Editing Neptune (section)

== Neptune's moons ==
{{mainarticle|List of Neptune's moons}}

Neptune has 16 known [[Natural satellite|moons]].<ref>{{cite web |url= https://www.bbc.co.uk/news/science-environment-23318301 |title=Nasa's Hubble telescope discovers new Neptune moon |publisher=BBC |date=July 15, 2013 |access-date=July 16, 2013}}</ref> As Neptune was the Roman god of the sea, the planet's moons were named after lesser sea gods or goddesses.<ref>[https://planetarynames.wr.usgs.gov/Page/Planets "Planet and Satellite Names and Discoverers"]. Gazetteer of Planetary Nomenclature. U.S. Geological Survey.</ref>

The largest moon of Neptune is [[Triton (moon)|Triton]]. Triton was discovered on October 10, 1846 by British astronomer [[William Lassell]].<ref>{{Cite web|title=In Depth {{!}} Triton|url=https://solarsystem.nasa.gov/moons/neptune-moons/triton/in-depth|access-date=June 13, 2021|website=NASA Solar System Exploration|archive-date=August 17, 2018|archive-url=https://web.archive.org/web/20180817014136/https://solarsystem.nasa.gov/moons/neptune-moons/triton/in-depth|url-status=dead}}</ref> Unlike all other large planetary moons, Triton [[Retrograde orbit|orbits in the other direction]] to the other moons.<ref name=":4" /> This shows the moon was probably captured.<ref name=":4">Agnor, Craig B.; Hamilton, Douglas P. 2006. Neptune's capture of its moon Triton in a binary–planet gravitational encounter. ''Nature'' '''441''' (7090): 192–194.</ref> It is close enough to Neptune to be locked into a [[synchronous orbit]]. It is also slowly moving into Neptune and may one day be torn apart when it passes the [[Roche limit]].<ref>{{Cite journal|last1=Jankowski| first1=David G.|last2=Chyba|first2=Christopher F.| last3=Nicholson|first3=Philip D.|year=1989|title=Tidal evolution in the Neptune-Triton system|journal=Astronomy and Astrophysics. |volume=219|issue=1–2|pages=L23–L26| bibcode=1989A&A...219L..23C}}</ref> Triton is the coldest object that has been measured in the Solar System, with temperatures of −235&nbsp;°C (38 K, −392&nbsp;°F).<ref>Nelson R.M; Smythe W.D; Wallis B.D; Horn L.J; et al 1990. Temperature and thermal emissivity of the surface of Neptune's satellite Triton. ''Science''. '''250''' (4979): 429–31.</ref>

Neptune's second known moon (by order of discovery), the odd moon [[Nereid (moon)|Nereid]], has one of the most unusual orbits of any satellite in the Solar System.<ref name=":19">{{Cite web|title=In Depth {{!}} Nereid|url=https://solarsystem.nasa.gov/moons/neptune-moons/nereid/in-depth|access-date=June 11, 2021|website=NASA Solar System Exploration|archive-date=June 11, 2021|archive-url=https://web.archive.org/web/20210611214602/https://solarsystem.nasa.gov/moons/neptune-moons/nereid/in-depth/|url-status=dead}}</ref> Nereid is so far from Neptune that it requires 360 Earth days to make one orbit.<ref name=":19" /> It causes the largest [[elliptical orbit]] and the largest deviation from a [[Circular orbit|circular path]].<ref name=":19" />

Some of these moons have been speculated to have been possible [[Kuiper belt|Kupier belt]] objects, which in turn became a part of Neptune's orbit.

From July to September 1989, ''Voyager 2'' discovered six new moons of Neptune.<ref>Stone, E.C.; Miner, E.D. (1989). "The Voyager 2 Encounter with the Neptunian System". ''Science''. 246 (4936): 1417–21.</ref> Of these, [[Proteus (moon)|Proteus]] is the second most massive Neptunian moon.<ref name=":17">{{Cite web|date=May 29, 2010|title=Planet Neptune's moons|url=https://www.newtimes.co.rw/section/read/81791|access-date=June 15, 2021|website=The New Times {{!}} Rwanda|language=en}}</ref> It has only one quarter of 1% of the mass of Triton.<ref name=":17" /> Neptune's closest four moons, [[Naiad (moon)|Naiad]], [[Thalassa (moon)|Thalassa]], [[Despina (moon)|Despina]], and [[Galatea (moon)|Galatea]], orbit close enough to be inside Neptune's rings. The next farthest out, [[Larissa (moon)|Larissa]] was discovered in 1981 when it had covered up light from a star.<ref>{{Cite web|title=In Depth {{!}} Larissa|url=https://solarsystem.nasa.gov/moons/neptune-moons/larissa/in-depth|access-date=June 15, 2021|website=NASA Solar System Exploration|archive-date=June 27, 2021|archive-url=https://web.archive.org/web/20210627110206/https://solarsystem.nasa.gov/moons/neptune-moons/larissa/in-depth/|url-status=dead}}</ref> The moon was credited for causing Neptune's ring arcs when ''Voyager 2'' observed Neptune in 1989. Five new unusual moons discovered between 2002 and 2003 were announced in 2004.<ref>{{cite journal |last=Holman|first=Matthew J. |date=August 19, 2004 |url=http://www.nature.com/nature/journal/v430/n7002/abs/nature02832.html |title=Discovery of five irregular moons of Neptune |journal=Nature |volume=430 |issue=7002 |pages=865–867|doi=10.1038/nature02832 |pmid=15318214 |bibcode=2004Natur.430..865H |s2cid=4412380 }}</ref><ref>{{cite news |url=http://news.bbc.co.uk/2/hi/science/nature/3578210.stm |title=Five new moons for planet Neptune |date=August 18, 2004 |work=BBC News |accessdate=August 6, 2007}}</ref> The latest moon, [[S/2004 N 1|Hippocamp]], was discovered from examining Hubble Telescope images on July 16, 2013.<ref>{{Cite news|date=July 15, 2013|title=Nasa's Hubble telescope discovers new Neptune moon|language=en-GB|work=BBC News|url=https://www.bbc.com/news/science-environment-23318301|access-date=June 13, 2021}}</ref>
[[File:Neptune_and_Triton_with_their_sizes_and_distance_from_each_other_to_scale.png|thumb|Neptune and Triton in true sizes and distances from each other]]
[[File:Neptune's Dynamic Environment.webm|thumb|A 15-hour time-lapse of Neptune in the [[Near infrared|near-infrared]] captured by [[Hubble Space Telescope|Hubble]]. [[Triton (moon)|Triton]] is clearly visible, while others appear much smaller.]]
{{multiple image
| align             = center
| direction         = horizontal
| header_align      = center
| header            = Moons
| image1            = Voyager 2 Neptune and Triton.jpg
| width1            = 220
| caption1          = Neptune (top) and Triton (bottom)
| image2            = Triton moon mosaic Voyager 2 (large).jpg
| width2            = 165
| caption2          = A ''Voyager 2'' mosaic of Triton
| image3            = Proteus (Voyager 2).jpg
| width3            = 165
| caption3          = Proteus
}}