Jupiter is one of the four gas giants; that is, it is not primarily composed of solid matter. It is the largest planet in the Solar System, having a diameter of 142,984 km at its equator. Jupiter's density, 1.326 g/cm³, is the second highest of the gas giant planets, but lower than any of the four terrestrial planets.
Jupiter's upper atmosphere is composed of about 88–92% hydrogen and 8–12% helium by percent volume or fraction of gas molecules (see table to the right). Since a helium atom has about four times as much mass as a hydrogen atom, the composition changes when described in terms of the proportion of mass contributed by different atoms. Thus the atmosphere is approximately 75% hydrogen and 24% helium by mass, with the remaining one percent of the mass consisting of other elements. The interior contains denser materials such that the distribution is roughly 71% hydrogen, 24% helium and five percent other elements by mass. The atmosphere contains trace amounts of methane, water vapor, ammonia, and silicon-based compounds. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, and sulfur. The outermost layer of the atmosphere contains crystals of frozen ammonia] Through infrared and ultraviolet measurements, trace amounts of benzene and other hydrocarbons have also been found.
The atmospheric proportions of hydrogen and helium are very close to the theoretical composition of the primordial solar nebula. However, neon in the upper atmosphere only consists of 20 parts per million by mass, which is about a tenth as abundant as in the Sun. Helium is also depleted, although only to about 80% of the Sun's helium composition. This depletion may be a result of precipitation of these elements into the interior of the planet.Abundances of heavier inert gases in Jupiter's atmosphere are about two to three times that of the sun.
Designations
Pronunciation
/ˈdʒuːpɨtər/
Adjective Jovian
Orbital characteristics
Epoch J2000:
Aphelion816,520,800 km (5.458104 AU)
Perihelion740,573,600 km (4.950429 AU)
Semi-major axis778,547,200 km (5.204267 AU)
Eccentricity0.048775
Orbital period4,331.572 days11.85920 yr
Synodic period398.88 days
Average orbital speed13.07 km/s
Mean anomaly18.818°
Inclination1.305° to Ecliptic6.09° to Sun's equator0.32° to Invariable planet
Longitude of ascending node100.492°
Argument of perihelion275.066°
Satellites63
Physical characteristics
Equatorial radius71,492 ± 4 km,11.209 Earths
Polar radius66,854 ± 10 km,10.517 Earths
Flattening0.06487 ± 0.00015
Surface area6.21796×1010 ,km²121.9 Earths
Volume1.43128×1015 km³1321.3 Earths
Mass1.8986×1027 kg317.8 EarthsMean
density1.326 g/cm³
Equatorial surface gravity
24.79 m/s² 2.528 g
Escape velocity
59.5 km/s
Sidereal rotationperiod
9.925 h
Equatorial rotation velocity12.6 km/s45,300 km/h
Axial tilt3.13°
North pole right ascension
268.057°17 h 52 min 14 s
North pole declination
64.496°
Albedo0.34 (bond)0.52
(geom.)
Surface temp. 1 bar level 0.1
min mean max
165k
112k
Apparent magnitude
-1.6 to -2.94
Angular diameter
29.8" — 50.1"
Cloud layers :
Jupiter is perpetually covered with clouds composed of ammonia crystals and possibly ammonium hydrosulfide. The clouds are located in the tropopause and are arranged into bands of different latitudes, known as tropical regions. These are sub-divided into lighter-hued zones and darker belts. The interactions of these conflicting circulation patterns cause storms and turbulence. Wind speeds of 100 m/s (360 km/h) are common in zonal jets.The zones have been observed to vary in width, color and intensity from year to year, but they have remained sufficiently stable for astronomers to give them identifying designations.
The cloud layer is only about 50 km deep, and consists of at least two decks of clouds: a thick lower deck and a thin clearer region. There may also be a thin layer of water clouds underlying the ammonia layer, as evidenced by flashes of lightning detected in the atmosphere of Jupiter. (Water is a polar molecule that can carry a charge, so it is capable of creating the charge separation needed to produce lightning.) These electrical discharges can be up to a thousand times as powerful as lightning on the Earth. The water clouds can form thunderstorms driven by the heat rising from the interior.
The orange and brown coloration in the clouds of Jupiter are caused by upwelling compounds that change color when they are exposed to ultraviolet light from the Sun. The exact makeup remains uncertain, but the substances are believed to be phosphorus, sulfur or possibly hydrocarbons. These colorful compounds, known as chromophores, mix with the warmer, lower deck of clouds. The zones are formed when rising convection cells form crystallizing ammonia that masks out these lower clouds from view.
Jupiter's low axial tilt means that the poles constantly receive less solar radiation than at the planet's equatorial region. Convection within the interior of the planet transports more energy to the poles, however, balancing out the temperatures at the cloud layer.
