The Info List - Galilean Moons

The Galilean moons
Galilean moons
are the four largest moons of Jupiter—Io, Europa, Ganymede, and Callisto. They were first seen by Galileo Galilei
Galileo Galilei
in January 1610, and recognized by him as satellites of Jupiter
in March 1610.[1] They are the first objects found to orbit another planet. Their names derive from the lovers of Zeus. They are among the largest objects in the Solar System
Solar System
with the exception of the Sun
and the eight planets, with a radius larger than any of the dwarf planets. Ganymede is the largest moon in the Solar System, and is even bigger than the planet Mercury. The three inner moons—Io, Europa, and Ganymede—are in a 4:2:1 orbital resonance with each other. Because of their much smaller size, and therefore weaker self-gravitation, all of Jupiter's remaining moons have irregular forms rather than a spherical shape. The Galilean moons
Galilean moons
were discovered in either 1609 or 1610 when Galileo made improvements to his telescope, which enabled him to observe celestial bodies more distinctly than ever.[2] Galileo's discovery showed the importance of the telescope as a tool for astronomers by proving that there were objects in space that cannot be seen by the naked eye. More importantly, the incontrovertible discovery of celestial bodies orbiting something other than Earth
dealt a serious blow to the then-accepted Ptolemaic world system, or the geocentric theory in which everything orbits around Earth. Galileo initially named his discovery the Cosmica Sidera ("Cosimo's stars"), but the names that eventually prevailed were chosen by Simon Marius. Marius discovered the moons independently at the same time as Galileo, and gave them their present names, which were suggested by Johannes Kepler, in his Mundus Jovialis, published in 1614.[3]


1 History

1.1 Discovery 1.2 Dedication to the Medicis 1.3 Name 1.4 Determination of longitude

2 Members

2.1 Io 2.2 Europa 2.3 Ganymede 2.4 Callisto

3 Comparative structure

3.1 Size 3.2 Latest flyby

4 Origin and evolution 5 Visibility 6 Orbit animation 7 See also 8 References 9 External links

History[edit] Discovery[edit]

Galileo Galilei, the discoverer of the four moons

As a result of improvements Galileo Galilei
Galileo Galilei
made to the telescope, with a magnifying capability of 20×,[4] he was able to see celestial bodies more distinctly than was ever possible before. This allowed Galilei to discover in either December 1609 or January 1610 what came to be known as the Galilean moons.[2][5] On January 7, 1610, Galileo wrote a letter containing the first mention of Jupiter's moons. At the time, he saw only three of them, and he believed them to be fixed stars near Jupiter. He continued to observe these celestial orbs from January 8 to March 2, 1610. In these observations, he discovered a fourth body, and also observed that the four were not fixed stars, but rather were orbiting Jupiter.[2] Galileo's discovery proved the importance of the telescope as a tool for astronomers by showing that there were objects in space to be discovered that until then had remained unseen by the naked eye. More importantly, the discovery of celestial bodies orbiting something other than Earth
dealt a blow to the then-accepted Ptolemaic world system, which held that Earth
was at the center of the universe and all other celestial bodies revolved around it.[6] Galileo's Sidereus Nuncius (Starry Messenger), which announced celestial observations through his telescope, does not explicitly mention Copernican heliocentrism, a theory that placed the Sun
at the center of the universe. Nevertheless, Galileo accepted the Copernican theory.[2] A Chinese historian of astronomy, Xi Zezong, has claimed that a "small reddish star" observed near Jupiter
in 362 BCE by Chinese astronomer Gan De may have been Ganymede, predating Galileo's discovery by around two millennia.[7] Dedication to the Medicis[edit]

The Medician stars in the Sidereus Nuncius
Sidereus Nuncius
(the 'starry messenger'), 1610. The moons are drawn in changing positions.

In 1605, Galileo had been employed as a mathematics tutor for Cosimo de' Medici. In 1609, Cosimo became Grand Duke Cosimo II of Tuscany. Galileo, seeking patronage from his now-wealthy former student and his powerful family, used the discovery of Jupiter's moons to gain it.[2] On February 13, 1610, Galileo wrote to the Grand Duke's secretary:

"God graced me with being able, through such a singular sign, to reveal to my Lord my devotion and the desire I have that his glorious name live as equal among the stars, and since it is up to me, the first discoverer, to name these new planets, I wish, in imitation of the great sages who placed the most excellent heroes of that age among the stars, to inscribe these with the name of the Most Serene Grand Duke."[2]

Galileo asked whether he should name the moons the "Cosmian Stars", after Cosimo alone, or the "Medician Stars", which would honor all four brothers in the Medici clan. The secretary replied that the latter name would be best.[2] On March 12, 1610, Galileo wrote his dedicatory letter to the Duke of Tuscany, and the next day sent a copy to the Grand Duke, hoping to obtain the Grand Duke's support as quickly as possible. On March 19, he sent the telescope he had used to first view Jupiter's moons to the Grand Duke, along with an official copy of Sidereus Nuncius
Sidereus Nuncius
(The Starry Messenger) that, following the secretary's advice, named the four moons the Medician Stars.[2] In his dedicatory introduction, Galileo wrote:

Scarcely have the immortal graces of your soul begun to shine forth on earth than bright stars offer themselves in the heavens which, like tongues, will speak of and celebrate your most excellent virtues for all time. Behold, therefore, four stars reserved for your illustrious name ... which ... make their journeys and orbits with a marvelous speed around the star of Jupiter
... like children of the same family ... Indeed, it appears the Maker of the Stars himself, by clear arguments, admonished me to call these new planets by the illustrious name of Your Highness before all others.[2]


A Jovilabe:[8] an apparatus from the mid-18th century for demonstrating the orbits of Jupiter's satellites

Galileo initially called his discovery the Cosmica Sidera ("Cosimo's stars"), in honour of Cosimo II de' Medici
Cosimo II de' Medici
(1590–1621).[9] At Cosimo's suggestion, Galileo changed the name to Medicea Sidera ("the Medician stars"), honouring all four Medici brothers (Cosimo, Francesco, Carlo, and Lorenzo). The discovery was announced in the Sidereus Nuncius
Sidereus Nuncius
("Starry Messenger"), published in Venice
in March 1610, less than two months after the first observations. Other names put forward include:

I. Principharus (for the "prince" of Tuscany), II. Victripharus (after Vittoria della Rovere), III. Cosmipharus (after Cosimo de' Medici) and IV. Fernipharus (after Duke Ferdinando de' Medici)[10] – by Giovanni Battista Hodierna, a disciple of Galileo and author of the first ephemerides (Medicaeorum Ephemerides, 1656); Circulatores Jovis, or Jovis Comites – by Johannes Hevelius; Gardes, or Satellites (from the Latin satelles, satellitis, meaning "escorts") – by Jacques Ozanam.

The names that eventually prevailed were chosen by Simon Marius, who discovered the moons independently at the same time as Galileo: he named them at the suggestion of Johannes Kepler
Johannes Kepler
after lovers of the god Zeus
(the Greek equivalent of Jupiter): Io, Europa, Ganymede and Callisto, in his Mundus Jovialis, published in 1614.[11] Galileo steadfastly refused to use Marius' names and invented as a result the numbering scheme that is still used nowadays, in parallel with proper moon names. The numbers run from Jupiter
outward, thus I, II, III and IV for Io, Europa, Ganymede, and Callisto respectively.[11] Galileo used this system in his notebooks but never actually published it. The numbered names ( Jupiter
x) were used until the mid-20th century when other inner moons were discovered, and Marius' names became widely used.[11] Determination of longitude[edit] See also: History of longitude Galileo was able to develop a method of determining longitude based on the timing of the orbits of the Galilean moons.[12] The times of the eclipses of the moons could be precisely calculated in advance, and compared with local observations on land or on ship to determine the local time and hence longitude. The main problem with the technique was that it was difficult to observe the Galilean moons
Galilean moons
through a telescope on a moving ship; a problem that Galileo tried to solve with the invention of the celatone. The method was used by Cassini and Picard to re-map France.[13] Members[edit] Some models predict that there may have been several generations of Galilean satellites in Jupiter's early history. Each generation of moons to have formed would have spiraled into Jupiter
and been destroyed, due to tidal interactions with Jupiter's proto-satellite disk, with new moons forming from the remaining debris. By the time the present generation formed, the gas in the proto-satellite disk had thinned out to the point that it no longer greatly interfered with the moons' orbits.[14][15] Other models suggest that Galilean satellites formed in a proto-satellite disk, in which formation timescales were comparable to or shorter than orbital migration timescales.[16] Io is anhydrous and likely has an interior of rock and metal.[14] Europa is thought to contain 8% ice and water by mass with the remainder rock.[14] These moons are, in increasing order of distance from Jupiter:

Name Image Model of interior I E G C Diameter (km) Mass (kg) Density (g/cm³) Semi-major axis (km)[17] Orbital period(d) [18] (relative) Inclination (°)[19] Eccentricity

Io Jupiter

7003366000000000000♠3660.0 7003363740000000000♠× 3637.4 7003363060000000000♠× 3630.6 0893 !7022893000000000000♠8.93×1022 7000352800000000000♠3.528 7005421800000000000♠421800 1.769

(1) 0.050 0.0041

Europa Jupiter

7003312160000000000♠3121.6 0480 !7022480000000000000♠4.8×1022 3.014 7005671100000000000♠671100 3.551

(2) 0.471 0.0094

Ganymede Jupiter

7003526820000000000♠5268.2 1480 !7023148000000000000♠1.48×1023 1.942 7006107040000000000♠1070400 7.155

(4) 0.204 0.0011

Callisto Jupiter

7003482060000000000♠4820.6 1080 !7023108000000000000♠1.08×1023 1.834 7006188270000000000♠1882700 16.69

(9.4) 0.205 0.0074

Further information: Moons of Jupiter Io[edit] Main article: Io (moon)

Tupan Patera
Tupan Patera
on Io

Io ( Jupiter
I) is the innermost of the four Galilean moons
Galilean moons
of Jupiter and, with a diameter of 3642 kilometers, the fourth-largest moon in the Solar System. It was named after Io, a priestess of Hera
who became one of the lovers of Zeus. Nevertheless, it was simply referred to as " Jupiter
I", or "The first satellite of Jupiter", until the mid-20th century.[11] With over 400 active volcanos, Io is the most geologically active object in the Solar System.[20] Its surface is dotted with more than 100 mountains, some of which are taller than Earth's Mount Everest.[21] Unlike most satellites in the outer Solar System
Solar System
(which have a thick coating of ice), Io is primarily composed of silicate rock surrounding a molten iron or iron sulfide core. Although not proven, recent data from the Galileo orbiter indicate that Io might have its own magnetic field.[22] Io has an extremely thin atmosphere made up mostly of sulfur dioxide (SO2).[23] If a surface data or collection vessel were to land on Io in the future, it would have to be extremely tough (similar to the tank-like bodies of the Soviet Venera
landers) to survive the radiation and magnetic fields that originate from Jupiter.[24] Europa[edit] Main article: Europa (moon)


Europa ( Jupiter
II), the second of the four Galilean moons, is the second closest to Jupiter
and the smallest at 3121.6 kilometers in diameter, which is slightly smaller than the Moon. The name comes from a mythical Phoenician noblewoman, Europa, who was courted by Zeus
and became the queen of Crete, though the name did not become widely used until the mid-20th century.[11] It has a smooth and bright surface,[25] with a layer of water surrounding the mantle of the planet, thought to be 100 kilometers thick.[26] The smooth surface includes a layer of ice, while the bottom of the ice is theorized to be liquid water.[27] The apparent youth and smoothness of the surface have led to the hypothesis that a water ocean exists beneath it, which could conceivably serve as an abode for extraterrestrial life.[28] Heat energy from tidal flexing ensures that the ocean remains liquid and drives geological activity.[29] Life may exist in Europa's under-ice ocean, perhaps subsisting in an environment similar to Earth's deep-ocean hydrothermal vents or the Antarctic Lake Vostok.[30] Life in such an ocean could possibly be similar to microbial life on Earth
in the deep ocean.[31] So far, there is no evidence that life exists on Europa, but the likely presence of liquid water has spurred calls to send a probe there.[32]

Recurring plume erupting from Europa.[33]

The prominent markings that criss-cross the moon seem to be mainly albedo features, which emphasize low topography. There are few craters on Europa because its surface is tectonically active and young.[34] Some theories suggest that Jupiter's gravity is causing these markings, as one side of Europa is constantly facing Jupiter. Also, volcanic water eruptions splitting the surface of Europa, and even geysers have been considered as a cause. The color of the markings, reddish-brown, is theorized to be caused by sulfur, but scientists cannot confirm that, because no data collection devices have been sent to Europa.[35] Europa is primarily made of silicate rock and likely has an iron core. It has a tenuous atmosphere composed primarily of oxygen. Ganymede[edit] Main article: Ganymede (moon)


Ganymede ( Jupiter
III), the third Galilean moon is named after the mythological Ganymede, cupbearer of the Greek gods and Zeus's beloved.[36] Ganymede is the largest natural satellite in the Solar System at 5262.4 kilometers in diameter, which makes it larger than the planet Mercury – although only at about half of its mass[37] since Ganymede is an icy world. It is the only satellite in the Solar System known to possess a magnetosphere, likely created through convection within the liquid iron core.[38] Ganymede is composed primarily of silicate rock and water ice, and a salt-water ocean is believed to exist nearly 200 km below Ganymede's surface, sandwiched between layers of ice.[39] The metallic core of Ganymede suggests a greater heat at some time in its past than had previously been proposed. The surface is a mix of two types of terrain—highly cratered dark regions and younger, but still ancient, regions with a large array of grooves and ridges. Ganymede has a high number of craters, but many are gone or barely visible due to its icy crust forming over them. The satellite has a thin oxygen atmosphere that includes O, O2, and possibly O3 (ozone), and some atomic hydrogen.[40][41] Callisto[edit] Main article: Callisto (moon)

Callisto's Valhalla impact crater as seen by Voyager

Callisto ( Jupiter
IV) is the fourth and last Galilean moon, and is the second largest of the four, and at 4820.6 kilometers in diameter, it is the third largest moon in the Solar System, and barely smaller than Mercury, though only a third of the latter's mass. It is named after the Greek mythological nymph Callisto, a lover of Zeus
who was a daughter of the Arkadian King Lykaon and a hunting companion of the goddess Artemis. The moon does not form part of the orbital resonance that affects three inner Galilean satellites and thus does not experience appreciable tidal heating.[42] Callisto is composed of approximately equal amounts of rock and ices, which makes it the least dense of the Galilean moons. It is one of the most heavily cratered satellites in the Solar System, and one major feature is a basin around 3000 km wide called Valhalla. Callisto is surrounded by an extremely thin atmosphere composed of carbon dioxide[43] and probably molecular oxygen.[44] Investigation revealed that Callisto may possibly have a subsurface ocean of liquid water at depths less than 300 kilometres.[45] The likely presence of an ocean within Callisto indicates that it can or could harbour life. However, this is less likely than on nearby Europa.[46] Callisto has long been considered the most suitable place for a human base for future exploration of the Jupiter
system since it is furthest from the intense radiation of Jupiter.[47] Comparative structure[edit]

Comparison of (a part of) Jupiter
and its four largest natural satellites

Jovian Radiation

Moon rem/day

Io 3600[48]

Europa 540[48]

Ganymede 8[48]

Callisto 0.01[48]

Fluctuations in the orbits of the moons indicate that their mean density decreases with distance from Jupiter. Callisto, the outermost and least dense of the four, has a density intermediate between ice and rock whereas Io, the innermost and densest moon, has a density intermediate between rock and iron. Callisto has an ancient, heavily cratered and unaltered ice surface and the way it rotates indicates that its density is equally distributed, suggesting that it has no rocky or metallic core but consists of a homogeneous mix of rock and ice. This may well have been the original structure of all the moons. The rotation of the three inner moons, in contrast, indicates differentiation of their interiors with denser matter at the core and lighter matter above. They also reveal significant alteration of the surface. Ganymede reveals past tectonic movement of the ice surface which required partial melting of subsurface layers. Europa reveals more dynamic and recent movement of this nature, suggesting a thinner ice crust. Finally, Io, the innermost moon, has a sulfur surface, active volcanism and no sign of ice. All this evidence suggests that the nearer a moon is to Jupiter
the hotter its interior. The current model is that the moons experience tidal heating as a result of the gravitational field of Jupiter
in inverse proportion to the square of their distance from the giant planet. In all but Callisto this will have melted the interior ice, allowing rock and iron to sink to the interior and water to cover the surface. In Ganymede a thick and solid ice crust then formed. In warmer Europa a thinner more easily broken crust formed. In Io the heating is so extreme that all the rock has melted and water has long ago boiled out into space.

Surface features of the four members at different levels of zoom in each row


Galilean moons
Galilean moons
compared with other Solar System
Solar System
bodies, although pixel scale is not accurate at this resolution.

Latest flyby[edit]

and Io





and Galilean moons
Galilean moons
circa 2007, imaged by New Horizons
New Horizons
during flyby. (greyscale colour)

Origin and evolution[edit]

The relative masses of the Jovian moons. Those smaller than Europa are not visible at this scale, and combined would only be visible at 100× magnification.

Jupiter's regular satellites are believed to have formed from a circumplanetary disk, a ring of accreting gas and solid debris analogous to a protoplanetary disk.[49][50] They may be the remnants of a score of Galilean-mass satellites that formed early in Jupiter's history.[15][49] Simulations suggest that, while the disk had a relatively high mass at any given moment, over time a substantial fraction (several tenths of a percent) of the mass of Jupiter
captured from the Solar nebula was processed through it. However, the disk mass of only 2% that of Jupiter
is required to explain the existing satellites.[49] Thus there may have been several generations of Galilean-mass satellites in Jupiter's early history. Each generation of moons would have spiraled into Jupiter, due to drag from the disk, with new moons then forming from the new debris captured from the Solar nebula.[49] By the time the present (possibly fifth) generation formed, the disk had thinned out to the point that it no longer greatly interfered with the moons' orbits.[15] The current Galilean moons
Galilean moons
were still affected, falling into and being partially protected by an orbital resonance which still exists for Io, Europa, and Ganymede. Ganymede's larger mass means that it would have migrated inward at a faster rate than Europa or Io.[49] Visibility[edit]

The Galilean moons
Galilean moons
seen with an amateur telescope.

and its Galilean moons
Galilean moons
Io, Ganymede, Europa, and Callisto (at maximum elongation) juxtaposed with the full moon during their conjunction on 10 April 2017.

All four Galilean moons
Galilean moons
are bright enough that they could be sighted from Earth
without a telescope, if they were farther away from Jupiter. (They are, however, easily visible with even low-powered binoculars.) They have apparent magnitudes between 4.6 and 5.6 when Jupiter
is in opposition with the Sun,[51] and are about one unit of magnitude dimmer when Jupiter
is in conjunction. The main difficulty in observing the moons from Earth
is their proximity to Jupiter
since they are obscured by its brightness.[52] The maximum angular separations of the moons are between 2 and 10 minutes of arc from Jupiter,[53] which is close to the limit of human visual acuity. Ganymede and Callisto, at their maximum separation, are the likeliest targets for potential naked-eye observation. Orbit animation[edit] GIF animation of the resonance of Io, Europa, and Ganymede

The three inner Galilean moons
Galilean moons
revolve in a 1:2:4 resonance.

See also[edit]


Moons of Jupiter Jupiter's moons in fiction Colonization of the Jovian System


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of Callisto". Journal of Geophysical Research. 110: E02003. Bibcode:2005JGRE..110.2003L. doi:10.1029/2004JE002322.  ^ Zimmer, C; Khurana, Krishan K.; Kivelson, Margaret G. (2000). "Subsurface Oceans on Europa and Callisto: Constraints from Galileo Magnetometer Observations" (PDF). Icarus. 147 (2): 329–47. Bibcode:2000Icar..147..329Z. doi:10.1006/icar.2000.6456.  ^ Lipps, Jere H.; Delory, Gregory; Pitman, Joseph T.; Rieboldt, Sarah (2004). "Astrobiology of Jupiter's icy moons". Instruments, Methods, and Missions for Astrobiology VIII. Instruments. Instruments, Methods, and Missions for Astrobiology VIII. 5555. p. 78. Bibcode:2004SPIE.5555...78L. doi:10.1117/12.560356.  ^ Trautman, Pat; Bethke, Kristen (2003). "Revolutionary Concepts for Human Outer Planet
Exploration(HOPE)" (PDF). NASA. Archived from the original (PDF) on 2012-01-19.  ^ a b c d Ringwald, Frederick A. (29 February 2000). "SPS 1020 (Introduction to Space Sciences)". California State University, Fresno. Archived from the original on 20 September 2009. Retrieved 5 January 2014.  ^ a b c d e Canup, Robert M.; Ward, William R. (2009). "Origin of Europa and the Galilean Satellites". Europa. University of Arizona Press. pp. 59–83. ISBN 978-0-8165-2844-8.  ^ Alibert, Y.; Mousis, O.; Benz, W. (2005). "Modeling the Jovian subnebula I. Thermodynamic conditions and migration of proto-satellites". Astronomy
& Astrophysics. 439 (3): 1205–13. arXiv:astro-ph/0505367 . Bibcode:2005A&A...439.1205A. doi:10.1051/0004-6361:20052841.  ^ Yeomans, Donald K. (2006-07-13). "Planetary Satellite Physical Parameters". JPL Solar System
Solar System
Dynamics. Retrieved 2008-08-23.  ^ Jupiter
is about 750 times brighter than Ganymede and about 2000 times brighter than Callisto. Ganymede: (5th root of 100)^(4.4 Ganymede APmag − (−2.8 Jup APmag)) = 758 Callisto: (5th root of 100)^(5.5 Callisto APmag − (−2.8 Jup APmag)) = 2089 ^ Jupiter
near perihelion 2010-Sep-19: 656.7 (Callisto angular separation arcsec) − 24.9 (jup angular radius arcsec) = 631 arcsec = 10 arcmin

External links[edit]

Animation of Galileo's observation, march 1613 Sky & Telescope
utility for identifying Galilean moons

Wikimedia Commons has media related to Moons of Jupiter.

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Moons of Jupiter

Listed in approximately increasing distance from Jupiter. Provisional designations in italics.

Inner moons

Metis Adrastea Amalthea Thebe

Galilean moons

Io Europa Ganymede Callisto

Themisto group


Himalia group

Leda Himalia Lysithea Elara Dia

Carpo group



S/2003 J 12


S/2011 J 1

Ananke group


Euanthe Iocaste Praxidike Harpalyke Thyone Ananke


LX(?) Jupiter
LII Thelxinoe S/2003 J 16 Mneme Hermippe

Carme group

Herse Kale Aitne Taygete S/2003 J 19(?) Chaldene Erinome Kallichore Kalyke Carme Pasithee Jupiter
LI Eukelade Arche Isonoe S/2003 J 9(?) Jupiter

Pasiphae group

Euporie Jupiter
LV Helike Orthosie Jupiter
LIV Jupiter
LVIII S/2003 J 10(?) S/2003 J 23(?) Aoede Callirrhoe Eurydome Kore Cyllene Jupiter
LVI Jupiter
LIX S/2003 J 4(?) Pasiphae Hegemone Sinope Sponde Autonoe Megaclite


S/2003 J 2

Rings of Jupiter In fiction

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Natural satellites of the Solar System

Planetary satellites

Terrestrial Martian Jovian Saturnian Uranian Neptunian

Other satellites

Minor-planet moons Plutonian Haumean Eridian Makemakean

Largest satellites (mean radius ≥ 100 km)



largest / 2634 km / 0.413 Earths

Titan Callisto Io Moon Europa Triton Titania Rhea Oberon Iapetus Charon Umbriel Ariel Dione Tethys [Dysnomia] Enceladus Miranda Proteus Mimas [Hi'iaka] Nereid Hyperion Phoebe

smallest / 106 km / 0.017 Earths


Ariel Callisto Charon Dione [Dysnomia] Enceladus Europa Ganymede [Hi'iaka] Hyperion Iapetus Io Mimas Miranda Moon Nereid Oberon Phoebe Proteus Rhea Tethys Titan Titania Triton Umbriel

Discovery timeline Inner moons Irregular moons List Naming Regular moons Trojan moons NOTE: Italicized moons are not close to being in hydrostatic equilibrium; [bracketed] moons may or may not be close to being in hydrostatic equilibrium.

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Outline of Jupiter



Great Red Spot

Magnetosphere Rings


Inner moons

Adrastea Amalthea Metis Thebe

Galilean moons

Callisto Europa Ganymede Io

Irregular moons

Ananke group Carme group Himalia group Pasiphae group

Ungrouped moons

Carpo Themisto S/2003 J 2 S/2003 J 12 S/2011 J 1



Jupiter-crossing minor planets Solar eclipses


Greek camp Trojan camp

Impact events

Shoemaker–Levy 9 2009 Jupiter
impact event 2010 Jupiter
impact event

Exploration and orbiting missions




Cassini Galileo New Horizons Pioneer program

Pioneer 10 Pioneer 11

Ulysses Voyager program

Voyager 1 Voyager 2


Icy Moons Explorer (2022) Europa Clipper
Europa Clipper


Io Volcano Observer
Io Volcano Observer
(2021) Laplace-P
(2023) Smara (2030)



Jovian Jupiter Moons


Book Category Portal

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The Solar System

The Sun Mercury Venus Earth Mars Ceres Jupiter Saturn Uranus Neptune Pluto Haumea Makemake Eris


Terrestrial planets

Mercury Venus Earth Mars

Giant planets

Jupiter Saturn Uranus Neptune

Dwarf planets

Ceres Pluto Haumea Makemake Eris


Jovian Saturnian (Rhean) Charikloan Chironean Uranian Neptunian Haumean



Moon other near- Earth


Phobos Deimos


Ganymede Callisto Io Europa all 69


Titan Rhea Iapetus Dione Tethys Enceladus Mimas Hyperion Phoebe all 62


Titania Oberon Umbriel Ariel Miranda all 27


Triton Proteus Nereid all 14


Charon Nix Hydra Kerberos Styx


Hiʻiaka Namaka


S/2015 (136472) 1




Solar System
Solar System

By size By discovery date

Minor planets Gravitationally rounded objects Possible dwarf planets Natural satellites Comets

Small Solar System bodies

Meteoroids Minor planets


Comets Damocloids Mercury-crossers Venus-crossers Venus
trojans Near- Earth
objects Earth-crossers Earth
trojans Mars-crossers Mars
trojans Asteroid
belt Asteroids

first discovered: Ceres Pallas Juno Vesta

Families Notable asteroids Kirkwood gap Main-belt comets Jupiter
trojans Jupiter-crossers Centaurs Saturn-crossers Uranus
trojans Uranus-crossers Neptune
trojans Cis-Neptunian objects Trans-Neptunian objects Neptune-crossers Plutoids Kuiper belt

Plutinos Cubewanos

Scattered disc Detached objects Sednoids Hills cloud Oort cloud

Hypothetical objects

Vulcan Vulcanoids Phaeton Planet
V Theia Fifth giant Planets beyond Neptune Tyche Nemesis Planet

Exploration (outline)


Astronomy Timeline

Spaceflight Robotic spacecraft Human spaceflight List of crewed spacecraft Colonization List of probes Timeline

Mercury Venus Moon Mars Ceres Asteroids


Comets Jupiter Saturn Uranus Neptune Pluto Deep space

Outline of the Solar System Portals Solar System Astronomy Earth
sciences Mars Jupiter Uranus Cosmology

Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way
Milky Way
subgroup → Local Group → Virgo Supercluster → Laniakea Supercluster → Observable universe → Universe Each arrow (→) may be read as "within" or "part of".

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Galileo Galilei

Scientific career

Observational astronomy Galileo affair Galileo's escapement Galilean invariance Galilean moons Galilean transformation Leaning Tower of Pisa experiment Phases of Venus Celatone Thermoscope


The Assayer De Motu Antiquiora Dialogue Concerning the Two Chief World Systems "Discourse on the Tides" "Letter to the Grand Duchess Christina" Sidereus Nuncius Two New Sciences


Vincenzo Galilei
Vincenzo Galilei
(father) Michelagnolo Galilei
Michelagnolo Galilei
(brother) Vincenzo Gamba
Vincenzo Gamba
(son) Maria Celeste
Maria Celeste
(daughter) Marina Gamba
Marina Gamba


"And yet it moves" Villa Il Gioiello Galileo's paradox Sector Museo Galileo

Galileo's telescopes

Tribune of Galileo

In popular culture

Life of Galileo
Life of Galileo
(1943 play) Lamp At Midnight
Lamp At Midnight
(1947 play) Galileo (1968 film) Galileo (1975 film) Starry Messenger (1996 book) Galileo's Daughter: A Historical Memoir of Science, Faith, and Love (1999 book) Galileo Galilei
Galileo Galilei
(2002 opera) Galileo's Dream
Galileo's Dream