| issue = 3| pages = 42–43| url = http://adsabs.harvard.edu//full/seri/MNRAS0008//0000042.000.html| bibcode = 1848MNRAS...8...42L|doi=10.1093/mnras/8.3.42 | doi-access = free}}</ref><ref name=Hill1952/> {{IPAc-en|ˈ|dʒ|æ|p|ᵻ|t|ə|s}},<ref>{{cite book|first1=Noah|last1=Webster|author-link=Noah Webster|date=1884|url=https://books.google.com/books?id=5YVDAQAAMAAJ|publisher=[[Merriam-Webster]]|editor=Dorsey Gardner|title=A Practical Dictionary of the English Language}}{{page needed|date=October 2022}}</ref>
with an adjectival form ''Japetian''.<ref name=Hill1952>George William Hill (1952) ''The Radiant Universe'', p. 280</ref>
These occurred because there was no distinction between the letters {{angbr|i}} and {{angbr|j}} in Latin, and authors rendered them differently.

When first discovered, Iapetus was among the four [[Moons of Saturn|Saturnian moons]] labelled the ''[[Sidera Lodoicea]]'' by their discoverer Giovanni Cassini after [[Louis XIV of France|King Louis XIV]] (the other three were [[Tethys (moon)|Tethys]], [[Dione (moon)|Dione]] and [[Rhea (moon)|Rhea]]). However, astronomers fell into the habit of referring to them using Roman numerals, with Iapetus being '''Saturn V''' because it was the fifth known Saturnian moon in order of distance from Saturn at that time. Once [[Mimas (moon)|Mimas]] and [[Enceladus (moon)|Enceladus]] were discovered in 1789, the numbering scheme was extended and Iapetus became '''Saturn&nbsp;VII'''. With the discovery of [[Hyperion (moon)|Hyperion]] in 1848, Iapetus became '''Saturn VIII''', which is still its Roman numerical designation today.<ref name=NASADepth>{{cite web|url=https://solarsystem.nasa.gov/moons/saturn-moons/iapetus/in-depth/|title=Iapetus: In Depth|last1=Davis|first1=Phil|last2=Dunford|first2=Bill|last3=Boeck|first3=Moore|website=Solar System Exploration: Our Galactic Neighbourhood|publisher=[[NASA]]|date=December 19, 2019|accessdate=March 1, 2023}}</ref> Geological features on Iapetus are generally named after characters and places from the [[Chanson de geste|French epic poem]] ''[[The Song of Roland]]''.<ref name=NASADepth/>

Planetary moons other than Earth's were never given symbols in the astronomical literature. Denis Moskowitz, a software engineer who designed most of the [[dwarf planet]] symbols, proposed a Greek [[iota]] (the initial of Iapetus) combined with the crook of the Saturn symbol as the symbol of Iapetus ([[File:Iapetus symbol (fixed width).svg|16px]]). This symbol is not widely used.<ref name=moons>{{cite web |url=https://www.unicode.org/L2/L2025/25079-phobos-and-deimos.pdf |title=Phobos and Deimos symbols |last1=Bala |first1=Gavin Jared |last2=Miller |first2=Kirk |date=7 March 2025 |website=unicode.org |publisher=The Unicode Consortium |access-date=14 March 2025 |quote=}}</ref>