JUPITER

This article is about the planet. For other uses, see Jupiter (disambiguation).

Jupiter

A composite Cassini image of Jupiter. The dark spot is the shadow of Europa. The Great Red Spot, a persistent anticyclonic storm, is at lower right. White atmospheric bands, termed zones, represent areas of upwelling; brown bands, called belts, represent areas of downwelling. They display high-altitude ammonia ice clouds and lower clouds of unknown composition, respectively.
Designations
Pronunciation	i/ˈdʒuːpɨtər/[1]
Adjective	Jovian
Orbital characteristics[5][a]
Epoch J2000
Aphelion	816,520,800 km (5.458104 AU)
Perihelion	740,573,600 km (4.950429 AU)
Semi-major axis	778,547,200 km (5.204267 AU)
Eccentricity	0.048775
Orbital period	4,332.59 days 11.8618 yr 10,475.8 Jupiter solar days[2]
Synodic period	398.88 days[3]
Average orbital speed	13.07 km/s[3]
Mean anomaly	18.818°
Inclination	1.305° to Ecliptic 6.09° to Sun's equator 0.32° to Invariable plane[4]
Longitude of ascending node	100.492°
Argument of perihelion	275.066°
Satellites	67[3]
Physical characteristics
Mean radius	69,911 ± 6 km[6][b]
Equatorial radius	71,492 ± 4 km[6][b] 11.209 Earths
Polar radius	66,854 ± 10 km[6][b] 10.517 Earths
Flattening	0.06487 ± 0.00015
Surface area	6.1419×1010 km2[b][7] 121.9 Earths
Volume	1.4313×1015 km3[3][b] 1321.3 Earths
Mass	1.8986×1027 kg[3] 317.8 Earths 1/1047 Sun[8]
Mean density	1.326 g/cm3[3][b]
Equatorial surface gravity	24.79 m/s2[3][b] 2.528 g
Escape velocity	59.5 km/s[3][b]
Sidereal rotation period	9.925 h[9] (9 h 55 m 30 s)
Equatorial rotation velocity	12.6 km/s 45,300 km/h
Axial tilt	3.13°[3]
North pole right ascension	268.057° 17 h 52 min 14 s[6]
North pole declination	64.496°[6]
Albedo	0.343 (Bond) 0.52 (geom.)[3]
Surface temp. min mean max 1 bar level 165 K[3] 0.1 bar 112 K[3]
Apparent magnitude	-1.6 to -2.94[3]
Angular diameter	29.8" – 50.1"[3]
Atmosphere[3]
Surface pressure	20–200 kPa[10] (cloud layer)
Scale height	27 km
Composition	89.8±2.0% hydrogen (H2) 10.2±2.0% helium (He) ~0.3% methane (CH4) ~0.026% ammonia (NH3) ~0.003% hydrogen deuteride (HD) 0.0006% ethane (C2H6) 0.0004% water (H2O) Ices: ammonia (NH3) water (H2O) ammonium hydrosulfide (NH4SH)

Jupiter is the fifth planet from the Sun and the largest planet in the Solar System.^[11] It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in the Solar System combined. Jupiter is classified as a gas giant along with Saturn, Uranus and Neptune. Together, these four planets are sometimes referred to as the Jovian or outer planets. The planet was known by astronomers of ancient times,^[12] and was associated with the mythology and religious beliefs of many cultures. The Romans named the planet after the Roman god Jupiter.^[13] When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, bright enough to cast shadows,^[14] and making it on average the third-brightest object in the night sky after the Moon and Venus. (Mars can briefly match Jupiter's brightness at certain points in its orbit.)
Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, although helium only comprises about a tenth of the number of molecules. It may also have a rocky core of heavier elements,^[15] but like the other gas giants, Jupiter lacks a well-defined solid surface. Because of its rapid rotation, the planet's shape is that of an oblate spheroid (it possesses a slight but noticeable bulge around the equator). The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope. Surrounding Jupiter is a faint planetary ring system and a powerful magnetosphere. There are also at least 67 moons, including the four large moons called the Galilean moons that were first discovered by Galileo Galilei in 1610. Ganymede, the largest of these moons, has a diameter greater than that of the planet Mercury.
Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early Pioneer and Voyager flyby missions and later by the Galileo orbiter. The most recent probe to visit Jupiter was the Pluto-bound New Horizons spacecraft in late February 2007. The probe used the gravity from Jupiter to increase its speed. Future targets for exploration in the Jovian system include the possible ice-covered liquid ocean on the moon Europa.