Moons of Pluto

The innermost and largest moon, Charon, was discovered by James Christy on 22 June 1978, nearly half a century after Pluto was discovered. This led to a substantial revision in estimates of Pluto's size, which had previously assumed that the observed mass and reflected light of the system were all attributable to Pluto alone.

Two additional moons were imaged by astronomers of the Pluto Companion Search Team preparing for the New Horizons mission and working with the Hubble Space Telescope on 15 May 2005, which received the provisional designations S/2005 P 1 and S/2005 P 2. The International Astronomical Union officially named these moons Nix (Pluto II, the inner of the two moons, formerly P 2) and Hydra (Pluto III, the outer moon, formerly P 1), on 21 June 2006.

{{cite journal

| first=Daniel W. E. |last=Green

| title = Satellites of Pluto

| journal = IAU Circular

| issue = 8723

| date = 21 June 2006

| url = http://www.cbat.eps.harvard.edu/iauc/08700/08723.html#Item1

| access-date = 26 November 2011

}}

{{cite web

| url = http://www.nasa.gov/mission_pages/hubble/science/pluto-moon.html

| title = NASA's Hubble Discovers Another Moon Around Pluto

| publisher = NASA

| date = 20 July 2011

| access-date = 20 July 2011

}}

Kerberos, announced on 20 July 2011, was discovered while searching for Plutonian rings. The discovery of Styx was announced on 7 July 2012 while looking for potential hazards for New Horizons.{{Cite web |title = Hubble Discovers a Fifth Moon Orbiting Pluto |url = http://hubblesite.org/newscenter/archive/releases/2012/32/full/ |website = hubblesite.org |access-date = 2015-07-29 |date = 29 July 2012 |archive-url=https://web.archive.org/web/20121117053628/http://hubblesite.org/newscenter/archive/releases/2012/32/full/ |archive-date=17 November 2012 |url-status=dead}}

File:Nh-pluto moons family portrait.png

File:PIA19856-PlutoCharon-NewHorizons-Color-20150714.jpg

{{Main|Charon (moon)}}

Charon is about half the diameter of Pluto and is massive enough (nearly one eighth of the mass of Pluto) that the system's barycenter lies between them, approximately {{convert|960|km}} above Pluto's surface.{{cite web |author=Staff |title=Barycenter |url=http://www.education.com/science-fair/article/barycenter-balancing-point/ |date=30 January 2014 |work=Education.com |access-date=4 June 2015 }}{{cite web|url=http://wwwsa.boulder.swri.edu/P1P2_motion.avi |title=P1P2_motion.avi |format=AVI |url-status=dead |archive-url=https://web.archive.org/web/20051104094343/http://wwwsa.boulder.swri.edu/P1P2_motion.avi |archive-date=4 November 2005 }} and barycenter for animations Charon and Pluto are also tidally locked, so that they always present the same face toward each other. The IAU General Assembly in August 2006 considered a proposal that Pluto and Charon be reclassified as a double planet, but the proposal was abandoned.{{cite web|title=The IAU draft definition of "planet" and "plutons"|url=http://www.iau.org/public_press/news/release/iau0601/|publisher=International Astronomical Union|date=16 August 2006|access-date=4 June 2015 }}

Like Pluto, Charon is a perfect sphere to within measurement uncertainty.

{{cite journal |last1=Nimmo |first1=Francis |display-authors=etal |title=Mean radius and shape of Pluto and Charon from New Horizons images|journal=Icarus |date=2017 |volume=287 |pages=12–29 |doi=10.1016/j.icarus.2016.06.027|bibcode=2017Icar..287...12N |arxiv=1603.00821|s2cid=44935431 }}

{{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}}{{·}}{{legend2|Lime| Styx}}{{·}}{{legend2|Magenta| Nix}}{{·}}{{legend2|Cyan| Kerberos}}{{·}}{{legend2|Orangered| Hydra}}

}}

{{multiple image |align=right |direction=horizontal

|image1 = Pluto system 2006.jpg

|caption1 =The Hubble discovery image of Nix and Hydra

|image2 = Pluto moon P5 discovery with moons' orbits.jpg

|caption2 = Discovery image of Styx, overlaid with orbits of the satellite system}}

Pluto's four small circumbinary moons orbit Pluto at two to four times the distance of Charon, ranging from Styx at 42,700 kilometres to Hydra at 64,800 kilometres from the barycenter of the system. They have nearly circular prograde orbits in the same orbital plane as Charon.

All are much smaller than Charon. Nix and Hydra, the two larger, are roughly 42 and 55 kilometers on their longest axis respectively,{{Cite web|title = New Horizons 'Captures' Two of Pluto's Smaller Moons|url = http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150721|website = New Horizons|access-date = 2015-07-29}} and Styx and Kerberos are 7 and 12 kilometers respectively.{{Cite news |last=Gipson |first=Lillian |date=2015-10-09 |title=New Horizons Picks Up Styx |url=http://www.nasa.gov/nh/new-horizons-picks-up-styx/ |archive-url=https://web.archive.org/web/20151010222508/http://www.nasa.gov/nh/new-horizons-picks-up-styx/ |archive-date=2015-10-10 |access-date=2025-06-23 |work=NASA |language=en}}{{Cite news |last=Talbert |first=Tricia |date=2015-10-22 |title=Last of Pluto’s Moons – Mysterious Kerberos – Revealed by New Horizons |url=https://www.nasa.gov/feature/last-of-pluto-s-moons-mysterious-kerberos-revealed-by-new-horizons/ |archive-url=http://web.archive.org/web/20230410143041/https://www.nasa.gov/feature/last-of-pluto-s-moons-mysterious-kerberos-revealed-by-new-horizons/ |archive-date=2023-04-10 |access-date=2025-06-23 |work=NASA |language=en}} All four are irregularly shaped.

The Pluto system is highly compact and largely empty: prograde moons could stably orbit Pluto out to 53% of the Hill radius (the gravitational zone of Pluto's influence) of 6 million km, or out to 69% for retrograde moons. However, only the inner 3% of the region where prograde orbits would be stable is occupied by satellites,{{cite arXiv | first1=S. Alan |last1=Stern| first2=Harold A. Jr. |last2=Weaver| first3=Andrew J. |last3=Steffl | display-authors=3| first4=Max J. |last4=Mutchler| first5=William J. |last5=Merline| first6=Marc W. |last6=Buie| first7=Eliot F. |last7=Young| first8=Leslie A. |last8=Young| first9=John R. |last9=Spencer| title = Characteristics and Origin of the Quadruple System at Pluto | date = 2005| eprint = astro-ph/0512599}} and the region from Styx to Hydra is packed so tightly that there is little room for further moons with stable orbits within this region.{{cite journal|last1=Kenyon|first1=S. J.|title=Astronomy: Pluto leads the way in planet formation|journal= Nature|volume= 522|issue= 7554|date= 2015-06-03|pages= 40–41|doi= 10.1038/522040a|bibcode = 2015Natur.522...40K|pmid=26040888|s2cid=205085254|doi-access= free}}

An intense search conducted by New Horizons confirmed that no moons larger than 4.5 km in diameter exist out to distances up to 180,000 km from Pluto (6% of the stable region for prograde moons), assuming Charon-like albedoes of 0.38 (for smaller distances, this threshold is still smaller).

{{multiple image |image1=Masses of Plutonian moons.png |caption1=The relative masses of Pluto's moons. Charon dominates the system. Nix and Hydra are barely visible and Styx and Kerberos are invisible at this scale.

|image2=Pluto-Charon system-new.gif

|caption2=An oblique schematic view of the Pluto–Charon system showing that Pluto orbits a point outside itself. Also visible is the mutual tidal locking between the two bodies.}}

The orbits of the moons are confirmed to be circular and coplanar, with inclinations differing less than 0.4° and eccentricities less than 0.005.{{cite web |url=http://hubblesite.org/newscenter/newsdesk/archive/releases/2005/19/image/h |title=Orbits of 4 Bodies in Pluto System about Barycenter as Seen from Earth |publisher=Hubblesite |access-date=21 June 2006}}

The discovery of Nix and Hydra suggested that Pluto could have a ring system. Small-body impacts could eject debris off of the small moons which can form into a ring system. However, data from a deep-optical survey by the Advanced Camera for Surveys on the Hubble Space Telescope, by occultation studies,

{{cite journal

| first1=Jay M. |last1=Pasachoff

| first2=Bryce A. |last2=Babcock

| first3=Steven P. |last3=Souza

| display-authors=3

| first4=Joseph W. |last4=Gangestad

| first5=Anne E. |last5=Jaskot

| first6=James L. |last6=Elliot

| first7=Amanda A. S. |last7=Gulbis

| first8=Michael J. |last8=Person

| first9=E. A. |last9=Kramer

| first10=Elisabeth R. |last10=Adams

| first11=Carlos A. |last11=Zuluaga

| first12=Rosemary E. |last12=Pike

| first13=Paul J. |last13=Francis

| first14=R. |last14=Lucas

| first15=Amanda S. |last15=Bosh

| first16=David J. |last16=Ramm

| first17=John G. |last17=Greenhill

| first18=A. Barry |last18=Giles

| first19=Stefan W. |last19=Dieters

| date = 2006

| title = A Search for Rings, Moons, or Debris in the Pluto System during the 2006 July 12 Occultation

| journal = Bulletin of the American Astronomical Society

| volume = 38

| issue = 3

| page = 523

| bibcode = 2006DPS....38.2502P

}}

and later by New Horizons, suggest that no ring system is present.

Styx, Nix, and Hydra are thought to be in a 3-body Laplace orbital resonance with orbital periods in a ratio of 18:22:33.{{cite book| title=Pluto & Charon| author=Codex Regius| url=https://books.google.com/books?id=dTs2DQAAQBAJ&pg=PT197| page=197| year=2016| publisher=XinXii| isbn= 9781534633520| access-date=13 March 2018}} The ratios should be exact when orbital precession is taken into account. Nix and Hydra are in a simple 2:3 resonance.The ratio of 18:22:33 in the 3-body resonance corresponds to a 2-body resonance with ratio 2:3 between Hydra and Nix.{{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}}{{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}} Styx and Nix are in an 9:11 resonance, while the resonance between Styx and Hydra has a ratio of 6:11.The ratio of 18:22:33 in the 3-body resonance corresponds to a 2-body resonance with ratio 9:11 between Styx and Nix. In analogy, the ratio of 18:22:33 in the 3-body resonance corresponds to a 2-body resonance with ratio 6:11 between Styx and Hydra. The Laplace resonance also means that ratios of synodic periods are then such that there are 5 Styx–Hydra conjunctions and 3 Nix–Hydra conjunctions for every 2 conjunctions of Styx and Nix.This is calculated as follows: for every $1$ orbit of Hydra there are $\backslash frac\{33\}\{22\}=\backslash frac\; 32$ orbits of Nix and $\backslash frac\{33\}\{18\}=\backslash frac\{11\}\{6\}$ orbits of Styx. The conjunctions then occur at a relative rate of $\backslash frac\{11\}\{6\}-1=\backslash frac\{5\}\{6\}$ for Styx-Hydra, $\backslash frac\{3\}\{2\}-1=\backslash frac\; 12$ for Nix-Hydra and $\backslash frac\{11\}\{6\}-\backslash frac\{3\}\{2\}=\backslash frac\; 13$ for Styx-Nix. Multiplying all three rates by $6$ (to make them integers) yields that there are $5$ Styx-Hydra conjunctions and $3$ Nix-Hydra conjunctions for every $2$ Styx-Nix conjunctions. If $\backslash lambda$ denotes the mean longitude and $\backslash Phi$ the libration angle, then the resonance can be formulated as $\backslash Phi=3\backslash lambda\_\{\backslash rm\; Styx\}\; -\; 5\backslash lambda\_\{\backslash rm\; Nix\}\; +\; 2\backslash lambda\_\{\backslash rm\; Hydra\}=180^\backslash circ$. As with the Laplace resonance of the Galilean satellites of Jupiter, triple conjunctions never occur. $\backslash Phi$ librates about 180° with an amplitude of at least 10°.

All of the outer circumbinary moons are also close to mean motion resonance with the Charon–Pluto orbital period. Styx, Nix, Kerberos, and Hydra are in a 1:3:4:5:6 sequence of near resonances, with Styx approximately 5.4% from its resonance, Nix approximately 2.7%, Kerberos approximately 0.6%, and Hydra approximately 0.3%.{{cite web

| last = Matson | first = J. | date = 11 July 2012 | title = New Moon for Pluto: Hubble Telescope Spots a 5th Plutonian Satellite

| work = Scientific American web site | url = http://www.scientificamerican.com/article.cfm?id=pluto-moon-p5

| access-date = 12 July 2012}} It may be that these orbits originated as forced resonances when Charon was tidally boosted into its current synchronous orbit, and then released from resonance as Charon's orbital eccentricity was tidally damped. The Pluto–Charon pair creates strong tidal forces, with the gravitational field at the outer moons varying by 15% peak to peak.{{Citation needed|date=June 2015}}

However, it was calculated that a resonance with Charon could boost either Nix or Hydra into its current orbit, but not both: boosting Hydra would have required a near-zero Charonian eccentricity of 0.024, whereas boosting Nix would have required a larger eccentricity of at least 0.05. This suggests that Nix and Hydra were instead captured material, formed around Pluto–Charon, and migrated inward until they were trapped in resonance with Charon.{{cite arXiv|eprint=0802.2951|class=astro-ph|last=Lithwick|first=Y.|author2=Y. Wu|title=On the Origin of Pluto's Minor Moons, Nix and Hydra|year=2008}} The existence of Kerberos and Styx may support this idea.{{clarification needed|date=March 2024}}{{Citation needed|date=April 2024}}

{{Annotated image

|image = Hydra, Nix, Styx orbital resonance cycle.png

|image-width = 450

|width=450

| height = 112

| float = center

| annotations =

| caption = {{center|Configurations of Hydra (blue), Nix (red) and Styx (black) over one quarter of the cycle of their mutual orbital resonance. Movements are counterclockwise and orbits completed are tallied at upper right of diagrams (click on image to see the complete cycle).}}}}

{{Clear}}

File:PIA20052-SmallMoonsOfPluto-Animation-20151110.webm

Prior to the New Horizons mission,

Nix, Hydra, Styx, and Kerberos

were predicted to rotate chaotically or tumble.{{cite journal

| last1 = Correia | first1 = A. C. M.| last2 = Leleu | first2 = A. | last3 = Rambaux | first3 = N.| last4 = Robutel | first4 = P.| title = Spin-orbit coupling and chaotic rotation for circumbinary bodies. Application to the small satellites of the Pluto-Charon system | journal=Astronomy and Astrophysics | volume = 580 | pages = L7| doi = 10.1051/0004-6361/201526800 |bibcode = 2015A&A...580L..14C| year = 2015| arxiv = 1506.06733| s2cid = 119098216}}

However, New Horizons imaging found that they had not tidally

spun down to near a spin synchronous state where chaotic rotation or tumbling would be expected.{{ cite journal | last1 = Weaver | first1 = H. A. | title = The Small Satellites of Pluto as Observed by New Horizons | journal=Science | volume = 351 | issue = 6279 | pages = 1281 | doi= 10.1126/science.aae0030| year = 2016 | bibcode = 2016Sci...351.0030W | arxiv = 1604.05366 | pmid = 26989256 | s2cid = 206646188 }}{{ cite journal | last1 = Quillen |first1 = A. C. | last2 = Nichols-Fleming | first2 = F. | last3= Chen | first3=Y.-Y.| last4 = Noyelles| first4 = B.| title=Obliquity evolution of the minor satellites of Pluto and Charon | journal=Icarus | volume=293 | pages= 94–113 |doi = 10.1016/j.icarus.2017.04.012 |bibcode = 2017Icar..293...94Q |year = 2017 |arxiv = 1701.05594 |s2cid = 119408999 }} New Horizons imaging found that all 4 moons were at high obliquity. Either they were born that way, or they were tipped by a spin precession resonance.

Styx may be experiencing intermittent and chaotic obliquity variations.

Mark R. Showalter had speculated that, "Nix can flip its entire pole. It could actually be possible to spend a day on Nix in which the sun rises in the east and sets in the north. It is almost random-looking in the way it rotates."{{cite news |last=Chang |first=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 |date=3 June 2015 |work=New York Times |access-date=4 June 2015 }}

Only one other moon, Saturn's moon Hyperion, is known to tumble,{{cite journal| last1 = Wisdom | first1 = J.| last2 = Peale | first2 = S. J. | last3 = Mignard | first3 = F. | title = The chaotic rotation of Hyperion | journal= Icarus | volume = 58 | issue = 2| pages = 137–152| doi = 10.1016/0019-1035(84)90032-0 |bibcode = 1984Icar...58..137W| year = 1984| citeseerx = 10.1.1.394.2728}} though it is likely that Haumea's moons do so as well.{{Cite web|title = Rapidly Rotating Regular Satellites and Tides |url = http://www.planetary.org/blogs/guest-blogs/2016/1017-rapidly-rotating-regular-satellites-and-tides.html |website = Planetary Society |date=17 October 2016|access-date = 12 September 2017 |first = Darin|last = Ragozzine}}{{failed verification|date=May 2025}}

File:Creation of the moons of Pluto.jpg approaches Pluto; 2: it collides with Pluto; 3: a dust ring forms around Pluto; 4: the debris aggregates to form Charon; 5: Pluto and Charon relax into spherical bodies.]]

It is suspected that Pluto's satellite system was created by a massive collision, similar to the Theia impact thought to have created the Moon.{{cite journal

| last = Canup | first = R. M. | author-link = Robin Canup | title = A Giant Impact Origin of Pluto-Charon

| journal = Science | volume = 307 | issue = 5709 | pages = 546–550

| date = 8 January 2005

| doi = 10.1126/science.1106818 |bibcode = 2005Sci...307..546C | pmid=15681378| s2cid = 19558835 | url = https://authors.library.caltech.edu/51983/7/Canup.SOM.pdf }}{{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 |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=2011-07-20 |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 }} In both cases, the high angular momenta of the moons can only be explained by such a scenario. The nearly circular orbits of the smaller moons suggests that they were also formed in this collision, rather than being captured Kuiper Belt objects. This and their near orbital resonances with Charon (see below) suggest that they formed closer to Pluto than they are at present and migrated outward as Charon reached its current orbit. Their grey color is different from that of Pluto, one of the reddest bodies in the Solar System. This is thought to be due to a loss of volatiles during the impact or subsequent coalescence, leaving the surfaces of the moons dominated by water ice. However, such an impact should have created additional debris (more moons), yet no moons or rings were discovered by New Horizons, ruling out any more moons of significant size orbiting Pluto. An alternative hypothesis is that the collision happened at about 2,000 miles per hour, not powerful enough to destroy Charon and Pluto. Instead they remained attached to each other for up to ten hours before separating again. The faster rotation of Pluto back then, with one rotation every third hour, would have created a centrifugal force stronger than the gravitational attraction between the two bodies, which made Charon separate from Pluto, but remained gravitationally bound with each other. The same process could have created the four other known moons, from material that escaped Pluto and Charon.{{Cite news |last=O’Callaghan |first=Jonathan |date=2025-01-08 |title=Pluto May Have Captured Its Biggest Moon After an Ancient Dance and Kiss |url=https://www.nytimes.com/2025/01/08/science/pluto-moon-kiss-charon.html |access-date=2025-06-23 |work=The New York Times |language=en-US |issn=0362-4331}}

Pluto's moons are listed here by orbital period, from shortest to longest. Charon, which is massive enough to have collapsed into a spheroid under its own gravitation, is highlighted in light purple. As the system barycenter lies far above Pluto's surface, Pluto's barycentric orbital elements have been included as well.Orbital elements of small satellites from Showalter and Hamilton, 2015; mass and magnitude from{{Cite web |last=Steffl |first=A. J. |last2=Mutchler |first2=M. J. |last3=Weaver |first3=H. A. |last4=Stern |first4=S. A. |last5=Durda |first5=D. D. |last6=Terrell |first6=D. |last7=Merline |first7=W. J. |last8=Young |first8=L. A. |last9=Young |first9=E. F. |date=2005-11-30 |title=New Constraints on Additional Satellites of the Pluto System |url=https://arxiv.org/abs/astro-ph/0511837v3 |access-date=2025-06-23 |website=arXiv.org |language=en}} All elements are with respect to the Pluto-Charon barycenter. The mean separation distance between the centers of Pluto and Charon is 19,596 km.

{{sticky table start}}

{{sticky table end}}

File:Pluto and Charon system new.png|Pluto and its five moons, including the location of the system's barycenter. Sizes and distances of the bodies are to scale.

{{Clear}}

{{more citations needed|section|date = July 2021}}

File:Charon Eclipses Pluto on 25 February 1989.jpg

Transits occur when one of Pluto's moons passes between Pluto and the Sun. This occurs when one of the satellites' orbital nodes (the points where their orbits cross Pluto's ecliptic) lines up with Pluto and the Sun. This can only occur at two points in Pluto's orbit; coincidentally, these points are near Pluto's perihelion and aphelion. Occultations occur when Pluto passes in front of and blocks one of Pluto's satellites.

Charon has an angular diameter of 4 degrees of arc as seen from the surface of Pluto; the Sun appears much smaller, only 39 to 65 arcseconds. By comparison, the Moon as viewed from Earth has an angular diameter of only 31 minutes of arc, or just over half a degree of arc. Therefore, Charon would appear to have eight times the diameter, or 64 times the area of the Moon; this is due to Charon's proximity to Pluto rather than size, as despite having just over one-third of a Lunar radius, Earth's Moon is 20 times more distant from Earth's surface as Charon is from Pluto's. This proximity further ensures that a large proportion of Pluto's surface can experience an eclipse. Because Pluto always presents the same face towards Charon due to tidal locking, only the Charon-facing hemisphere experiences solar eclipses by Charon.

The smaller moons can cast shadows elsewhere. The angular diameters of the four smaller moons (as seen from Pluto) are uncertain. Nix's is 3–9 minutes of arc and Hydra's is 2–7 minutes. These are much larger than the Sun's angular diameter, so total solar eclipses are caused by these moons.

Eclipses by Styx and Kerberos are more difficult to estimate, as both moons are very irregular, with angular dimensions of 76.9 x 38.5 to 77.8 x 38.9 arcseconds for Styx, and 67.6 x 32.0 to 68.0 x 32.2 for Kerberos. As such, Styx has no annular eclipses, its widest axis being more than 10 arcseconds larger than the Sun at its largest. However, Kerberos, although slightly larger, cannot make total eclipses as its largest minor axis is a mere 32 arcseconds. Eclipses by Kerberos and Styx will entirely consist of partial and hybrid eclipses, with total eclipses being extremely rare.

The next period of mutual events due to Charon will begin in October 2103, peak in 2110, and end in January 2117. During this period, solar eclipses will occur once each Plutonian day, with a maximum duration of 90 minutes.{{cite web

|date = 12 December 1987

|title = Start of Eclipse

|publisher = JPL Solar System Simulator

|url = http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=901&vbody=999&month=12&day=12&year=1987&hour=11&minute=28&fovmul=1&rfov=5&bfov=30&porbs=1&brite=1

|archive-url = https://web.archive.org/web/20170324031702/http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=901&vbody=999&month=12&day=12&year=1987&hour=11&minute=28&fovmul=1&rfov=5&bfov=30&porbs=1&brite=1

|url-status = dead

|archive-date = 24 March 2017

|access-date = 2014-07-29}} [https://web.archive.org/web/20170324034439/http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=999&vbody=10&month=12&day=12&year=1987&hour=12&minute=12&rfov=20&fovmul=-1&bfov=50&porbs=1&brite=1 (Pluto as seen from the Sun during mid-eclipse)]{{cite web

|date = 12 December 1987

|title = End of Eclipse

|publisher = JPL Solar System Simulator

|url = http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=901&vbody=999&month=12&day=12&year=1987&hour=12&minute=57&fovmul=1&rfov=5&bfov=30&porbs=1&brite=1

|archive-url = https://web.archive.org/web/20170324062349/http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=901&vbody=999&month=12&day=12&year=1987&hour=12&minute=57&fovmul=1&rfov=5&bfov=30&porbs=1&brite=1

|url-status = dead

|archive-date = 24 March 2017

|access-date = 2014-07-29}}

The Pluto system was visited by the New Horizons spacecraft in July 2015. Images with resolutions of up to 330 meters per pixel were returned of Nix and up to 1.1 kilometers per pixel of Hydra. Lower-resolution images were returned of Styx and Kerberos.{{Cite web |url=http://pluto.jhuapl.edu/Mission/The-Flyby.php |title=New Horizons flyby timeline |access-date=25 July 2015 |archive-url=https://web.archive.org/web/20150715172512/http://pluto.jhuapl.edu/Mission/The-Flyby.php |archive-date=15 July 2015 |url-status=dead }}

{{Notelist}}

{{Reflist|2|refs=

{{cite journal

|title =New Constraints on Additional Satellites of the Pluto System

|author1=Steffl, A. J. |author2=Mutchler, M. J. |author3=Weaver, H. A. |author4=Stern, S. A. |author5=Durda, D. D. |author6=Terrell, D. |author7=Merline, W. J. |author8=Young, L. A. |author9=Young, E. F. |author10=Buie, M. W. |author11=Spencer, J. R. |date =2006

|journal=The Astronomical Journal

|volume =132

|issue =2

|pages =614–619

|doi =10.1086/505424

|bibcode=2006AJ....132..614S

|arxiv =astro-ph/0511837

|s2cid=10547358 }}

{{cite journal

|title =The Pluto system: Initial results from its exploration by New Horizons

|author1=Stern, S. A. |author2=Bagenal, F. |author3=Ennico, K. |date =2015

|journal=Science

|volume =350

|issue =6258

|doi =10.1126/science.aad1815

|bibcode=2015Sci...350.1815S

|pmid =26472913

|arxiv =1510.07704

|display-authors=etal

|pages=aad1815|s2cid=1220226 }} ([http://www.sciencemag.org/content/suppl/2015/10/14/350.6258.aad1815.DC1/Stern.SM.pdf Supplements])

}}

• {{cite arXiv |eprint=astro-ph/0512599|last1=Stern|first1=S. A.|last2=Weaver|first2=H. A.|last3=Steffl|first3=A. J.|last4=Mutchler|first4=M. J.|last5=Merline|first5=W. J.|last6=Buie|first6=M. W.|last7=Young|first7=E. F.|last8=Young|first8=L. A.|last9=Spencer|first9=J. R.|title=Characteristics and Origin of the Quadruple System at Pluto|year=2005}}
• {{cite journal

|title =New Constraints on Additional Satellites of the Pluto System

|author1=Steffl, A. J. |author2=Mutchler, M. J. |author3=Weaver, H. A. |author4=Stern, S. A. |author5=Durda, D. D. |author6=Terrell, D. |author7=Merline, W. J. |author8=Young, L. A. |author9=Young, E. F. |author10=Buie, M. W. |author11=Spencer, J. R. |date =2006

|journal=The Astronomical Journal

|volume =132

|issue =2

|pages =614–619

|doi =10.1086/505424

|bibcode=2006AJ....132..614S

|arxiv =astro-ph/0511837

|s2cid=10547358 }}

• {{cite journal |arxiv=astro-ph/0512491|doi=10.1086/504422|bibcode=2006AJ....132..290B|title=Orbits and Photometry of Pluto's Satellites: Charon, S/2005 P1, and S/2005 P2|year=2006|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|journal=The Astronomical Journal|volume=132|issue=1|pages=290–298|s2cid=119386667}}
• {{cite journal |doi=10.1016/j.icarus.2014.03.015|bibcode=2015Icar..246..317B|title=The orbits and masses of satellites of Pluto|year=2015|last1=Brozović|first1=Marina|last2=Showalter|first2=Mark R.|last3=Jacobson|first3=Robert A.|last4=Buie|first4=Marc W.|journal=Icarus|volume=246|pages=317–329}}
• Codex Regius (2016), Pluto & Charon, CreateSpace Independent Publishing Platform {{ISBN|978-1534960749}}
• [http://www.cbat.eps.harvard.edu/iauc/08600/08625.html IAU Circular No. 8625], describing the discovery of 2005 P1 and P2
• [http://www.cbat.eps.harvard.edu/iauc/08600/08686.html IAU Circular No. 8686], reporting a more neutral color for 2005 P2
• [http://www.cbat.eps.harvard.edu/iauc/08700/08723.html IAU Circular No. 8723] announcing the names of Nix and Hydra
• [https://web.archive.org/web/20060626220516/http://www.boulder.swri.edu/plutonews/ Background Information Regarding Our Two Newly Discovered Satellites of Pluto] – The website of the discoverers of Nix and Hydra

{{Commons category}}

• Scott S. Sheppard: [https://sites.google.com/carnegiescience.edu/sheppard/moons/plutomoons Pluto Moons]
• [https://thehappykoala.github.io/Harmony-of-the-Spheres/#/scenario/The%20Sun%20and%20the%20Plutonian%20System Interactive 3D visualisation of the Plutonian system]
• [https://web.archive.org/web/20051104094343/http://wwwsa.boulder.swri.edu/P1P2_motion.avi Animation of the Plutonian system]
• [http://www.nasa.gov/vision/universe/solarsystem/hubble_pluto.html Hubble Spots Possible New Moons Around Pluto] (NASA)
• [http://www.space.com/scienceastronomy/051031_pluto_moons.html Two More Moons Discovered Orbiting Pluto] (SPACE.com)
• [http://www.pluto.jhuapl.edu New Horizons Mission Site]

{{Pluto}}

{{Charon (moon)}}

{{Moons of dwarf planets}}

{{Solar System moons (compact)}}

{{Solar System}}

{{Portal bar|Astronomy|Stars|Spaceflight|Outer space|Solar system}}

{{Authority control}}

{{DEFAULTSORT:Moons Of Pluto}}

Category:Lists of moons

Category:Articles containing video clips

Category:Solar System