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Moons of Jupiter

Since the discovery of Jupiter's four largest moons (satellites) in 1610 by Galileo Galilee, the number of discovered moons orbiting Jupiter has continued to increase. When an astronomer discovers a new moon orbiting Jupiter, it is reported to the International Astronomical Union, which gives it a temporary name until its orbit is confirmed. Once confirmed, the moon is given an appropriate name and added to the list of officially recognized moons. There are currently 50 of such officially named moons (satellites) with another 17 "temporary" moons (satellites) awaiting orbit confirmation.

An illustration of Jupiter's 4 Galilean moons.
An illustration of the 4 Galilean moons.

Jupiter's four largest moons are Io, Europa, Ganymede and Callisto. Their discovery provided the crucial evidence that planets in the Solar System orbit the Sun rather than the Earth. It was also the first time that a moon was discovered orbiting a planet other than the Earth.

Io is the third largest of Jupiter's moons and fifth in distance from the planet. It is only slightly larger (diameter 3,643.2 km) than the Earth's moon (3,474 km). It is characterized by the tremendous amount of volcanic activity on its surface. Io is the most volcanically active object in the Solar System. Its surface is covered by a layer of sulfur and more than a dozen volcanoes release hot silicate magma. Io orbits Jupiter once every 42.46 hours (1.76 Earth days).

Europa is the smallest of the four Galilean moons and is sixth in orbit from the planet. Its diameter of 3,121.6 km is slightly smaller than the Earth's moon. Europa's unique feature is its surface of water ice. There is also evidence to suggest that this icy surface may be covering an ocean of either water or slush beneath it. Europa's watery condition is important information because it could possibly support some life forms. Europa orbits Jupiter once every 3.55 days.

Ganymede is the largest of the four Galilean moons and is seventh in orbit from the planet. Ganymede also holds the distinction of being the largest moon in the Solar System, even larger than the planet Mercury. It is the only moon with its own internally generated magnetic field. Its surface is made of silicate rock and water ice and is characterized by dark regions of craters and light regions of grooves and ridges. Ganymede completes one orbit around Jupiter in 7.15 days.

Callisto is the farthest of the Galilean moons. It is roughly the size of Mercury (4,820.6 km vs. 4,879.4 km) but is only one third of the planet's mass. Callisto's ancient and heavily crated surface is a mixture of unknown rocky material and water ice in approximately equal parts. Callisto completes one orbit around Jupiter in 16.68 days.

List of Jupiter's 67 Moons

Name Distance from Jupiter (km) Days for 1 full Orbit around Jupiter Diameter (km) Year Discovered Group
Metis128,1000.3441979Amalthea
Adrastea128,9000.3161979Amalthea
Amalthea181,4000.51681892Amalthea
Thebe221,9000.7981979Amalthea
Io421,8001.83,6431610Galilean
Europa671,1003.63,1221610Galilean
Ganymede1,070,4007.25,2621610Galilean
Callisto1,882,70016.74,8211610Galilean
Themisto7,507,000130.092000Themisto
Leda11,165,000240.9181974Himalia
Himalia11,461,000250.61601904Himalia
Lysithea11,717,000259.2381938Himalia
Elara11,741,000259.6781905Himalia
S/2000 J1112,555,000287.042000Himalia
Carpo16,989,000456.132003Carpo
Euporie19,302,000550.722001Ananke
Orthosie20,721,000622.622001Ananke
Euanthe20,799,000620.632001Ananke
Thyone20,940,000627.342001Ananke
Mneme21,069,000620.022003Ananke
Harpalyke21,105,000623.342000Ananke
Hermippe21,131,000633.942001Ananke
Praxidike21,147,000625.372000Ananke
Thelxinoe21,162,000628.122003Ananke
Iocaste21,269,000631.552000Ananke
Ananke21,276,000610.5281951Ananke
Arche22,931,000723.932002Carme
Pasithee23,096,000719.522001Carme
Herse23,097,000715.422003Carme
Chaldene23,179,000723.842000Carme
Kale23,217,000729.522001Carme
Isonoe23,217,000725.542000Carme
Aitne23,231,000730.232001Carme
Erinome23,279,000728.332000Carme
Taygete23,360,000732.252000Carme
Carme23,404,000702.3461938Carme
Kalyke23,583,000743.052000Carme
Eukelade23,661,000746.442003Carme
Kallichor24,043,000764.722003Carme
Helike21,263,000634.842003Pasiphae
Eurydome22,865,000717.332001Pasiphae
Autonoe23,039,000762.742001Pasiphae
Sponde23,487,000748.322001Pasiphae
Pasiphae23,624,000708.0581908Pasiphae
Megaclite23,806,000752.862000Pasiphae
Sinope23,939,000724.5381914Pasiphae
Hegemone23,947,000739.632003Pasiphae
Aoede23,981,000761.542003Pasiphae
Callirrho24,102,000758.871999Pasiphae
Cyllene24,349,000737.822003Pasiphae
Kore24,543,000779.222003Pasiphae
S/2003 J228,570,410982.522003No Group
S/2003 J318,339,885504.022003No Group
S/2003 J423,257,920723.222003No Group
S/2003 J524,084,180759.742003No Group
S/2003 J922,441,680683.012003No Group
S/2003 J1024,249,600767.022003No Group
S/2003 J1219,002,480533.312003No Group
S/2003 J1522,000,000668.422003No Group
S/2003 J1621,000,000595.422003No Group
S/2003 J1820,700,000606.322003No Group
S/2003 J1922,800,000701.322003No Group
S/2003 J2324,055,500759.722003No Group
S/2010 J123,314,335723.222010No Group
S/2010 J220,307,150588.112010No Group
S/2011 J120,155,290580.712011No Group
S/2011 J223,329,710726.812011No Group