Period of rotation (equatorial): 9 hr. 50 min. 30 sec.
Mean orbital velocity: 8.1 miles (13.1 km) per second
Inclination of axis: 3.1 degrees
Orbital eccentricity: 0.048
Orbital inclination: 1.31 degrees
Diameter at equator: 88,800 miles (142,900 km)
11.2 x Earth's diameter
Oblateness: 0.064
Mass: 1.9 x 10^30 kg
318 x Earth╒s mass
Volume: 1.43 x 10^15 km^3
1,323 x Earth's volume
Density: 1.33 g/cm^3
0.239 x Earth's density
Surface gravity: 22.9 m/s^2
2.64 x Earth's gravity
Escape velocity: 37.0 miles (59.5 km) per second
Mean surface temperature:-238 F / -150 C / 123 K (at cloud tops)
Maximum apparent diameter as seen from Earth: 50.1╙
Albedo: 0.44
Number of known satellites: 16
Mean diameter of Sun as seen from the planet: 6' 09"
Satellite data
Metis (J16)
Mean distance from center of Jupiter: 79,530 miles (127,960 km)
Inclination of Axis: 0 degrees
Rotation period: 0.30 days
Orbital period: 0.30 days
Orbital eccentricity: 0
Orbital inclination to Jupiter's equator: 0 degrees
Diameter: 25 miles (40 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.01 mile (0.02 km) per second
Maximum apparent diameter as seen from Jupiter: ---
Adrastea (J15)
Mean distance from center of Jupiter: 80,160 miles (128,980 km)
Inclination of Axis: 0 degrees
Rotation period: 0.29 days
Orbital period: 0.30 days
Orbital eccentricity: 0
Orbital inclination to Jupiter's equator: 0 degrees
Diameter: 16 x 12 x 10 miles (26 x 20 x 16 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.01 miles (0.02 km) per second
Maximum apparent diameter as seen from Jupiter: ---
Amalthea (J5)
Mean distance from center of Jupiter: 112,680 miles (181,500 km)
Inclination of Axis: 0 degrees
Rotation Period: 0.498 days
Orbital period: 0.498 days
Orbital eccentricity: 0.003
Orbital inclination to Jupiter's equator: 0.45 degrees
Diameter: 163 x 91 x 83 miles (262 x 146 x 134 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.01 mile (0.2 km) per second
Maximum apparent diameter as seen from Jupiter: 7' 24"
Thebe (J14)
Mean distance from center of Jupiter: 137,900 miles (221,900 km)
Inclination of axis: 0 degrees
Rotation period: 0.675 days
Orbital period: 0.675 days
Orbital eccentricity: 0.01
Orbital inclination to Jupiter's equator: approx. 0.9 degrees
Diameter: 68 x 62 x 56 miles (110 x 100 x 90 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.03 mile (0.05 km) per second
Maximum apparent diameter as seen from Jupiter: ---
Io (J1)
Mean distance from center of Jupiter: 262,030 miles (421,600 km)
Inclination of axis: 0 degrees
Rotation period: 1.769 days
Orbital period: 1.769 days
Orbital eccentricity: 0.0
Orbital inclination to Jupiter's equator: 0.04 degrees
Diameter: 2,264 miles (3,642 km)
Mass: 8.89 x 10^22 kg
Density: 3.53 g/cm^3
Escape velocity: 1.59 miles (2.56 km) per second
Maximum apparent diameter as seen from Jupiter: 35' 40"
Europa (J2)
Mean distance from center of Jupiter: 416,970 miles (670,900 km)
Inclination of axis: 0 degrees
Rotation period: 3.551 days
Orbital period: 3.551 days
Orbital eccentricity: 0.0
Orbital inclination to Jupiter's equator: 0.47 degrees
Diameter: 1,945 miles (3,130 km)
Mass: 4.79 x 10^22 kg
Density: 3.03 g/cm^3
Escape velocity: 1.27 miles (2.04 km) per second
Maximum apparent diameter as seen from Jupiter: 17' 30"
Ganymede (J3)
Mean distance from center of Jupiter: 665,000 miles (1,070,000 km)
Inclination of axis: 0 degrees
Rotation period: 7.155 days
Orbital period: 7.155 days
Orbital eccentricity: 0.002
Orbital inclination to Jupiter's equator: 0.18 degrees
Diameter: 3,274 miles (5,268 km)
Mass: 1.48 x 10^23 kg
Density: 1.93 g/cm^3
Escape velocity: 1.73 miles (2.78 km) per second
Maximum apparent diameter as seen from Jupiter: 18' 06"
Callisto (J4)
Mean distance from center of Jupiter: 1,168,400 miles (1,884,000 km)
Inclination of axis: 0 degrees
Rotation period: 16.689 days
Orbital period: 16.689 days
Orbital eccentricity: 0.007
Orbital inclination to Jupiter's equator: 0.25 degrees
Diameter: 2,987 miles (4,806 km)
Mass: 1.08 x 10^23 kg
Density: 1.79 g/cm^3
Escape velocity: 1.51 miles (2.43 km) per second
Maximum apparent diameter as seen from Jupiter: 9' 30"
Leda (J13)
Mean distance from center of Jupiter: 6,805,000 miles (11,110,000 km)
Inclination of Axis: unknown
Rotation period: unknown
Orbital period: 238.7 days
Orbital eccentricity: 0.148
Orbital inclination to Jupiter's equator: 26.7 degrees
Diameter: 10 miles (16 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.003 mile (0.005 km) per second
Maximum apparent diameter as seen from Jupiter: 0.2"
Himalia (J6)
Mean distance from center of Jupiter: 7,134,900 miles (11,480,000 km)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 250.6 days
Orbital eccentricity: 0.158
Orbital inclination to Jupiter's equator: 27.6 degrees
Diameter: 106 miles (170 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.06 mile (0.1 km) per second
Maximum apparent diameter as seen from Jupiter: 8.2"
Lysithea (J10)
Mean distance from center of Jupiter: 7,284,000 miles (11,720,000 km)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 259.2 days
Orbital eccentricity: 0.12
Orbital inclination to Jupiter's equator: 29.0 degrees
Diameter: 25 miles (40 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.006 mile (0.01 km) per second
Maximum apparent diameter as seen from Jupiter: 0.1"
Elara (J7)
Mean distance from center of Jupiter: 7,295,000 miles (11,737,000 km)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 259.7 days
Orbital eccentricity: 0.207
Orbital inclination to Jupiter's equator: 24.8 degrees
Diameter: 50 miles (80 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.02 mile (0.03 km) per second
Maximum apparent diameter as seen from Jupiter: 1.4"
Ananke (J12)
Mean distance from center of Jupiter: 12,865,000 miles (20,700,000 km)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 617 days
Orbital eccentricity: 0.17
Orbital inclination to Jupiter's equator: 147 degrees
Diameter: 12 miles (20 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.006 mile (0.01 km) per second
Maximum apparent diameter as seen from Jupiter: approx. 0.02"
Carme (J11)
Mean distance from center of Jupiter: 14,046,000 miles (22,600,000 km)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 692 days
Orbital eccentricity: 0.21
Orbital inclination to Jupiter's equator: 164 degrees
Diameter: 27 miles (44 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.01 mile (0.02 km) per second
Maximum apparent diameter as seen from Jupiter: approx. 0.02"
Pasiphae (J8)
Mean distance from center of Jupiter: 14,480,000 miles (23,300,000 km)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 735 days
Orbital eccentricity: 0.40
Orbital inclination to Jupiter's equator: 147 degrees
Diameter: 22 miles (36 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.01 miles (0.02 km) per second
Maximum apparent diameter as seen from Jupiter: approx. 0.02"
Sinope (J9)
Mean distance from center of Jupiter: 14,730,000 miles (23,700,000 km)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 758 days
Orbital eccentricity: 0.28
Orbital inclination to Jupiter's equator: 153 degrees
Diameter: 12 miles (20 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.006 mile (0.01 km) per second
Maximum apparent diameter as seen from Jupiter: approx. 0.01"
Planet composition
Jupiter is the largest planet in the solar system. It is more than 318 times as massive as the Earth. Jupiter, as well as the other giant planets, has a composition very similar to that of the Sun and the original solar nebula: it is mainly hydrogen and helium with traces of heavier elements. However, Jupiter probably does have a small rocky core of silicate minerals and iron.
Though comparatively small, the core is several times the size of any of the terrestrial planets. Surrounding the core and a thin layer of liquid helium is a thick layer of liquid metallic hydrogen. Hydrogen under pressures such as those in Jupiter will become ionized and act like a metal. Convection in this metallic layer, together with the planet's rotation, creates the extremely strong magnetic field around Jupiter. Surrounding the metallic hydrogen is a layer of molecular hydrogen. The outer shell of the planet consists of a relatively thin layer of hydrogen and helium gas topped with a cloud layer.
Near the transition from gaseous to liquid hydrogen the temperature is thought to be 3,140 F / 1,730 C / 2,000 K and the pressure is about 5,600 atm. At the point where the hydrogen begins having metallic characteristics, the temperature is over 19,340 F / 10,730 C / 11,000 K and the pressure is about 3,000,000 atm. Maximum temperatures and pressures reach 53,540 F / 29,730 C / 30,000 K and 100 million atm at the core.
Rocky Core: radius of 10,000 km
Liquid Helium Layer: 3,000 km thick
Liquid Metallic Hydrogen Layer: 32,000 km thick
Liquid Hydrogen Layer: 24,000 km thick
Hydrogen and Helium Gas Layer: 2,500 km thick
Topography
The most prominent "topographical" feature is the Great Red Spot (16,280 x 8,575 miles). Located in atmosphere over the southern hemisphere, this hurricane-like storm is more than twice the size of Earth. It was perhaps first seen and documented by Robert Hooke in 1664, but researchers believe it may be millions of years old. The Great Red Spot is much colder than its surroundings, with temperatures averaging -202░F. As a high-pressure region, the Great Red Spot spins the opposite direction of low-pressure storms on Jupiter.
Atmosphere
Jupiter's atmosphere is largely hydrogen (90% by volume) and helium (4.5% by volume). Ammonia, methane, ethane, acetylene, water vapor, phosphine, carbon monoxide, and germanium tertrahydride are present in small quantities (each between 0.1 and 0.0000001% by volume). The very top of the atmosphere, however, is dominated by the molecules shown in the chart to the left. It is these layers of molecules that compose the colorful bands of clouds seen on Jupiter.
The basic layers (troposphere, stratosphere, etc.) of Jupiter's atmosphere resemble those of the Earth, though each layer is about twice the thickness of the corresponding layer of the Earth's atmosphere. The uppermost layers of the atmosphere are not well understood. In addition, the definition of the "bottom" of the atmosphere is somewhat arbitrary because there is no surface similar to the Earth's surface.
The atmosphere surrounding Jupiter contains dark streaks (known as cloud belts) and bright bands (known as cloud zones). Several of each variety are relatively stable, changing only slightly in latitude though some occasionally disappear. Ammonia crystals form white clouds in Jupiter's atmosphere, while sulfur compounds (and perhaps phosphorus) produce the brown and orange hues typically associated with Jupiter's appearance. In addition, there are oval structures, probably cyclone-like storms, between some of the belts and zones. The best known of these is the Great Red Spot; the GRS is very stable and has probably existed for over 300 years.
Magnetic fields and gravity
Researchers believe that Jupiter's magnetic field is generated by a dynamo created by conduction in Jupiter's metallic hydrogen layer in conjunction with the planet's rotation. Jupiter's field is inclined to the planet's axis of rotation by an angle of about 11 degrees, and the alignment of the magnetic poles is such that a compass needle would point south.
Jupiter has a magnetic field stronger than that of any other planet. This
produces a magnetosphere whose dimensions are up to 1200 times those of the
Earth's magnetosphere. If the magnetosphere were visible to the naked eye,
from the Earth it would appear larger than the Sun in the sky. The bow shock
is located in the direction of the Sun at a distance of 50 to 100 Jupiter
radii from the planet. The magneto tail extends at least 650 million km
behind the planet--out to Saturn's orbit and even further.
The pressure exerted by the solar wind on the magnetosphere is much smaller
than the pressure on planets closer to the Sun; this, together with Jupiter's
strong magnetic field, is the reason the magnetosphere is so large. The
magnetic axis is tilted 9.5 deg to the rotational axis. It is Jupiter's
rotation and liquid metallic hydrogen interior which power the magnetic field.
Like the Earth, Jupiter has large belts of charged particles trapped by its
magnetic field. These belts extend out to twenty Jupiter radii. The particles
have ten times the energy and are a million times denser than those in the
Earth's Van Allen belts.
Jupiter's surface gravity is 2.69 times the Earth's.
Orbit and rotation
Jupiter has an elliptical orbit that takes 4,332.59 days (11.86 years) to complete. Because it is mostly fluid, Jupiter's period of rotation varies with latitude, the fastest rotation being at the equator (9 hours 50 minutes 30 seconds). This fast rotation causes a bulge to form, making the planet's equatorial diameter about 142,800 km, while its polar diameter is only 132,400 km.
Moons (and/or rings)
Jupiter has 16 known satellites. The four largest: Io, Europa, Ganymede, and Callisto are known collectively as the Galileans in honor of the first observer, Galileao Galilei on 7 January 1610. All the Galileans have a synchronous rotation (they orbit Jupiter in the same amount of time it takes to rotate on their axes) and all are the size of planets. Of note, Io has nine active volcanoes, the only such volcanoes known in the solar system (except on Earth).
Jupiter is also surrounded by rings, which consist of several segments and seem to extend to the planet's surface. Researchers believe that the are made up of relatively high-density rocks (dust), as opposed to the icy material found in Saturn's rings. They also believe the rings originated from the gravitational break-up of a tiny inner satellites, plus materials from other satellites, comets, and meteorites.
Mythology
Jupiter was named for the ruler of Olympus. Amalthea was named for the one who suckled Zeus (Greek for Jupiter) as a young child. Io was named for the daughter of Inachus. Europa was named for the beautiful daughter of Agenor, king of Tyhre. Ganymede was named for a beautiful young boy who, after being carried to Olympus by Zeus, became cup bearer of the Olympian gods. Callisto was named for the beautiful daughter of Lycaon.
Discovery and exploration
In 1972, NASA sent the first of four spacecraft slated to conduct the initial surveys. Pioneer 10 lifted off in March 1972 and returned the first close-up images of Jupiter in December 1973, flying within 132,252 km (82,178 miles) of the cloud tops. Pioneer 11 followed 1 year later. Voyagers 1 and 2 were launched in the summer of 1977 and did flybys in 1979.
A new mission to Jupiter, known as the Galileo project, is under way. On December 7, 1995, the orbiter will spend two years circling the planet and flying close to the large moons. It will also drop an atmospheric probe into the cloud layers to relay information back to Earth.
