Space · Planets

Jupiter

The largest planet — more massive than the other seven combined — a banded gas giant with a centuries-old storm bigger than Earth.

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Quick facts

Type

Gas giant

Distance from Sun

5.203 AU
778.6 million km

Diameter

142,984 km

Mass

317.8 Earth masses
1.898 × 10²⁷ kg

Surface gravity

24.79 m/s²

Day length

9.93 Earth hours

Year length

4331 Earth days
11.86 Earth years

Mean surface temperature

−108 (cloud-top) °C

Atmosphere

89% H₂, 10% He, 0.3% CH₄

Confirmed moons

Naming origin

Roman king of the gods

What's there

Jupiter is the king of the solar system in every dimension that scales. Its mass is 2.5 times that of all other planets put together. Its bands of cream and rust visible through a small telescope are alternating zones (rising air, cooler, cream-colored ammonia) and belts (sinking air, warmer, brown sulfur compounds), driven by Jupiter's rapid 9.9-hour rotation. The Great Red Spot — a 350-year-old anticyclonic storm — is roughly Earth-sized today, having shrunk from twice that in the 19th century; the cause of the shrinkage is unsettled.

Beneath the visible cloud tops, hydrogen transitions from gas to liquid to metallic under enormous pressure; the metallic hydrogen layer is what generates Jupiter's massive magnetic field (the strongest of any planet, 14 times Earth's at the cloud tops). Jupiter has no solid surface to land on. The Galileo orbiter (1995–2003) and Juno orbiter (2016–present) have mapped the interior structure, the magnetic field, and the polar storm systems — Juno revealed unexpected octagonal arrangements of cyclones at the north and south poles.

Who's been there

Mission	Encounter	Year	Status	Primary objective
Pioneer 10 NASA	Flyby	1973	Completed	First Jupiter flyby; confirmed radiation belts.
Pioneer 11 NASA	Flyby	1974	Completed	Second Jupiter flyby; continued to Saturn.
Voyager 1 NASA	Flyby	1979	Completed	Detailed images of Jupiter and its Galilean moons; discovered Io's active volcanism.
Voyager 2 NASA	Flyby	1979	Completed	Jupiter flyby; continued on the Grand Tour to Saturn, Uranus, Neptune.
Ulysses NASA/ESA	Flyby	1992	Completed	Jupiter gravity assist to a solar polar orbit.
Galileo NASA	Orbiter	1995	Completed	First Jupiter orbiter; atmospheric entry probe; comprehensive Galilean-moon mapping. Plunged into Jupiter 2003.
Cassini-Huygens NASA/ESA/ASI	Flyby	2000	Completed	Jupiter flyby en route to Saturn.
New Horizons NASA	Flyby	2007	Completed	Jupiter flyby gravity assist en route to Pluto.
Juno NASA	Orbiter	2016	Active	Polar-orbiting probe; interior structure, magnetic field, atmospheric dynamics.

On the way

Europa Clipper (NASA)

Detailed Europa reconnaissance via ~50 close flybys from Jovian orbit. — arrival ~2030.
JUICE (ESA)

Jupiter Icy Moons Explorer; will ultimately orbit Ganymede in 2034. — arrival ~2031.

Moons

Name	Diameter	Orbital radius	Discovered	Discoverer
Metis	43 km	128,000 km	1979	Stephen P. Synnott (Voyager 2)
Adrastea	16 km	129,000 km	1979	David C. Jewitt (Voyager 2)
Amalthea	167 km	181,400 km	1892	Edward Emerson Barnard
Thebe	98 km	221,900 km	1979	Stephen P. Synnott (Voyager 1)
Io	3643 km	421,800 km	1610	Galileo Galilei
Europa	3122 km	671,100 km	1610	Galileo Galilei
Ganymede	5268 km	1,070,400 km	1610	Galileo Galilei
Callisto	4821 km	1,882,700 km	1610	Galileo Galilei
Themisto	8 km	7,507,000 km	1975, 2000	Charles Kowal & Elizabeth Roemer (1975); rediscovered 2000
Leda	22 km	11,165,000 km	1974	Charles T. Kowal
Himalia	139 km	11,460,000 km	1904	Charles Dillon Perrine
Lysithea	36 km	11,717,000 km	1938	Seth Barnes Nicholson
Elara	79 km	11,740,000 km	1905	Charles Dillon Perrine
Harpalyke	4 km	21,105,000 km	2000	Scott S. Sheppard et al.
Praxidike	7 km	21,148,000 km	2000	Scott S. Sheppard et al.
Iocaste	5 km	21,269,000 km	2000	Scott S. Sheppard et al.
Ananke	28 km	21,276,000 km	1951	Seth Barnes Nicholson
Erinome	3.2 km	23,196,000 km	2000	Scott S. Sheppard et al.
Taygete	5 km	23,360,000 km	2000	Scott S. Sheppard et al.
Carme	47 km	23,404,000 km	1938	Seth Barnes Nicholson
Kalyke	5 km	23,583,000 km	2000	Scott S. Sheppard et al.
Pasiphae	60 km	23,624,000 km	1908	Philibert Jacques Melotte
Megaclite	5 km	23,806,000 km	2000	Scott S. Sheppard et al.
Sinope	38 km	23,939,000 km	1914	Seth Barnes Nicholson
Callirrhoe	9 km	24,102,000 km	1999	James Scotti et al.

This table lists the top 25 moons of Jupiter by size. The full catalog (Jupiter ~95, Saturn ~146, Uranus 28) extends further but the smaller bodies are dim outer irregulars with little encyclopedic content.

Naming etymology

Jupiter takes its name from the Roman king of the gods — the largest, brightest planet visible to the unaided eye after Venus deserved the most senior divine name. The Greeks called the same body Zeus. Babylonian astronomers identified Jupiter with Marduk, the head of their pantheon. The pattern is consistent: cultures gave the dominant planet the dominant god's name. Jupiter's four largest moons (the Galileans — Io, Europa, Ganymede, Callisto) are named for lovers of Zeus from Greek mythology, in keeping with the planet's regal namesake.

Methodology & sources

Numerical data drawn from the NASA Planetary Fact Sheets; satellite parameters from JPL Solar System Dynamics — Physical Parameters and the JPL Satellite Discovery Circumstances table. Mission history cross-referenced against NASA's mission catalog and individual mission pages. Naming etymology from the IAU Working Group for Planetary System Nomenclature. Hero rendering is a stylized SVG composed from primary-source visual reference (NASA / JPL imagery) — no photographs are reproduced.