View source for Nix (moon)

{{Short description|Moon of Pluto}}
{{About-distinguish2|the moon of Pluto|the asteroid [[3908 Nyx]]}}
{{good article}}
{{use dmy dates|date=July 2023}}
{{Infobox planet
 | name            = Nix
 | image           = Nix best view.jpg
 | caption         = Enhanced color image of Nix, taken by ''[[New Horizons]]''
 | discovery_ref   = <ref name="Nomenclature">{{cite web|title=Planet and Satellite Names and Discoverers|website=Gazetteer of Planetary Nomenclature|publisher=International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (WGPSN)|url=https://planetarynames.wr.usgs.gov/Page/Planets|access-date=17 May 2021}}</ref>
 | discoverer      = [[Hal A. Weaver]] et al.{{efn|The full list of discoverers includes [[Hal A. Weaver|H. A. Weaver]], [[S. Alan Stern|S. A. Stern]], M. J. Mutchler, A. J. Steffl, [[Marc W. Buie|M. W. Buie]], W. J. Merline, J. R. Spencer, E. F. Young, and L. A. Young.<ref name="Nomenclature"/>}}
 | discovered      = 15 May 2005
 | alt_names       = S/2005 P 2
 | mpc_name        = Pluto II<ref name="Nomenclature" />
 | named_after     = [[Nyx (mythology)|Nyx]]
 | pronounced      = {{IPAc-en|ˈ|n|ɪ|k|s}}
 | adjectives      = Nictian ({{IPAc-en|ˈ|n|ɪ|k|t|i|ən}})
 | orbit_ref       = <ref name="ShowalterHamilton2015">{{cite journal|last1=Showalter|first1=M. R.|author1-link=Mark R. Showalter|last2=Hamilton|first2=D. P.|title=Resonant interactions and chaotic rotation of Pluto's small moons|journal=Nature|volume=522|issue=7554|date=3 June 2015|pages=45–49|doi=10.1038/nature14469|pmid=26040889|bibcode=2015Natur.522...45S|s2cid=205243819}}</ref>
 | semimajor       = {{val|48694|3|u=km}}
 | eccentricity    = {{val|0.002036|0.000050}}
 | period          = {{val|24.85463|0.00003|u=d}}
 | inclination     = {{val|0.133|0.008|u=°}} ({{val|122.53|0.008|u=°}} to Pluto's orbit)
 | satellite_of    = [[Pluto]]
 | dimensions      = {{nowrap|1=49.8 × 33.2 × 31.1 km}}<ref name="phasecurves" /><br/>([[Geometric mean]] of 37 km)
 | volume          = 
 | mass            = {{val|2.60|0.52|e=16|u=kg}}<ref name="Porter2023"/>{{rp|page=10}}
 | density         = {{val|1.031|0.204|u=g/cm3}}<ref name="Porter2023"/>{{rp|page=10}}
 | surface_grav    = ≈&thinsp;{{Gr|2.6e-5|24.9|4}}&nbsp;m/s<sup>2</sup> at longest axis<br/>to ≈&thinsp;{{Gr|2.6e-5|15.55|4}}&nbsp;m/s<sup>2</sup> at poles
 | escape_velocity = ≈&thinsp;{{V2|2.6e-5|24.9|4}}&nbsp;km/s at longest axis<br/>to ≈&thinsp;{{V2|2.6e-5|15.55|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 -->
 | rotation        = {{val|1.829|0.009|u=d}}<ref name="Weaver2016"/>{{rp|page=3}}
chaotic<ref>{{cite web|url=http://www.nasa.gov/press-release/nasa-s-hubble-finds-pluto-s-moons-tumbling-in-absolute-chaos|title=NASA's Hubble Finds Pluto's Moons Tumbling in Absolute Chaos|first=Karen|last=Northon|date=3 June 2015}}</ref> (decreased by 10% between discovery and flyby)<ref name=Lakdawalla1110>{{cite web|url=http://www.planetary.org/blogs/emily-lakdawalla/2015/dps15-1110-small-moons.html|title=DPS 2015: Pluto's small moons Styx, Nix, Kerberos, and Hydra [UPDATED]|website=www.planetary.org|last1=Lakdawalla|first1=Emily|access-date=2015-11-14|archive-date=2017-09-27|archive-url=https://web.archive.org/web/20170927202313/http://www.planetary.org/blogs/emily-lakdawalla/2015/dps15-1110-small-moons.html|url-status=dead}}</ref>
 | axial_tilt      = {{val|123|10|u=°}} (to Pluto–Charon orbit)<ref name="Weaver2016-supp"/>{{rp|page=11}}<br/>{{val|48|10|u=°}} (to [[celestial equator]]){{efn|name=axial-tilt|Given Nix's rotational north pole [[declination]] of +42°,<ref name="Weaver2016"/>{{rp|page=5}} subtracting this angle from the north [[celestial pole]] of +90° gives the inclination with respect to the [[celestial equator]]: ''i'' {{=}} +90° – (+42°) {{=}} +48°.}}
 | right_asc_north_pole = {{val|350|10|u=°}}<ref name="Weaver2016"/>{{rp|page=3}}
 | declination     = {{val|42|10|u=°}}<ref name="Weaver2016"/>{{rp|page=3}}
 | albedo          = {{val|0.56|0.05}}<ref name="Weaver2016"/>{{rp|page=3}}
 | magnitude       = 23.38–23.7 (measured)<ref name="Stern06b" />
 | abs_magnitude   = 8.28<ref name="Weaver2016"/>{{rp|page=2}}
 | single_temperature = 
}}

'''Nix''', formal designation '''(134340) Pluto II''',  is a [[Moons of Pluto|natural satellite of Pluto]], with a diameter of {{convert|49.8|km|mi|abbr=on}} across its longest dimension.<ref name="phasecurves" /> It was discovered along with Pluto's outermost moon [[Hydra (moon)|Hydra]] on 15 May 2005 by astronomers using the [[Hubble Space Telescope]],<ref name="Nomenclature" /> and was named after [[Nyx (mythology)|Nyx]], the Greek goddess of the night.<ref name="plutomoons" /> Nix is the third moon of [[Pluto]] by distance, orbiting between the moons [[Styx (moon)|Styx]] and [[Kerberos (moon)|Kerberos]].<ref name="scimag000" />

Nix was imaged along with [[Pluto]] and its other moons by the ''[[New Horizons]]'' spacecraft as it flew by the Pluto system in July&nbsp;2015.<ref name="UniverseToday">{{cite web|title=Pluto's Moon Nix|author=Cain, Fraser|date=3 September 2015|url=http://www.universetoday.com/13905/plutos-moon-nix/|website=www.universetoday.com|access-date=26 February 2019}}</ref> These images reveal a large reddish area on Nix that is likely an [[impact crater]].<ref name="SimonPort2015" />

== Discovery ==
[[File:Pluto system 2005 discovery images.jpg|thumb|left|Discovery images of Nix and Hydra]]

Nix was independently discovered by Max Mutchler and Andrew Steffl, members of the Pluto Companion Search Team, using the [[Hubble Space Telescope]].<ref name="plutomoons">{{Cite web|title = Pluto and Its Moons: Charon, Nix and Hydra|url = https://www.nasa.gov/mission_pages/hubble/plutos_moons.html|website = www.nasa.gov|publisher = NASA|date = 23 June 2006|access-date = 23 February 2019|archive-date = 21 May 2022|archive-url = https://web.archive.org/web/20220521001103/https://www.nasa.gov/mission_pages/hubble/plutos_moons.html|url-status = dead}}</ref> The ''New Horizons'' team had suspected that Pluto and its moon [[Charon (moon)|Charon]] might be accompanied by other moons, hence they used Hubble to search for faint moons around Pluto in 2005.<ref name="ChasingNH" /> Since Nix's brightness is about 5,000 times fainter than Pluto, long exposure images were taken in order to find it.<ref name="indepth">{{Cite web|title = Nix In Depth|url = https://solarsystem.nasa.gov/moons/pluto-moons/nix/in-depth/|website = solarsystem.nasa.gov|access-date = 23 February 2019}}</ref>

The discovery images were taken on 15&nbsp;May 2005 and 18&nbsp;May 2005. The discoveries were announced on 31&nbsp;October 2005, after confirmation by [[precovery|precovering]] archival Hubble images of Pluto from 2002.<ref name="hubblesite">{{cite web|url=http://hubblesite.org/news_release/news/2005-19|title=NASA's Hubble Reveals Possible New Moons Around Pluto|date=31 October 2005|website=www.hubblesite.org}}</ref> The two newly announced moons of Pluto were subsequently [[provisional designation in astronomy|provisionally designated]] S/2005 P 1 for Hydra and '''S/2005 P 2''' for Nix. The moons were informally referred to as "P1" and "P2", respectively by the discovery team.<ref name="IAUC8625">{{cite web|url=http://www.cbat.eps.harvard.edu/iauc/08600/08625.html|title=IAU Circular No. 8625|date=31 October 2005|website=www.cbat.eps.harvard.edu}} describing the discovery</ref>

== Naming ==
[[File:Pluto and its satellites (2005).jpg|thumb|left|Hubble image of Pluto's moons (annotated)]]

The name Nix was approved by the [[International Astronomical Union]] (IAU) and was announced on 21 June 2006 along with the naming of Hydra in the IAU Circular 8723.<ref name="IAUC8723">[http://www.cbat.eps.harvard.edu/iauc/08700/08723.html IAU Circular No. 8723] naming the moons.</ref> Nix was named after [[Nyx]], the Greek goddess of darkness and night and mother of [[Charon]], the ferryman of [[Hades]] in [[Greek mythology]]. The two newly named moons were intentionally named that the order of their initials ''N'' and ''H'' honors the ''New Horizons'' mission to Pluto, similarly to how the first two letters of Pluto's name honors [[Percival Lowell]].<ref name="UniverseToday2006">{{cite web|title=Pluto's New Moons are Named Nix and Hydra|author=Cain, Fraser | date=2006 | url= https://www.universetoday.com/152/plutos-new-moons-are-named-nix-and-hydra/|website=www.universetoday.com|access-date= 23 February 2019}}</ref><ref name="ChasingNH">{{cite book |last1=Stern |first1=Alan |last2=Grinspoon |first2=David |title=[[Chasing New Horizons]]: Inside the Epic First Mission to Pluto |publisher=Picador |date=May 1, 2018 |chapter=Chapter 7: Bringing It All Together |isbn=978-1-250-09896-2}}</ref> The original proposal for the naming of Nix was to use the [[Ancient Greek|classical]] spelling Nyx, but to avoid confusion with the [[asteroid]] [[3908 Nyx]], the spelling was changed to Nix, the [[Coptic language|Coptic]] spelling of the name.<ref name="UniverseToday2006" /> The adjectival form of the name is Nictian (cf. Russian Никта ''Nikta'').

The names of features on the bodies in the Pluto system are related to mythology and the literature and history of exploration. In particular, the names of features on Nix must be related to deities of the night from literature, mythology, and history.<ref name="nomenclature" />

== Origin ==

Pluto's smaller moons, including Nix, were thought to have formed from [[Collisional family|debris ejected from a massive collision]] between Pluto and another [[Kuiper belt]] object, similarly to how the [[Moon]] is believed to have formed from debris ejected by a [[giant-impact hypothesis|large collision of Earth]].<ref name="SternFormation">{{Cite journal | last = Stern | first = S. A. | author-link = Alan Stern | author2 = Weaver, H. A. | author3 = Steff, A. J. | author4 = Mutchler, M. J. | author5 = Merline, W. J. | author6 = Buie, M. W. | author7 = Young, E. F. | author8 = Young, L. A. | author9 = Spencer, J. R. | title = A giant impact origin for Pluto's small moons and satellite multiplicity in the Kuiper belt | journal = [[Nature (journal)|Nature]] | volume = 439 | issue = 7079 | pages = 946–948 | date = 23 February 2006 | url = http://ns1.plutoportal.net/~layoung/eprint/Stern2006plutosat.pdf | doi = 10.1038/nature04548 | access-date = 20 July 2011 | bibcode = 2006Natur.439..946S | pmid = 16495992 | s2cid = 4400037 | url-status = dead | archive-url = https://web.archive.org/web/20120119001455/http://ns1.plutoportal.net/~layoung/eprint/Stern2006plutosat.pdf | archive-date = 19 January 2012 }}</ref> The ejecta from the collision would then have coalesced into the moons of Pluto.<ref name="chaos" /> However, the collisional hypothesis cannot explain how Nix maintained its highly reflective surface.<ref name="DPS15" />

== Physical characteristics ==

Nix has an elongated shape, with its longest axis measured at {{convert|49.8|km|mi|abbr=on}} across and its shortest axis {{convert|31.1|km|mi|abbr=on}} across. This gives Nix the measured dimensions of {{convert|49.8|×|33.2|x|31.1|km|mi|abbr=on}}.<ref name="phasecurves" /> It is the third-largest moon of Pluto, being slightly smaller than [[Hydra (moon)|Hydra]].

Early research appeared to show that the surface of Nix is reddish in color.<ref name="Buie_2006" /> Contrary to this, other studies show that Nix is spectrally neutral, similar to the small moons of Pluto.<ref name="Stern06b">{{cite journal |last1=Stern |first1=S. A. |last2=Mutchler |first2=M. J. |last3=Weaver |first3=H. A. |last4=Steffl |first4=A. J. |title=The Positions, Colors, and Photometric Variability of Pluto's Small Satellites from HST Observations 2005–2006 |journal=Astronomical Journal |date=2006 |volume=132 |issue=3 |doi=10.1086/506347 |bibcode=2006AJ....132.1405S |arxiv = astro-ph/0605014 |pages=1405–1414|s2cid=14360964 }}</ref><ref name="Weaver2016" /> The neutral spectrum of Nix signifies that water ice is present on its surface.<ref name="DPS15" /> Nix also appeared to vary in brightness and [[albedo]], or reflectivity.<ref name="Stern06b" /> The brightness fluctuations were thought to be caused by areas with different albedos on the surface of Nix.<ref name="Stern06b" /> Images of Nix from the ''New Horizons'' spacecraft show a large reddish area approximately {{convert|18|km|mi|abbr=on}} across, which could explain the two conflicting measurements of Nix's surface color.<ref name="UniverseToday" /><ref name="nasa.gov">{{cite web|title=New Horizons Captures Two of Pluto's Smaller Moons|url=http://www.nasa.gov/image-feature/new-horizons-captures-two-of-plutos-smaller-moons/|publisher=NASA|date=21 July 2015}}</ref>

The reddish area is thought to be a large impact crater where the reddish material was ejected from underneath Nix's water ice layer and deposited on its surface.<ref name="SimonPort2015">{{cite web|last1=Porter|first1=Simon|title=Pluto's Small Moons Nix and Hydra|url=https://blogs.nasa.gov/pluto/2015/10/05/plutos-small-moons-nix-and-hydra/|website=blogs.nasa.gov|date=5 October 2015 |access-date=23 February 2019}}</ref> In this case, Nix would likely have [[regolith]]s originating from the impact.<ref name="Weaver2016" /> Another explanation suggests that the reddish material may have originated from a collision with Nix and another object with a different composition. However, there were no significant color variations on other impact craters on Nix.<ref name="Weaver2016" />

[[File:Simulation of Nix Rotation.ogg|thumb|Simulation of Nix, modelled as an [[ellipsoid]], showing its [[chaotic rotation]]]]
The water ice present on the surface of Nix is responsible for its high reflectivity.<ref name="UniverseToday" /><ref name="DPS15" /> Trace amounts of frozen [[methane]] may be also present on the surface of Nix, and could be responsible for the presence of reddish material, likely [[tholin]]s, on its surface.<ref name="UniverseToday" /> In this case, tholins on the surface of Nix may have originated from the reaction of methane with [[ultraviolet]] radiation from the [[Sun]].<ref name="UniverseToday" /> Derived from crater counting data from ''New Horizons'', the age of Nix's surface is estimated to be at least four billion years old.<ref name="arxiv1803">{{cite arXiv |last1=Woo |first1=M. Y. |last2=Lee |first2=M. H. |title=On the Early In Situ Formation of Pluto's Small Satellites |date=6 March 2018|eprint= 1803.02005|class=astro-ph.EP }}</ref><ref name="Weaver2016"/>

=== Rotation ===
[[File:A day on Nix.png|thumb|Six images of Nix taken by the New Horizons in July 2015 (contrast enhanced)]]
Nix is not [[Tidal locking|tidally locked]] and [[Chaotic rotation|tumbles chaotically]] similarly to all smaller moons of Pluto; the moon's axial tilt and rotation period vary greatly over short timescales.<ref name="chaos">{{Cite web|title = NASA's Hubble Finds Pluto's Moons Tumbling in Absolute Chaos|url = https://www.nasa.gov/press-release/nasa-s-hubble-finds-pluto-s-moons-tumbling-in-absolute-chaos|website = NASA|date = 3 June 2015|access-date = 25 October 2015|first = Karen|last = Northon}}</ref> Due to the [[chaotic rotation]] of Nix, it can occasionally flip its entire [[Rotation around a fixed axis|rotational axis]].<ref name="NYT2015">{{cite web|last1=Chang|first1=Kenneth|title=Astronomers Describe the Chaotic Dance of Pluto's Moons|url=https://www.nytimes.com/2015/06/04/science/space/pluto-moons-orbits-described-in-nature-article.html|work=The New York Times|date=3 June 2015|access-date=28 February 2019}}</ref> The varying gravitational influences of Pluto and Charon as they orbit their [[barycenter]] causes the chaotic tumbling of Pluto's small moons, including Nix.<ref name="chaos" /> The chaotic tumbling of Nix is also strengthened by its elongated shape, which creates [[torque]]s that act on the object.<ref name="chaos" /><ref name="ShowalterHamilton2015" /> At the time of the ''New Horizons'' flyby, Nix was rotating with a period of 43.9 hours retrograde to Pluto's equator with an [[axial tilt]] of 132 degrees —  it was rotating backwards in relation to its orbit around Pluto.<ref name="DPS15">{{cite web|last1=Lakdawalla|first1=Emily|title=DPS 2015: Pluto's small moons Styx, Nix, Kerberos, and Hydra|url=http://www.planetary.org/blogs/emily-lakdawalla/2015/dps15-1110-small-moons.html|website=The Planetary Society|access-date=14 November 2015|archive-date=27 September 2017|archive-url=https://web.archive.org/web/20170927202313/http://www.planetary.org/blogs/emily-lakdawalla/2015/dps15-1110-small-moons.html|url-status=dead}}</ref> The rotation rate of Nix had increased by 10 percent since Nix was discovered.<ref name="DPS15" />

== Orbit ==
{{multiple image | align = right | direction = horizontal | width = 
| header = Animation of moons of Pluto around the [[barycenter]] of Pluto – [[Ecliptic]] plane
| image1 = Animation of moons of Pluto - Front view.gif
| caption1 = Front view
| image2 = Animation of moons of Pluto - Side view.gif
| caption2 = Side view
| footer ={{legend2|khaki| [[Pluto]]}}{{·}}{{legend2|RoyalBlue| [[Charon (moon)|Charon]]}}{{·}}{{legend2|Lime| [[Styx (moon)|Styx]]}}{{·}}{{legend2|Magenta| Nix}}{{·}}{{legend2|Cyan| [[Kerberos (moon)|Kerberos]]}}{{·}}{{legend2|Orangered| [[Hydra (moon)|Hydra]]}}
}}

Nix orbits the Pluto-Charon [[barycenter]] at a distance of {{convert|48694|km|mi|abbr=on}}, between the orbits of [[Styx (moon)|Styx]] and [[Kerberos (moon)|Kerberos]].<ref name="scimag000" /> All of Pluto's moons including Nix have very circular orbits that are [[Coplanarity|coplanar]] to Charon's orbit; the moons of Pluto have very low [[orbital inclination]]s to Pluto's equator.<ref name="arxiv0511837" /><ref name="arxiv0802.2951" /> The nearly circular and coplanar orbits of Pluto's moons suggest that they may have gone through tidal evolutions since their formation.<ref name="arxiv0511837" /> At the time of the formation of Pluto's smaller moons, Nix may have had a more [[Orbital eccentricity|eccentric]] orbit around the Pluto-Charon barycenter.<ref name="tidaldamping" /> The present circular orbit of Nix may have been caused by Charon's tidal damping of the eccentricity of Nix's orbit, through tidal interactions. The mutual tidal interactions of Charon on Nix's orbit would cause Nix to transfer its orbital eccentricity to Charon, thus causing the orbit of Nix to gradually become more circular over time.<ref name="tidaldamping" />

Nix has an orbital period of 24.8546 days and its orbit is resonant with other moons of Pluto.<ref name="ShowalterHamilton2015" /> Nix is in a 3:2 [[orbital resonance]] with Hydra, and a 9:11 resonance with Styx (the ratios represent numbers of orbits completed per unit time; the period ratios are the inverses).<ref name="ShowalterHamilton2015" /><ref name="Witze2015">{{cite journal|last1=Witze|first1=Alexandra|title=Pluto's moons move in synchrony|journal=Nature|year=2015|doi=10.1038/nature.2015.17681|s2cid=134519717}}</ref> As a result of this "Laplace-like" 3-body resonance, it has conjunctions with Styx and Hydra in a 2:3 ratio.

Nix's orbital period is close to a 1:4 orbital resonance with Charon, with a timing discrepancy of 2.8%; there is no active resonance.<ref name="ShowalterHamilton2015" /><ref name="Buie_2006" /> A hypothesis explaining such a near-resonance is that the resonances originated before the outward migration of Charon following the formation of all five known moons, and is maintained by the periodic local fluctuation of 9 percent in the Pluto–Charon gravitational field strength.{{efn | The instantaneous force in the Pluto–Charon–Nix alignment case is 9.46% larger than in the quadrature case (where Nix is 90° from the Pluto–Charon axis); the Charon–Pluto–Nix case is almost exactly halfway between these values. In Buie ''et al.'', the quote is "The gravitational force exerted by Pluto on either P1 or P2 varies by roughly 15% (peak-to-peak)." Pluto's gravitational pull, ''by itself'', varies by 18% for Nix and 13% for Hydra.}}

{{center|
{{Annotated image
 |image=Hydra, Nix, Styx conjunctions cycle.png
 |image-width=625
 |width=625
 |height=124<!-- to crop the lower part of the image -->
 |float=center
 |annotations=<!-- this parameter must be there, empty or not! -->
 |caption=Sequence of conjunctions of Hydra (blue), Nix (red) and Styx (black) over one third of their resonance cycle. Movements are counterclockwise and orbits completed are tallied at upper right of diagrams (click on image to see the whole cycle).}}
}}

== Exploration ==
{{multiple image
 |direction=horizontal
 |align=right
 |width1=121
 |width2=130
 |image1=Nix in Color Released September 11 2015.png
 |image2=Pluto's Moon Nix, Half Illuminated.jpg
 |caption1=LORRI and MVIC color composite image of Nix
 |caption2=Nix half illuminated, imaged by ''[[New Horizons]]''}}

The ''[[New Horizons]]'' spacecraft visited the Pluto system and photographed Pluto and its moons during its flyby on 14 July 2015. Of Pluto's smaller moons, only Nix and Hydra were imaged at resolutions high enough for surface features to be visible.<ref name="DPS15" /> Prior to the flyby of the Pluto system, measurements of Nix's size were performed by the [[Long Range Reconnaissance Imager]] on board ''New Horizons'', initially estimating Nix to be about {{convert|35|km|mi|abbr=on}} in diameter.<ref name="Measurement">{{cite web |url= http://www.nasa.gov/feature/how-big-is-pluto-new-horizons-settles-decades-long-debate/ |title=How Big Is Pluto? ''New Horizons'' Settles Decades-Long Debate|date=13 July 2015 |publisher=[[NASA]] |access-date=13 July 2015}}</ref> The first detailed images of Nix taken by ''New Horizons'' from a distance of about {{convert|231000|km|mi|abbr=on}} were downlinked, or received from the spacecraft on 18 July 2015 and released to the public on 21 July 2015.<ref name="nasa.gov" /> With an image resolution {{convert|3|km|mi|abbr=on}} per pixel, Nix's shape was often referred to as a "jelly bean" shape.<ref name="nasa.gov" /> Enhanced color images from the [[Ralph (New Horizons)|Ralph MVIC]] instrument of ''New Horizons'' show a reddish region on its surface.<ref name="nasa.gov" /> From those images, another accurate measurement of Nix's dimensions was made, giving the approximate dimensions of {{convert|42|×|36|km|mi|abbr=on}}.<ref name="nasa.gov" />
{{clear}}

== Notes ==
{{notelist}}

== References ==

{{reflist
| colwidth = 30em
| refs =

<ref name="scimag000">{{cite journal|last1=Stern|first1=S. A.|last2=Bagenal|first2=F.|last3=Ennico|first3=K.|last4=Gladstone|first4=G. R.|title=The Pluto system: Initial results from its exploration by New Horizons|journal=Science|date=15 October 2015|volume=350|issue=6258|pages=aad1815|doi=10.1126/science.aad1815|pmid=26472913|display-authors=etal|arxiv = 1510.07704 |bibcode = 2015Sci...350.1815S |s2cid=1220226}}</ref>

<ref name="Buie_2006">{{cite journal| doi = 10.1086/504422| last1 = Buie| first1 = Marc W.| last2 = Grundy| first2 = William M.| last3 = Young| first3 = Eliot F.| last4 = Young| first4 = Leslie A.| last5 = Stern| first5 = S. Alan| year = 2006| title = Orbits and Photometry of Pluto's Satellites: Charon, S/2005 P1, and S/2005 P2| journal = The Astronomical Journal| volume = 132| issue = 1| pages = 290–298| bibcode = 2006AJ....132..290B| arxiv = astro-ph/0512491| s2cid = 119386667}}. ''a, i, e'' per [http://ssd.jpl.nasa.gov/?sat_elem#pluto JPL] (site updated 2008 Aug 25)</ref>

<ref name="arxiv0511837">{{cite journal|journal=The Astronomical Journal |author=Steffl, A. J. |display-authors=4 |author2=Mutchler, M. J. |author3=Weaver, H. A. |author4=Stern, S. A. |author5=Durda, D. D. |author5-link=Daniel David Durda |author6=Terrell, D. |author6-link=Dirk Terrell |author7=Merline, W. J. |author8=Young, L. A. |author9=Young, E. F. |author10=Buie, M. W. |author11=Spencer, J. R. |name-list-style=amp |date=2006 |title=New Constraints on Additional Satellites of the Pluto System |volume=132|issue=2 |pages=614–619 |doi=10.1086/505424 |bibcode=2006AJ....132..614S|arxiv = astro-ph/0511837 |s2cid=10547358 }}([https://arxiv.org/abs/astro-ph/0511837 Final preprint])</ref>

<ref name="nomenclature">{{cite web|title=Naming of Astronomical Objects|url=https://www.iau.org/public/themes/naming/#dwarfplanets|publisher=International Astronomical Union}}</ref>

<ref name="phasecurves">{{cite journal |last1=Verbiscer |first1=A. J. |last2=Porter |first2=S. B. |last3=Buratti |first3=B. J. |last4=Weaver |first4=H. A. |last5=Spencer |first5=J. R. |last6=Showalter |first6=M. R. |last7=Buie |first7=M. W. |last8=Hofgartner |first8=J. D. |last9=Hicks |first9=M. D. |last10=Ennico-Smith |first10=K. |last11=Olkin |first11=C. B. |last12=Stern |first12=S. A. |last13=Young |first13=L. A. |last14=Cheng |first14=A. |title=Phase Curves of Nix and Hydra from the ''New Horizons'' Imaging Cameras |journal=The Astrophysical Journal |date=2018 |volume=852 |issue=2 |pages=L35 |doi=10.3847/2041-8213/aaa486|doi-access=free |bibcode=2018ApJ...852L..35V }}</ref>

<ref name="tidaldamping">{{cite arXiv|eprint=0802.2939|last1=Stern|first1=S. A.|title=The Effect of Charon's Tidal Damping on the Orbits of Pluto's Three Moons|last2=Mutchler|first2=M. J.|last3=Weaver|first3=H. A.|last4=Steffl|first4=A. J.|class=astro-ph|year=2008}}</ref>

<ref name="arxiv0802.2951">{{cite arXiv |eprint=0802.2951|last1=Stern|first1=S. A.|title=On the Origin of Pluto's Minor Moons, Nix and Hydra|last2=Mutchler|first2=M. J.|last3=Weaver|first3=H. A.|last4=Steffl|first4=A. J.|class=astro-ph|year=2008}}</ref>

<ref name="Weaver2016">{{cite journal
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  |first1 = H. A. |last1 = Weaver
  |first2 = M. W. |last2 = Buie
  |first3 = B. J. |last3 = Buratti
  |first4 = W. M. |last4 = Grundy
  |first5 = T. R. |last5 = Lauer 
  |first6 = C. B. |last6 = Olkin
  |title      = The Small Satellites of Pluto as Observed by New Horizons
  |journal    = Science
  |date       = March 2016
  |volume     = 351
  |issue      = 6279
  |id         = aae0030
  |pages      = 5
  |doi        = 10.1126/science.aae0030
  |arxiv      = 1604.05366
  |bibcode    = 2016Sci...351.0030W
  |pmid       = 26989256
  |s2cid      = 206646188}}</ref>

<ref name="Weaver2016-supp">{{cite journal
  |display-authors = etal
  |first1 = H. A. |last1 = Weaver
  |first2 = M. W. |last2 = Buie
  |first3 = B. J. |last3 = Buratti
  |first4 = W. M. |last4 = Grundy
  |first5 = T. R. |last5 = Lauer 
  |first6 = C. B. |last6 = Olkin
  |title      = Supplementary Materials for The Small Satellites of Pluto as Observed by New Horizons
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  |journal    = Science
  |date       = March 2016
  |volume     = 351
  |issue      = 6279
  |id         = aae0030
  |pages      = 25
  |doi        = 10.1126/science.aae0030
  |arxiv      = 1604.05366
  |bibcode    = 2016Sci...351.0030W
  |pmid       = 26989256
  |s2cid      = 206646188}}</ref>

<ref name="Porter2023">{{cite journal
  |first1 = Simon B. |last1 = Porter
  |first2 = Robin M. |last2 = Canup
  |title      = Orbits and Masses of the Small Satellites of Pluto
  |journal    = The Planetary Science Journal
  |date       = July 2023
  |volume     = 4
  |issue      = 7
  |id         = 120
  |pages      = 14
  |doi-access = free
  |doi        = 10.3847/PSJ/acde77
  |arxiv      = 2307.04848
  |bibcode    = 2023PSJ.....4..120P
  |s2cid      = }}</ref>
}}

== External links ==
{{Commons category|Nix}}
* [https://web.archive.org/web/20060626220516/http://www.boulder.swri.edu/plutonews/ Background Information Regarding Our Two Newly Discovered Satellites of Pluto] – The discoverers' website
* [http://hubblesite.org/newscenter/newsdesk/archive/releases/2005/19/ NASA's Hubble Reveals Possible New Moons Around Pluto] – Hubble press release
* [https://solarsystem.nasa.gov/moons/pluto-moons/nix/in-depth/ Nix In Depth] – NASA Solar System Exploration

{{Pluto}}
{{Moons of dwarf planets}}
{{Trans-Neptunian objects}}
{{Portal bar|Astronomy|Stars|Spaceflight|Outer space|Solar System}}
[[Category:Moons of Pluto]]
[[Category:Astronomical objects discovered in 2005|20050615]]
[[Category:Nyx]]
[[Category:Moons with a prograde orbit]]