A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are often colloquially referred to as ''moons'', a derivation from the Moon of Earth. In the Solar System, there are six planetary satellite systems containing 209 known natural satellites altogether. Seven objects commonly considered dwarf planets by astronomers are also known to have natural satellites: , Pluto, Haumea, , Makemake, , and Eris. , there are 442 other minor planets known to have natural satellites. A planet usually has at least around 10,000 times the mass of any natural satellites that orbit it, with a correspondingly much larger diameter. The

Earth–Moon system The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

is a unique exception in the Solar System; at 3,474 kilometres (2,158 miles) across, the Moon is 0.273 times the diameter of Earth and about of its mass. The next largest ratios are the

Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times ...

–

Triton Triton commonly refers to: * Triton (mythology), a Greek god * Triton (moon), a satellite of Neptune Triton may also refer to: Biology * Triton cockatoo, a parrot * Triton (gastropod), a group of sea snails * ''Triton'', a synonym of ''Triturus' ...

system at 0.055 (with a mass ratio of about 1 to 5000), the

Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...

–

Titan Titan most often refers to: * Titan (moon), the largest moon of Saturn * Titans, a race of deities in Greek mythology Titan or Titans may also refer to: Arts and entertainment Fictional entities Fictional locations * Titan in fiction, fictiona ...

system at 0.044 (with the second mass ratio next to the Earth–Moon system, 1 to 4250), the Jupiter– Ganymede system at 0.038, and the Uranus– Titania system at 0.031. For the category of dwarf planets,

Charon In Greek mythology, Charon or Kharon (; grc, Χάρων) is a psychopomp, the ferryman of Hades, the Greek underworld. He carries the souls of those who have been given funeral rites across the rivers Acheron and Styx, which separate the wo ...

has the largest ratio, being 0.52 the diameter and 12.2% the mass of Pluto.

Terminology

The first known natural satellite was the Moon, but it was considered a "planet" until Copernicus' introduction of '' De revolutionibus orbium coelestium'' in 1543. Until the discovery of the Galilean satellites in 1610 there was no opportunity for referring to such objects as a class.

Galileo Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642) was an Italian astronomer, physicist and engineer, sometimes described as a polymath. Commonly referred to as Galileo, his name was pronounced (, ). He was ...

chose to refer to his discoveries as ''Planetæ'' ("planets"), but later discoverers chose other terms to distinguish them from the objects they orbited. The first to use the term ''satellite'' to describe orbiting bodies was the German astronomer

Johannes Kepler Johannes Kepler (; ; 27 December 1571 – 15 November 1630) was a German astronomer, mathematician, astrologer, natural philosopher and writer on music. He is a key figure in the 17th-century Scientific Revolution, best known for his laws ...

in his pamphlet ''Narratio de Observatis a se quatuor Iouis satellitibus erronibus'' ("Narration About Four Satellites of Jupiter Observed") in 1610. He derived the term from the Latin word ''satelles'', meaning "guard", "attendant", or "companion", because the ''satellites'' accompanied their primary planet in their journey through the heavens. The term ''satellite'' thus became the normal one for referring to an object orbiting a planet, as it avoided the ambiguity of "moon". In 1957, however, the launching of the artificial object

Sputnik Sputnik 1 (; see § Etymology) was the first artificial Earth satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957 as part of the Soviet space program. It sent a radio signal back to Earth for t ...

created a need for new terminology. The terms ''man-made satellite'' and ''artificial moon'' were very quickly abandoned in favor of the simpler ''satellite'', and as a consequence, the term has become linked primarily with artificial objects flown in space. Because of this shift in meaning, the term ''moon'', which had continued to be used in a generic sense in works of popular science and in fiction, has regained respectability and is now used interchangeably with ''natural satellite'', even in scientific articles. When it is necessary to avoid both the ambiguity of confusion with Earth's natural satellite the Moon and the natural satellites of the other planets on the one hand, and artificial satellites on the other, the term ''natural satellite'' (using "natural" in a sense opposed to "artificial") is used. To further avoid ambiguity, the convention is to capitalize the word Moon when referring to Earth's natural satellite (a proper noun), but not when referring to other natural satellites ( common nouns). Many authors define "satellite" or "natural satellite" as orbiting some planet or minor planet, synonymous with "moon" – by such a definition all natural satellites are moons, but Earth and other planets are not satellites. A few recent authors define "moon" as "a satellite of a planet or minor planet", and "planet" as "a satellite of a star" – such authors consider Earth as a "natural satellite of the Sun".

Definition of a moon

There is no established lower limit on what is considered a "moon". Every natural celestial body with an identified orbit around a planet of the Solar System, some as small as a kilometer across, has been considered a moon, though objects a tenth that size within Saturn's rings, which have not been directly observed, have been called '' moonlets''. Small asteroid moons (natural satellites of asteroids), such as

Dactyl Dactyl may refer to: * Dactyl (mythology), a legendary being * Dactyl (poetry), a metrical unit of verse * Dactyl Foundation, an arts organization * Finger, a part of the hand * Dactylus, part of a decapod crustacean * "-dactyl", a suffix used ...

, have also been called moonlets. The upper limit is also vague. Two orbiting bodies are sometimes described as a double planet rather than primary and satellite.

Asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

s such as

90 Antiope Antiope (minor planet designation: 90 Antiope) is a double asteroid in the outer asteroid belt. It was discovered on October 1, 1866, by Robert Luther. In 2000, it was found to consist of two almost-equally-sized bodies orbiting each other. At a ...

are considered double asteroids, but they have not forced a clear definition of what constitutes a moon. Some authors consider the Pluto–Charon system to be a double (dwarf) planet. The most common dividing line on what is considered a moon rests upon whether the

barycentre In astronomy, the barycenter (or barycentre; ) is the center of mass of two or more bodies that orbit one another and is the point about which the bodies orbit. A barycenter is a dynamical point, not a physical object. It is an important co ...

is below the surface of the larger body, though this is somewhat arbitrary, because it depends on distance as well as relative mass.

Origin and orbital characteristics

The natural satellites orbiting relatively close to the planet on prograde, uninclined circular orbits ( ''regular'' satellites) are generally thought to have been formed out of the same collapsing region of the protoplanetary disk that created its primary. In contrast, irregular satellites (generally orbiting on distant,

inclined Incline, inclined, inclining, or inclination may refer to: *Grade (slope), the tilt, steepness, or angle from horizontal of a topographic feature (hillside, meadow, etc.) or constructed element (road, railway, field, etc.) *Slope, the tilt, steepn ...

eccentric Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...

and/or retrograde orbits) are thought to be captured

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

s possibly further fragmented by collisions. Most of the major natural satellites of the Solar System have regular orbits, while most of the small natural satellites have irregular orbits. The Moon and possibly

are exceptions among large bodies in that they are thought to have originated by the collision of two large proto-planetary objects (see the giant impact hypothesis). The material that would have been placed in orbit around the central body is predicted to have reaccreted to form one or more orbiting natural satellites. As opposed to planetary-sized bodies,

asteroid moon A minor-planet moon is an astronomical object that orbits a minor planet as its natural satellite. , there are 457 minor planets known or suspected to have moons. Discoveries of minor-planet moons (and binary objects, in general) are important ...

s are thought to commonly form by this process.

is another exception; although large and in a close, circular orbit, its motion is retrograde and it is thought to be a captured dwarf planet.

Temporary satellites

The capture of an asteroid from a heliocentric orbit is not always permanent. According to simulations,

temporary satellite A temporary satellite is an object which has been captured by the gravitational field of a planet and thus has become the planet's natural satellite, but, unlike irregular moons of the larger outer planets of the Solar System, will eventually either ...

s should be a common phenomenon. The only observed examples are , , . was a temporary satellite of Earth for nine months in 2006 and 2007.

Tidal locking

Most regular moons (natural satellites following relatively close and prograde orbits with small orbital inclination and eccentricity) in the Solar System are tidally locked to their respective primaries, meaning that the same side of the natural satellite always faces its planet. This phenomenon comes about through a loss of energy due to tidal forces raised by the planet, slowing the rotation of the satellite until it is negligible. The only known exception is

's natural satellite

Hyperion Hyperion may refer to: Greek mythology * Hyperion (Titan), one of the twelve Titans * ''Hyperion'', a byname of the Sun, Helios * Hyperion of Troy or Yperion, son of King Priam Science * Hyperion (moon), a moon of the planet Saturn * ''Hyp ...

, which rotates chaotically because of the gravitational influence of

. In contrast, the outer natural satellites of the giant planets (irregular satellites) are too far away to have become locked. For example, Jupiter's Himalia, Saturn's Phoebe, and Neptune's Nereid have rotation periods in the range of ten hours, whereas their orbital periods are hundreds of days.

Satellites of satellites

No "moons of moons" or subsatellites (natural satellites that orbit a natural satellite of a planet) are currently known. In most cases, the tidal effects of the planet would make such a system unstable. However, calculations performed after the 2008 detection of a possible ring system around Saturn's moon Rhea indicate that satellites orbiting Rhea could have stable orbits. Furthermore, the suspected rings are thought to be narrow, a phenomenon normally associated with

shepherd moon A shepherd moon (also herder moon or watcher moon) is a small natural satellite that clears a gap in planetary-ring material or keeps particles within a ring contained. The name is a result of the fact they limit the "herd" of the ring particle ...

s. However, targeted images taken by the '' Cassini'' spacecraft failed to detect rings around Rhea. It has also been proposed that Saturn's moon

Iapetus In Greek mythology, Iapetus (; ; grc, Ἰαπετός, Iapetós), also Japetus, is a Titan, the son of Uranus and Gaia and father of Atlas, Prometheus, Epimetheus, and Menoetius. He was also called the father of Buphagus and Anchiale in other ...

had a satellite in the past; this is one of several hypotheses that have been put forward to account for its

equatorial ridge Equatorial ridges are a feature of at least three of Saturn's moons: the large moon Iapetus and the tiny moons Atlas and Pan. They are ridges that closely follow the moons' equators. They appear to be unique to the Saturnian system, but it i ...

. Light-curve analysis suggests that Saturn's irregular satellite Kiviuq is extremely prolate, and is likely a

contact binary In astronomy, a contact binary is a binary star system whose component stars are so close that they touch each other or have merged to share their gaseous envelopes. A binary system whose stars share an envelope may also be called an overcontac ...

or even a binary moon.

Trojan satellites

Two natural satellites are known to have small companions at both their and

Lagrangian point In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of th ...

s, sixty degrees ahead and behind the body in its orbit. These companions are called trojan moons, as their orbits are analogous to the

trojan asteroid In astronomy, a trojan is a small celestial body (mostly asteroids) that shares the orbit of a larger body, remaining in a stable orbit approximately 60° ahead of or behind the main body near one of its Lagrangian points and . Trojans can sha ...

s of Jupiter. The trojan moons are Telesto and Calypso, which are the leading and following companions, respectively, of the Saturnian moon Tethys; and Helene and Polydeuces, the leading and following companions of the Saturnian moon

Dione Dione may refer to: Astronomy *106 Dione, a large main belt asteroid *Dione (moon), a moon of Saturn *Helene (moon), a moon of Saturn sometimes referred to as "Dione B" Mythology *Dione (Titaness), a Titaness in Greek mythology *Dione (mythology) ...

Asteroid satellites

The discovery of

243 Ida Ida, minor planet designation 243 Ida, is an asteroid in the Koronis family of the asteroid belt. It was discovered on 29 September 1884 by Austrian astronomer Johann Palisa at Vienna Observatory and named after a nymph from Greek mythology. ...

's natural satellite

in the early 1990s confirmed that some

s have natural satellites; indeed,

87 Sylvia Sylvia (minor planet designation: 87 Sylvia) is the one of the largest asteroids (approximately tied for 7th place, to within measurement uncertainties). It is the parent body of the Sylvia family and member of Cybele group located beyond the m ...

has two. Some, such as

, are double asteroids with two comparably sized components.

Shape

Neptune's moon Proteus is the largest irregularly shaped natural satellite; the shapes of Eris' moon Dysnomia and Orcus' moon Vanth are unknown. All other known natural satellites that are at least the size of Uranus's Miranda have lapsed into rounded

ellipsoid An ellipsoid is a surface that may be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation. An ellipsoid is a quadric surface; that is, a surface that may be defined as the ...

s under hydrostatic equilibrium, i.e. are "round/rounded satellites" and are sometimes categorized as planetary-mass moons. (Dysnomia's density is known to be high enough that it is probably a solid ellipsoid as well.) The larger natural satellites, being tidally locked, tend toward

ovoid An oval () is a closed curve in a plane which resembles the outline of an egg. The term is not very specific, but in some areas (projective geometry, technical drawing, etc.) it is given a more precise definition, which may include either one or ...

(egg-like) shapes: squat at their poles and with longer equatorial axes in the direction of their primaries (their planets) than in the direction of their motion. Saturn's moon

Mimas Mimas may refer to: *Mimas (Giant), son of Gaia in Greek mythology, one of the Gigantes * Mimas (''Aeneid''), a son of Amycus and Theono, born the same night as Paris, who escorted Aeneas to Italy *Karaburun, a town and district in Turkey, formerl ...

, for example, has a major axis 9% greater than its polar axis and 5% greater than its other equatorial axis. Methone, another of Saturn's moons, is only around 3 km in diameter and visibly egg-shaped. The effect is smaller on the largest natural satellites, where their own gravity is greater relative to the effects of tidal distortion, especially those that orbit less massive planets or, as in the case of the Moon, at greater distances.

Geological activity

Of the twenty known natural satellites in the Solar System that are large enough to be gravitationally rounded, several remain geologically active today. Io is the most volcanically active body in the Solar System, while

Europa Europa may refer to: Places * Europe * Europa (Roman province), a province within the Diocese of Thrace * Europa (Seville Metro), Seville, Spain; a station on the Seville Metro * Europa City, Paris, France; a planned development * Europa Cliff ...

, Enceladus,

and

display evidence of ongoing tectonic activity and cryovolcanism. In the first three cases, the geological activity is powered by the tidal heating resulting from having eccentric orbits close to their giant-planet primaries. (This mechanism would have also operated on Triton in the past, before its orbit was circularized.) Many other natural satellites, such as Earth's Moon, Ganymede, Tethys and Miranda, show evidence of past geological activity, resulting from energy sources such as the

decay Decay may refer to: Science and technology * Bit decay, in computing * Software decay, in computing * Distance decay, in geography * Decay time (fall time), in electronics Biology * Decomposition of organic matter * Tooth decay (dental caries) ...

of their

primordial Primordial may refer to: * Primordial era, an era after the Big Bang. See Chronology of the universe * Primordial sea (a.k.a. primordial ocean, ooze or soup). See Abiogenesis * Primordial nuclide, nuclides, a few radioactive, that formed before ...

radioisotopes, greater past orbital eccentricities (due in some cases to past orbital resonances), or the differentiation or freezing of their interiors. Enceladus and Triton both have active features resembling geysers, although in the case of Triton solar heating appears to provide the energy. Titan and Triton have significant atmospheres; Titan also has hydrocarbon lakes. Also Io and Callisto have atmospheres, even if they are extremely thin.A moon with atmosphere , The Planetary Society
/ref> Four of the largest natural satellites, Europa, Ganymede, Callisto, and Titan, are thought to have subsurface oceans of liquid water, while smaller Enceladus may have localized subsurface liquid water.

Occurrence in the Solar System

Euler-Diagram bodies in the Solar System

Beside planets and dwarf planets objects within our Solar System known to have natural satellites are 76 in the asteroid belt (five with two each), four

Jupiter trojan The Jupiter trojans, commonly called trojan asteroids or simply trojans, are a large group of asteroids that share the planet Jupiter's orbit around the Sun. Relative to Jupiter, each trojan librates around one of Jupiter's stable Lagrange poin ...

s, 39 near-Earth objects (two with two satellites each), and 14 Mars-crossers. There are also 84 known natural satellites of trans-Neptunian objects. Some 150 additional small bodies have been observed within the rings of Saturn, but only a few were tracked long enough to establish orbits. Planets around other stars are likely to have satellites as well, and although numerous candidates have been detected to date, none have yet been confirmed. Of the inner planets,

Mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

and Venus have no natural satellites; Earth has one large natural satellite, known as the Moon; and Mars has two tiny natural satellites, Phobos and

Deimos Deimos, a Greek word for ''dread'', may refer to: * Deimos (deity), one of the sons of Ares and Aphrodite in Greek mythology * Deimos (moon), the smaller and outermost of Mars' two natural satellites * Elecnor Deimos, a Spanish aerospace company * ...

. The giant planets have extensive systems of natural satellites, including half a dozen comparable in size to Earth's Moon: the four

Galilean moon The Galilean moons (), or Galilean satellites, are the four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto. They were first seen by Galileo Galilei in December 1609 or January 1610, and recognized by him as satellites of Jupiter ...

s, Saturn's Titan, and

's Triton. Saturn has an additional six mid-sized natural satellites massive enough to have achieved hydrostatic equilibrium, and Uranus has five. It has been suggested that some satellites may potentially harbour life. Among the objects generally agreed by astronomers to be dwarf planets,

Ceres Ceres most commonly refers to: * Ceres (dwarf planet), the largest asteroid * Ceres (mythology), the Roman goddess of agriculture Ceres may also refer to: Places Brazil * Ceres, Goiás, Brazil * Ceres Microregion, in north-central Goiás st ...

and have no known natural satellites. Pluto has the relatively large natural satellite Charon and four smaller natural satellites;

Styx In Greek mythology, Styx (; grc, Στύξ ) is a river that forms the boundary between Earth (Gaia) and the Underworld. The rivers Acheron, Cocytus, Lethe, Phlegethon, and Styx all converge at the centre of the underworld on a great marsh, whic ...

Nix Nix or NIX may refer to: Places * Nix, Alabama, an unincorporated community, United States * Nix, Texas, a ghost town in southwestern Lampasas County, Texas, United States * Nix (moon), a moon of Pluto People * Nix (surname), listing people with ...

, Kerberos, and

Hydra Hydra generally refers to: * Lernaean Hydra, a many-headed serpent in Greek mythology * ''Hydra'' (genus), a genus of simple freshwater animals belonging to the phylum Cnidaria Hydra or The Hydra may also refer to: Astronomy * Hydra (constel ...

. Haumea has two natural satellites; , , Makemake, , and have one each. The Pluto–Charon system is unusual in that the

center of mass In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force may ...

lies in open space between the two, a characteristic sometimes associated with a double-planet system. The seven largest

natural satellites A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are often colloquially referred to as ''moons'' ...

in the Solar System (those bigger than 2,500 km across) are Jupiter's

s (Ganymede, Callisto, Io, and

), Saturn's moon Titan, Earth's moon, and Neptune's captured natural satellite Triton. Triton, the smallest of these, has more mass than all smaller natural satellites together. Similarly in the next size group of nine mid-sized natural satellites, between 1,000 km and 1,600 km across, Titania, Oberon, Rhea,

, Charon, Ariel, Umbriel,

, and Tethys, the smallest, Tethys, has more mass than all smaller natural satellites together. As well as the natural satellites of the various planets, there are also over 80 known natural satellites of the dwarf planets, minor planets and other small Solar System bodies. Some studies estimate that up to 15% of all trans-Neptunian objects could have satellites. The following is a comparative table classifying the natural satellites in the Solar System by diameter. The column on the right includes some notable planets, dwarf planets, asteroids, and trans-Neptunian objects for comparison. The natural satellites of the planets are named after mythological figures. These are predominantly Greek, except for the Uranian natural satellites, which are named after Shakespearean characters. The twenty satellites massive enough to be round are in bold in the table below. Minor planets and satellites where there is disagreement in the literature on roundness are italicized in the table below.

Visual summary

Ganymede - Perijove 34 Composite.png, Ganymede
(moon of Jupiter) Titan in true color.jpg,

(moon of Saturn) Callisto.jpg, Callisto
(moon of Jupiter) Io highest resolution true color.jpg, Io
(moon of Jupiter) FullMoon2010.jpg, Moon
(moon of Earth) Europa-moon-with-margins.jpg,

(moon of Jupiter) Triton moon mosaic Voyager 2 (large).jpg,

(moon of Neptune) Titania (moon) color cropped.jpg, Titania
(moon of Uranus) PIA07763 Rhea full globe5.jpg, Rhea
(moon of Saturn) Voyager 2 picture of Oberon.jpg, Oberon
(moon of Uranus) Iapetus as seen by the Cassini probe - 20071008.jpg,

(moon of Saturn) Charon in True Color - High-Res.jpg,

(moon of Pluto) PIA00040_Umbrielx2.47.jpg, Umbriel
(moon of Uranus) Ariel (moon).jpg, Ariel
(moon of Uranus) Dione in natural light.jpg,

(moon of Saturn) PIA18317-SaturnMoon-Tethys-Cassini-20150411.jpg, Tethys
(moon of Saturn) PIA17202 - Approaching Enceladus.jpg, Enceladus
(moon of Saturn) PIA18185 Miranda's Icy Face.jpg, Miranda
(moon of Uranus) Proteus (Voyager 2).jpg, Proteus
(moon of Neptune) Mimas Cassini.jpg,

(moon of Saturn) Hyperion true.jpg,

(moon of Saturn) Phoebe cassini.jpg, Phoebe
(moon of Saturn) Larissa 1.jpg,

Larissa Larissa (; el, Λάρισα, , ) is the capital and largest city of the Thessaly region in Greece. It is the fifth-most populous city in Greece with a population of 144,651 according to the 2011 census. It is also capital of the Larissa regiona ...

(moon of Neptune) PIA12714 Janus crop.jpg,

Janus In ancient Roman religion and myth, Janus ( ; la, Ianvs ) is the god of beginnings, gates, transitions, time, duality, doorways, passages, frames, and endings. He is usually depicted as having two faces. The month of January is named for Janu ...

(moon of Saturn) Amalthea_(moon).png, Amalthea
(moon of Jupiter) Puck.png, Puck
(moon of Uranus) PIA09813 Epimetheus S. polar region.jpg, Epimetheus
(moon of Saturn) Thebe.jpg,

Thebe Thebe may refer to: * Any of several female characters in Greek mythology - see List of mythological figures named Thebe * Thebe (moon), a moon of Jupiter * Thebe (currency), 1/100 of a Botswana pula * Thebe, an Amazons, Amazon * Thebe, alternate ...

(moon of Jupiter) Prometheus 12-26-09a.jpg, Prometheus
(moon of Saturn) PIA21055 - Pandora Up Close.jpg,

Pandora In Greek mythology, Pandora (Greek: , derived from , ''pān'', i.e. "all" and , ''dōron'', i.e. "gift", thus "the all-endowed", "all-gifted" or "all-giving") was the first human woman created by Hephaestus on the instructions of Zeus. As Hes ...

(moon of Saturn) Hydra Enhanced Color.jpg,

(moon of Pluto) Nix best view.jpg,

(moon of Pluto) Leading hemisphere of Helene - 20110618.jpg, Helene
(moon of Saturn) Atlas (NASA).jpg, Atlas
(moon of Saturn) Pan by Cassini, March 2017.jpg, Pan
(moon of Saturn) Telesto cassini closeup.jpg, Telesto
(moon of Saturn) Calypso N1644755236 1.jpg, Calypso
(moon of Saturn) Phobos colour 2008.jpg, Phobos
(moon of Mars) Deimos-MRO.jpg,

(moon of Mars) Daphnis (Saturn's Moon).jpg, Daphnis
(moon of Saturn) Methone PIA14633.jpg, Methone
(moon of Saturn) Dactyl-HiRes.jpg,

(moon of

Ida Ida or IDA may refer to: Astronomy * Ida Facula, a mountain on Amalthea, a moon of Jupiter *243 Ida, an asteroid *International Docking Adapter, a docking adapter for the International Space Station Computing *Intel Dynamic Acceleration, a techn ...

) Stacked image of Dimorphos true orientation.jpg,

Dimorphos (65803) Didymos I Dimorphos (provisional designation S/2003 (65803) 1) is a minor-planet moon of the near-Earth asteroid 65803 Didymos, with which it forms a binary system. It has a diameter of and has been characterised as a low-density rubb ...

(moon of Didymos) Moons of the Solar System To Scale (43564841545)

References

External links

All moons

Natural Satellite Physical Parameters
(JPL-NASA, with refs – last updated July 2006)

(The Planetary Society, as of March 2009)
The JPL's Solar System Dynamics page
*
Planetary Names: Planet and Satellite Names and Discoverers

"Upper size limit for moons explained"
Kelly Young. ''Nature'' (vol 441, p. 834) 14 June 2006

Album
of moon images by Kevin M. Gill
The Atlas of Moons
by the National Geographic Society

Jupiter's moons

*

Scott S. Sheppard

Scott S. Sheppard

Saturn's moons

Satellite-hunters find four new moons of the planet Saturn
David Brand , 26 October 2000

Scott S. Sheppard {{DEFAULTSORT:Natural Satellite