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Jupiter

Distance from sun 778.33 million km, 5.2028 a.u.
Diameter 142,984 km, 11.23 times earth's diameter
Mass 317.938 times earth's mass
Density 1.33
Gravity 2.4 times earth's gravity, escape velocity 59.6 km/s
Rotation 9.841 hours
Orbit Eccentricity 0.0483
Orbit Inclination 1.308 degrees
Axis Tilt 3.12 degrees
Sidereal Period 11.8623 Earth years
Synodic Period 398.99 Earth days

History: Jupiter, called Zeus by the Greeks, was king of the gods. It's consistent brightness and uniform motion throught the sky are propably factors in why they named the planet after their chief god.

Description: Jupiter is by far the largest of the planets and rotates the fastest, doing so in about ten hours. This rotation period is for the equator, different latitudes rotate at different speeds. Jupiter's atmosphere is almost totally made up of hydrogen and helium. The colors of the atmosphere that can be seen from earth are caused by small amounts of trace substances such as methane and ammonia, which change colors at different temperatures. The planet has red, brown, yellow, and occasionally blue tones in different bands. The Great Red Spot, one of the most prominent marks in Jupiter's atmosphere, is actually a storm larger than the size of earth and has been raging for about 300 years. The planet is believed to have a rocky core, but this cannot be proven because of the thick atmosphere. In 1979, the Voyager 1 spacecraft discovered that Jupiter actually has a small ring, too faint to be seen from earth.

Observation: Jupiter's synodic period is about 13 months. Of this, it is visible in the morning for about 5 months and in the evening for about 5 months. At its brightest, it is the fourth brightest object in the sky, at magnitude -2.5, and at close oppositions it reaches an angular size of 50 minutes. The disk of Jupiter as well as the four Galilean satellites can easily be seen in binoculars or a small telescope. A medium size telescope will reveal bands in the atmosphere, the Great Red Spot, and other atmospheric features. The entire planet's surface can be viewed in one night because of its short synodic period. The Galilean satellites vary in revolution from 2 to 17 days, so they appear at a different position each night.

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