Jupiter

Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, and slightly less than one one-thousandth the mass of the Sun. Jupiter orbits the Sun at a distance of 5.20 AU (778.5 Gm) with an orbital period of 11.86 years. Jupiter is the third brightest natural object in the Earth's night sky after the Moon and Venus, and it has been observed since prehistoric times. It was named after Jupiter, the chief deity of ancient Roman religion.

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Jupiter

Full disk view of Jupiter in natural color, with the shadow of its largest moon Ganymede cast onto it and the Great Red Spot at the left horizon.
Designations
Pronunciation	/ˈdʒuːpɪtər/ ⓘ[1]
Named after	Jupiter
Adjectives	Jovian /ˈdʒoʊviən/
Symbol
Orbital characteristics[2]
Epoch J2000
Aphelion	816.363 Gm (5.4570 AU)
Perihelion	740.595 Gm (4.9506 AU)
Semi-major axis	778.479 Gm (5.2038 AU)
Eccentricity	0.0489
Orbital period (sidereal)	11.862 yr 4,332.59 d 10,476.8 Jovian solar days[3]
Orbital period (synodic)	398.88 d
Average orbital speed	13.07 km/s (8.12 mi/s)
Mean anomaly	20.020°[4]
Inclination	1.303° to ecliptic[4] 6.09° to Sun's equator[4] 0.32° to invariable plane[5]
Longitude of ascending node	100.464°
Time of perihelion	21 January 2023[6]
Argument of perihelion	273.867°[4]
Known satellites	95 (as of 2023[update])[7]
Physical characteristics[2][8][9]
Mean radius	69,911 km (43,441 mi)[lower-alpha 1] 10.973 of Earth's
Equatorial radius	71,492 km (44,423 mi)[lower-alpha 1] 11.209 R🜨 (of Earth's) 0.10045 R☉ (of Sun's)
Polar radius	66,854 km (41,541 mi)[lower-alpha 1] 10.517 of Earth's
Flattening	0.06487
Surface area	6.1469×1010 km2 (2.3733×1010 sq mi) 120.4 of Earth's
Volume	1.4313×1015 km3 (3.434×1014 cu mi)[lower-alpha 1] 1,321 of Earth's
Mass	1.8982×1027 kg (4.1848×1027 lb) 317.8 of Earth's 1/1047 of Sun's[10]
Mean density	1,326 kg/m3 (2,235 lb/cu yd)[lower-alpha 2]
Surface gravity	24.79 m/s2 (81.3 ft/s2)[lower-alpha 1] 2.528 g
Moment of inertia factor	0.2756±0.0006[11]
Escape velocity	59.5 km/s (37.0 mi/s)[lower-alpha 1]
Synodic rotation period	9.9258 h (9 h 55 m 33 s)[3]
Sidereal rotation period	9.9250 hours (9 h 55 m 30 s)
Equatorial rotation velocity	12.6 km/s (7.8 mi/s; 45,000 km/h)
Axial tilt	3.13° (to orbit)
North pole right ascension	268.057°; 17h 52m 14s
North pole declination	64.495°
Albedo	0.503 (Bond)[12] 0.538 (geometric)[13]
Temperature	88 K (−185 °C) (blackbody temperature)
Surface temp. min mean max 1 bar 165 K 0.1 bar 78 K 128 K
Apparent magnitude	−2.94[14] to −1.66[14]
Absolute magnitude (H)	−9.4[15]
Angular diameter	29.8" to 50.1"
Atmosphere[2]
Surface pressure	200–600 kPa (30–90 psi) (opaque cloud deck)[16]
Scale height	27 km (17 mi)
Composition by volume	89%±2.0% hydrogen 10%±2.0% helium 0.3%±0.1% methane 0.026%±0.004% ammonia 0.0028%±0.001% hydrogen deuteride 0.0006%±0.0002% ethane 0.0004%±0.0004% water

Jupiter was the first planet to form, and its inward migration during the primordial Solar System impacted much of the formation history of the other planets. Jupiter is primarily composed of hydrogen (90% by volume), followed by helium, which makes up a quarter of its mass and a tenth of its volume. The ongoing contraction of Jupiter's interior generates more heat than the planet receives from the Sun. Its internal structure is believed to comprise an outer mantle of liquid metallic hydrogen, and a diffuse inner core of denser material. Because of its rapid rotation rate of 1 rotation per 10 hours, Jupiter's shape is an oblate spheroid: it has a slight but noticeable bulge around the equator. The outer atmosphere is divided into a series of latitudinal bands, with turbulence and storms along their interacting boundaries. The most obvious result of this is the Great Red Spot, a giant storm which has been observed since 1831 and possibly earlier.

Jupiter is surrounded by a faint planetary ring system and has a powerful magnetosphere, the second largest contiguous structure in the Solar System (after the heliosphere). Jupiter forms a system of 95 known moons and probably many more, including the four large moons discovered by Galileo Galilei in 1610: Io, Europa, Ganymede, and Callisto. Ganymede, the largest of the four, is larger than the planet Mercury. Callisto is the second largest; Io and Europa are approximately the size of Earth's Moon.

Since 1973, Jupiter has been visited by nine robotic probes: seven flybys and two dedicated orbiters, with two more either en route or awaiting launch.