JUPITER
Jupiter is the fifth planet from the Sun, and the largest.
Facts about Jupiter:
Mass (kg): 1898.6x1024
Equatorial Radius (km): 71492.0
Mean Density (kg/m3): 1326
Length of Day (hours): 9.926
Period of Revolution about Sun (days): 4332.6
Acceleration due to Gravity (m/s2): 23.12
Mean Orbital Velocity (km/s): 13.07
Inclination of Axis (degrees): 3.13
Mean Distance from the Sun (AU): 5.2000
Jupiter's atmosphere: The very top of Jupiter is where the clouds swirl, orbiting in 9 hours 55 minutes with a thickness of 1000 km. This part really is gas with clouds of helium, water vapor, ammonia and hydrogen sulphite, which encompass the globe and erupt in huge lightning storms that dwarf the ones we have. The cloud layer is cut into many bands that track across the surface in opposite directions, and these bands are powered by small eddy currents between them, which in turn are powered by the Sun. The same effect occurs on Earth in many places, but the easiest example to see is a river. The River Severn in Gloucestershire is a prime example: where it becomes wide and slow moving, often one section will flow faster then the other, with spiraling currents between them. And of course there is the Great Red Spot, a huge turbulent storm that feeds off smaller eddy currents. This storm, three times as large as the Earth, has been around since at least 1666, and will be a prominent feature of Jupiter for a long time to come.
Other stuff:
The Rings:
Jupiter has a relatively simple ring system, in three parts. Closest to the planet is the Inner Halo, which is made of fine dust particles. Then comes the Main Ring, which is the brightest. Outside this are the two Gossamer Rings, named Amalthea and Thebe after two small satellites in the ring system. Jupiter's rings were a completely unexpected discovery; two scientists working on the Voyager 1 mission suggested that Voyager should look and see if there were any, as it had traveled so far. The other members of the team thought that the chances of Jupiter having a ring system were practically nil, so it was a big surprise when they turned on the camera and saw them! Jupiter's rings are dynamic. They are formed from micrometeor impacts with Jupiter's inner moons, from which the particles eventually fall towards the planet. Jupiter's rings have been studied extensively by the Earth-based Galileo telescope.
The Sattelites:
Jupiter has 63 definite satellites. Galileo observed the four biggest: Io, Europa, Ganymede (the biggest satellite in the solar system) and Callisto. He used these to help prove Copernicus's heliocentric model of the Solar System; these moons orbit Jupiter, not the Earth.
Main Fact: It's huge, but nowhere near as huge as the universe, or infinity.
See also: The other planets listed: Saturn and Earth.
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