Jovian Facts

Jupiter

This giant planet spins faster than any other. At the equator, the velocity due to spinning motion is about 28,400 mph (45,500 km/h). The equivalent velocity on Earth is about 320 mph (420 km/h). Jupiter bulgest at its equator because it is not solid, and is spinning so fast.

Jupiter has no definite surface but, under the outer cloud layers, the gas thickens as the pressure gets greater, gradually becoming like a hot liquid. The atmosphere is stormy, with high winds and lightning, which is probably quite violent.

Three faint ring of fine particles circle Jupiter. They are only a few miles thick and cannot be seen from Earth even with the most powerful telescopes. They were first discovered on images returned by the spacecraft Voyager 1. The rings form a band about 31,000 miles (50,000 km) above Jupiter's cloud tops.

At its center, Jupiter almost certainly has a small rocky core. The temperature there is around 36,000 - 54,000�F.

In the layer over the core, the very high pressure makes the liquid hydrogen behave like a molten metal.

Jupiter is mainly made of hydrogen (88%) and helium (11%). Small amounts of other checmicals give the clouds their variety of colors.

Jupiter's Great Red Spot is thought to be a swirling storm cloud currently about 16,000 miles (26,000 km) long and 7,500 miles (12,000 km) wide. Since it was first observed in 1664, its length and color have varied. Why it is red is still a mystery. Small white clouds that get caught up around the swirling Red Spot take about 7 days to go right around it and then they merge in with the cloud bands.

Four of Jupiter's moons were discovered in 1610 by the Italian astronomer Galileo, when he first used a telescope; so they are known as the Galilean satellites. None is more than a tiny spot of light when viewed with even the most powerful telescopes. Images sent back by the Voyager spacecraft showed just how different they are from each other.

Jovian Facts

Mass (kg)	1.90 x 10^27
Diameter (km)	142,800
Mean Density (kg/m^3)	1,314
Escape Velocity (m/sec)	59,500
Average Distance from Sun (AU)	5.203
Rotation Period (length of day in Earth hours)	9.8
Revolution Period (length of year in Earth years)	11.86
Obliquity (tilt of axis)	3.08�
Orbit Inclination	1.3�
Orbit Eccentricity (deviation from circular)	0.048
Mean Surface Temperature	120�K (cloud tops)
Visual Geometric Albedo (Reflectivity)	0.44
Atmospheric Components	90% Hydrogen, 10% Helium, .07% Methane
Rings	Faint ring. Infrared spectra imply dark rock fragments.

Probes that have gone to Jupiter

1973	Pioneer 10 (USA)	First flyby of Jupiter
1974	Pioneer 11 (USA)	Flyby
March 1974	Voyager 1 (USA)	Close flyby returning detailed images of planet and five moons
July 1979	Voyager 2 (USA)	Similar mission to Voyager 1

The Galilean Moons of Jupiter

Name	Radius km (mi)	Orbital Radius 10^3km (10^3mi)	Orbital Period (days)
Io	1815 (1128)	421.6 (262.0)	1.769
Europa	1569 (975)	670.9 (416.9)	3.551
Ganymede	2631 (1635)	1070 (665)	7.155
Callisto	2400 (1491)	1880 (1168)	16.689

Other Jovian Satellites

Name	Radius km (mi)	Orbital Radius 10^3km (10^3mi)	Orbital Period (days)
Metis	20 (12)	127.96 (79.51)	0.295
Adrastea	12,10,8 (7,6,5)	128.98 (80.14)	0.298
Amalthea	75,85,135 (47,53,85)	181.3 (112.7)	0.498
Thebe	45-55 (28-34)	221.9 (137.9)	0.675
Leda	5(3)	11,094 (6,893)	238.7
Himalia	90(55)	11,480 (7,133)	250.6
Lysithea	10(6)	11,720 (7,282)	259.2
Elara	40(25)	11,737 (7,293)	259.7
Ananke	10(6)	21,200 (13,200)	631
Carme	15(9)	22,600 (14,000)	692
Pasiphae	20(12)	23,500 (14,600)	735
Sinope	15(9)	23,700 (14,700)	758

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