Jupiter

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Jupiter, otherwise known as Jove (or Zeus in Greek mythology) was the King of the Gods, the ruler of Olympus and the patron of the Roman state. It is the fifth planet from the Sun, and it is more than twice as massive as all the other planets combined. Jupiter is the fourth brightest object in the sky (after the Sun, the Moon and Venus). It has been known since prehistoric times as a bright "wandering star".

Jupiter has 63 known satellites (as of Feb 2004): the four large Galilean moons, 34 smaller named ones, plus many more small ones discovered recently but not yet named. Here is a picture showing the orbits of some of Jupiter's many moons:

The smaller moons have randomly oriented orbits, meaning they are probably captured asteroids or comets. The larger moons are all in a flat plane around jupiter's equator, just like the planets are in a flat plane around the sun.

Jupiter is one of the "gas giant" planets. The gas giants are planets in our solar system that do not have solid surfaces, their atmospheres simply get denser with depth. What we see when looking at these planets is the tops of clouds high in their atmospheres. Jupiter is about 90% hydrogen and 10% helium with traces of methane, water, ammonia and "rock". This is very close to the composition of the primordial Solar Nebula from which the entire solar system was formed.

The info we know about the insides of Jupiter, like Mars, is mostly educated guesswork, based on some basic facts that we can see from observing it with our telescopes and also information we can gather from studying the way gases behave in a laboratory. Jupiter probably has a core of rocky material amounting to something like 10 to 15 Earth-masses. Above the core lies the main bulk of the planet in the form of liquid metallic hydrogen. This exotic form of the most common of elements is possible only at enormous pressures, which only exist because of Jupiter's size. The outermost layer is composed primarily of ordinary hydrogen and helium. The atmosphere we see is just the very top of this deep layer. Water, carbon dioxide, methane and other simple molecules are also present in tiny amounts.

Jupiter along with other gas planets has high velocity winds (about 400mph) which are confined in wide bands of latitude. Slight chemical and temperature differences between these bands are responsible for the distinct alternating colors. The light colored bands are called zones; the dark ones belts. The colors correlate with the cloud's altitude: blue lowest, followed by browns and whites, with reds highest. Sometimes we see the lower layers through holes in the upper ones. The Great Red Spot (GRS) has been seen by Earthly observers for more than 300 years The GRS is an oval about 12,000 by 25,000 km, big enough to hold two Earths. Current info indicates that the GRS is a high-pressure storm region whose cloud tops are much higher and colder than the surrounding regions. Nobody knows for sure why the GRS has stayed in existence for so long.

Jupiter is just about as large in diameter as a gas planet can be. If more material were to be added, it would be compressed by gravity such that the overall radius would increase only slightly. Stars can be larger only because the tremendous energy released in their cores pushes outward. Jupiter would have to aquire at least 80 times more material than it currently has to become a star.

Jupiter has rings like Saturn's, but much fainter and smaller. They were completely unexpected and only discovered when two of the Voyager 1 scientists insisted that they should at least check to see if any rings might be present. Unlike Saturn's, Jupiter's rings are dark.

When it is in the nighttime sky, Jupiter is often the brightest "star" in the sky (it is second only to Venus, which is seldom visible in a dark sky). The four Galilean moons are easily visible with binoculars; a few bands and the Great Red Spot can be seen with a small astronomical telescope. There's not much of a chance that life exists on Jupiter. Jupiter’s interior is an environment of pressures up to three million times the sea-level pressure on earth, and temperatures as high as 10,000 degrees. It’d be really amazing indeed if any life as we know it, could exist there.



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