The Jupiter

Jupiter is by far the largest planet within our Solar System: two and a half times larger than all of the other planets put together. It is the fifth planet from the Sun and one of the brightest planets. Jupiter is sometimes called a "gas giant" because most of this planet is made up of liquid and gas.
How big is the planet?
Jupiter is 142,984 km or about 11 Earths in diameter at the equator. That makes it about one tenth as big as the Sun! You could fit about 1,400 Earths into the volume of Jupiter. It is 133,709 km or 10 Earths in diameter from pole to pole. Jupiter's rapid rotation makes it bulge out at the equator.
Jupiter's magnetic field is the largest single planetary thing in the Solar System. It is 26 million kilometers across, making it about 20 times bigger than the Sun. It has a tail that extends past Saturn's orbit. If it could be seen from Earth, it would appear to be five times the size of the full moon.

Surface of Jupiter

What is the surface like on Jupiter ?

The surface we see is not solid. This enormous planet has a relatively small solid and rocky core. Liquids and gases surround this core and blend with the atmosphere.
Jupiter is a cloudy, windy and stormy planet. It is always covered by a layer of clouds, and wind speeds of 600 km/h are not uncommon. The storms are visible as swirls, bands and spots. A particularly violent storm, about three times Earth's diameter, is known as the Great Red Spot. This storm has been in existence for nearly 300 years!
The layer of clouds is divided into several bands. The lighter colored bands are called zones and the darker bands are called belts. The colors are caused by small changes in the temperature and chemistry. Each band rotates in the opposite direction from its neighbors. Along the edges where the bands meet, these winds collide and create swirling patterns.
The stormy atmosphere of Jupiter has flashes of lightning just like on Earth. However these can be up to 100 times more powerful. The lightning is made by water near the tops of the clouds.

Rings Of Jupiter

What are its rings like?

Jupiter's rings are dark and hard to see. They are made of tiny particles that meteors knocked off Jupiter's small inner moons and debris left over from comets and other objects that came close to the surface of Jupiter. In fact, until the Voyager spacecraft arrived near Jupiter and took closeup pictures of the rings of Jupiter, scientists didn't even know that it even had rings at all. Two rings are clearly from material that can be associated with two sets of the inner moons of the planet.

Moons In Jupiter

What are its moons like?

Jupiter has 63 known moons. There are four major moons that were discovered by Galileo in 1610. Those moons are Io, Europa, Ganymede and Callisto. They are called the Galilean moons. There are often eclipses on Jupiter's cloud tops by the Galilean moons.
Amalthea GroupThere are four small moons orbiting inside Io's orbit. That group is called the Amalthea group because Amalthea is the largest one. They are all small and potato shaped. Amalthea is very red. The material of Jupiter's rings came from meteors knocking it off of those moons.

Io

Io is Jupiter's closest major moon. It is 3643.2 km across, slightly larger than Earth's Moon. It has volcanoes and molten sulfur lakes. There are not very many craters if there are any at all because the volcanic activity would cover them up. Io has an iron and maybe iron sulfide core at least 1800 km across. It is surrounded by a silicate shell. There is little water on Io. Maybe it was because when Jupiter was forming, it was hot enough to dry out Io, but not the other major moons. In Roman mythology Io was a beautiful young woman that Jupiter loved.

Europa

Europa is 3,121.6 km across, about ten percent smaller than Earth's Moon. It is made of silicates and has a layer of smooth water ice 10 to 30 km thick. The ice has long cracks in it and very few craters. It looks like the sea ice on Earth. The ice had slid around at the cracks. There is liquid water under the ice up to 100 km below the surface. There are also some large spots on the surface. In Roman mythology Europa was courted by Jupiter in the form of a bull.
Jupiter as seen by the space probe "Cassini". This is the most detailed color portrait of Jupiter ever assembled.

Ganymede

Ganymede is 5262.4 km across, making it 380 km wider than Mercury. It is Jupiter's largest moon and the largest moon in the Solar System. It had plate tectonics like Earth. There are older darker regions and newer areas with grooves where the plates moved. Newer craters have bright rays around them from material thrown up by impacts. Older craters look flat and faded because the icy surface does not hold the shape of the crater as well as rock does over long periods of time. Ganymede may have an iron and sulfur core with a silicate mantle and an icy shell. It may be like Io except with a layer of ice on it. In Roman mythology Ganymede was a beautiful young man who Jupiter kidnapped and made cupbearer to the gods on Mt. Olympus.

Callisto

Callisto is 4820.6 km across, about the same size as Mercury. It has many craters. Like craters on Ganymede, the older craters had faded. The largest crater is Valhalla. It has a bright center 600 km across with rings around it up to 3000 km across. Callisto is made of silicates and ice. There is a 200 km thick icy crust with a liquid water sea under it. In Roman mythology Callisto was turned into a bear by Jupiter's jealous wife Juno. Later Jupiter placed her in the stars as The Great Bear.
Other moonsThe other moons are tiny ones in several groups outside the orbits of the

A Day,Year and Gravitational Pull

How long is a day on this planet?

One Jupiter day is about 10 Earth hours long. You have to say "about" because different parts of Jupiter rotate about its axis at different speeds. This is caused by the fact that Jupiter is mostly gases that are in constant motion and sometimes going in opposite directions. Some efforts have been made to try and measure the rotation speed of the inner rocky core of Jupiter, but that has proved to be quite difficult to accomplish due to the magnetic fields that surround Jupiter and the very active radio energy that is generated by the atmosphere of Jupiter, which interferes with measuring techniques like radar that has been used to measure the surface of Venus and Mars.

How long is a year on this planet?

The Great Red Spot Jupiter EclipsesOne year on Jupiter is 4,335 Earth days or 11.87 Earth years long.
A Jupiter year is about equal to four-tenths (or two-fifths) of a Saturn year. Thus after every two Saturn years, Jupiter has completed five full orbits about the Sun. So after 59 years, Saturn and Jupiter will be back in nearly the same position. When the orbits of two planets are simple ratios of each other like this, it is called a resonance.

How much would Jupiter's gravity pull on me?

If you were floating close to the cloud tops of Jupiter, it would pull you down with a force about two and a half times as strong as the force of Earth's gravity.
Jupiter's rapid rotation causes the equator to bulge out. This would also cancel out about 10 percent of gravity's force on you if you were at the equator. The amount of this counteraction becomes lower the closer you get to the poles.

Jupiter - Who is it named after?

Who is it named after?

Statue of Zeus (Jupiter) in Olympia, Greece
Jupiter is named after the chief of the Roman gods, also called Zeus in ancient Greece. It was so named because of the planet's enormous size, which dominates all the others.

Asteroid Belt

Asteroid Belt Intorduction

The largest asteroid in the solar system is 2001 KX76. In the asteroid belt, the largest asteroid is Ceres, which is 933 kilometers across. The next largest, which is called Vesta, is 530 kilometers across.
Some asteroids are less than a kilometer across. Unofficially the limit has been set at 50 meters, and anything smaller than that is going to be simply called a meteoroid. With advances in telescopes and particularly for objects that travel close to the Earth, some objects smaller than 50 metres have indeed been seen passing nearby the Earth.
There are probably several million asteroids in the solar system. Over 96,000 asteroids have been given numbers. Almost 12,000 of them have names. But even though there are a lot of asteroids, the asteroid belt is mostly empty space. Traveling through the asteroid belt in a space ship would not be very much like what you see in a science fiction film.
The asteroid belt lies between the planets Mars and Jupiter. It contains lumps of rock and metal much smaller than planets. These lumps are called asteroids or minor planets. They are not visible from Earth with the naked eye, but many may be seen through binoculars or small telescopes.

Asteroid Belt Names After
The first asteroids were named after mythical heroes and gods much like the major planets. The first to be discovered was named Ceres after the Roman goddess of growing plants (particularly grain) and of motherly love. The second asteroid discovered was called Pallas and was named after one of the Greek gods of wisdom. Asteroids are also given a number in the order of their discovery, so Ceres is 1, Pallas is 2, and so forth.
As the number of known asteroids increased, they ran out of mythical names so other names were used instead. Some asteroids were named after countries. For example asteroid number 136 is named Austria. Others were named after plants, for example 978 Petunia. 1620 Geographos was named after the National Geographic Society, in recognition to their efforts at sharing knowledge about the Solar System. Many are named after people, both alive and dead. In a couple of cases, like 2309 Mr. Spock, asteroids were named after the discover's pet cat. This last type of naming is discouraged, but it still happens from time to time. Even fictional characters have been used.
Today, names for asteroids can be suggested by the people who discover them. The names become official after a group of people reviews them to make sure they are not offensive or too much like another name. Because so many asteroids are now being found, most new asteroid discoveries are not even getting a name at all, but rather a numbered code. It is not likely that they will ever be given a formal name, at least in this century.

Asteroid Belt Discovery
Asteroid Belt Facts:
1.The total weight of all the asteroids in the asteroid belt is about 1/35th of that of our moon. 2.Its largest object in the asteroid belt, Ceres, makes about 1/3 of the total weight of all the asteroids. 3.Ceres is the only dwarf planet in the asteroid belt.
The first asteroid to be discovered was Ceres, on 1 January 1801, by Giuseppe Piazzi accidentally. At first he thought this was a comet, then later a planet! When it was realised it was too small Sir William Herschel (the astronomer who discovered Uranus) made up the word "asteroid" to describe it, using the Latin word aster, meaning star, and the -oid, meaning rock or planet. In other words a star-like planet, because he couldn't see any details due to the small size of the object.
By 1807 another 3 asteroids were discovered, but no more were found until 1845 when a persistent asteroid hunter named Karl Ludwig Hencke found a fifth, and sixth asteroid in 1847. Ever since then at least one new asteroid has been found each year.
In 1891, the first pictures of the night sky were taken to find more asteroids. This led to the discovery of many more asteroids. A picture of the same part of the sky is taken on two different nights. When the two pictures are lined up, the stars will be in the same places but an asteroid will have moved.
In our modern times, over 280,000 asteroids have been discovered. Many more are being found all the time. Some of these asteroids pass near the earth and astronomers want to find any that come close to our planet. Large numbers of asteroids are now being discovered by machines.

Asteroid Belt is Made Of?
Three out of four asteroids are made of rock that is rich in carbon. The rest are made of the metals iron and nickel. About half of these are pure iron and nickel; the rest are mixed with compounds of silica, the element that makes up rocks. Each of the larger metal asteroids contains huge amounts of iron: much more than is mined every year on Earth.
Scientists are very interested in what asteroids are made of because it can help them learn how the solar system was formed. Several spacecraft have visited asteroids to learn more about themAre there asteroids outside of the asteroid belt?Most asteroids are found in the asteroid belt, but not all. Some asteroids orbit closer to the Sun, and many asteroids orbit beyond Neptune. Asteroids that closely approach Earth are called Near-Earth Asteroids. Sometimes pieces of asteroids strike the Earth, burning in the atmosphere as a meteor. If they are large enough, they might actually hit the surface and become meteorites.
Asteroid Ida and its moonThere are also some asteroids in the outer solar system that are called Centaurs. But it is hard to tell whether any one Centaur is an asteroid, comet, or Kuiper Belt object. For example, the first Centaur to be discovered was Chiron. But some scientists think it is a comet, not an asteroid. Officially it is called both the asteroid 2060 Chiron and the comet 95P/Chiron!
In most cases when an the orbit of asteroid crosses the path of a planet such as Jupiter, at some point the asteroid will either hit the planet or else be hurled into another orbit. Many of the small moons of some planets may have once been asteroids that were captured by the planet's gravity when they came too close. However there are two points along the orbit of a planet were an asteroid can safely linger. These are found at a point one-sixth (or 60°) of an orbit ahead of the planet, and the same distance behind the planet. These sites are called Lagrange points, and they are found where the force of gravity from the Sun and the planet balance out with the motion of the asteroid's orbit. The asteroids found in these spots are called Trojans, and they move around the Sun at the same velocity as the planet.

Famous Asteriods
The dwarf planet Ceres.2001 KX76 is now the biggest asteroid in the solar system, beating out Ceres. Ceres is one of the few asteroids that is shaped like a sphere, and it may have some ice just underneath its dusty surface.
The asteroid Ida has its own moon named Dactyl. A number of asteroid moons have now been found.