Its mass is slightly less then 1/1000th of the mass of the Sun, but 2.5 times larger than all the other planets of the Solar System combined. Jupiter's radius is only 10 times smaller than the radius of the Sun. Its mass is 0.001 the mass of the Sun.
This planet has a diameter 11 times bigger than the diameter of the Earth, has a volume of 1,321 Earths, and 318 times as massive. The ratio of mass to volume is so large because Jupiter is mostly gas and liquid.
It is thought that Jupiter has as large of a diameter as a planet of its composition could have. If it had more mass, it would start to shrink.
Jupiter is primarily composed of Hydrogen, but a quarter of its mass is Helium. It is primarily a gas and liquid object, but it possibly has a rocky core consisting of heavier elements. Very small amounts of methane, water vapor, ammonia, silicon-based compounds, carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, sulfur, crystals of frozen ammonia, benzene and other hydrocarbons, have been detected. The famous Great Red Spot observed since the 17th century, is a huge storm on Jupiter, caused by turbulence along the boundaries of the different atmospheric layers.
Moons and... Rings
Jupiter has 64 known moons. Largest of these, Ganymede, is larger than the planet Mercury. Ganymede is also the largest moon in the Solar System, which seems fair.
Jupiter has a faint planetary ring system too. But unlike Saturn, these rings appear to be made up of dust rather than ice. This dust is believed to be material ejected by Jupiter's satellites. Because Jupiter's gravitational pull is much stronger than the pull of its moons, the ejected material is pulled in by Jupiter rather than settling down on the moons. Sounds like a reasonable theory.
The brown/white appearance of Jupiter comes from its clouds, not the land features. This coloration of clouds is caused by upwelling compounds that change color when hit by Sun's ultraviolet rays. The exact make-up of these clouds is unknown, so I would rather not list any guesses. The cloud layer is believed to be about 50 km thick, and to contain at least two decks of clouds. It has been hypothesized that another water-based cloud deck exists beneath the two known decks, because lightning was detected in the planet's atmosphere. The logic behind that is... since lightning is caused by charge separation created by water's polarity, there should be a water cloud layer present. These electrical discharges can be up to 1000 times more powerful than lightning on Earth.
There is no surface on Jupiter, so atmosphere officially ends at the point when the pressure reaches 10 bar.
Jupiter is a planet of great hurricanes. The famous Great Red Spot is so large, it would fit two or three Earths. That storm is located a maximum of 8 km above the surrounding cloud-tops. Mathematical models suggest the storm may be a permanent feature of the planet. The Great Red Spot rotates differentially from the rest of the atmosphere, sometimes slower, sometimes faster. It has traveled around the planet several times in the past couple of centuries it was observed, so it couldn't be any ground feature.
Jupiter has many other brown and white ovals. The white ovals are storms that usually consist of relatively cool clouds in the upper atmosphere. The brown ovals are "warmer" storms inside the "normal cloud layer". These storms can last as little as several hours, and as long as several centuries. In 2000, a new spot nicknamed Red Spot Junior appeared, which was a result of several smaller storms merging into one.
The magnetic field of Jupiter is, for obvious reasons, strongest in the Solar System (besides that of the solar spots). Because it is so strong, it behaves very interestingly. At about 75 Jupiter radii from the planet, the planet's magnetosphere interacts with the solar wind. The solar wind elongates one of the sides of Jupiter's magnetosphere until it nearly reaches the orbit of Saturn. Because the four major moons of Jupiter orbit within the magnetosphere, they are protected from the solar wind. The magnetosphere is also responsible for intense emissions of radio waves from the planet's poles. This energy is transmitted out along a cone-shaped surface. When the Earth intersects with this cone, radio emissions from Jupiter exceed the radio wave emissions from the Sun.
Orbit and Rotation
The average distance between the Sun and the Jupiter is 778 million km, or 5.2 Earth distances, and the giant orbits the Sun once every 11.62 Earth years. The planet's axial tilt is only 3.13 degrees, so there is not much seasonal variation. Being so huge doesn't prevent Jupiter from being the fastest rotating planet in the Solar System. It rotates around its axis in slightly less than 10 Earth hours. Because Jupiter is not a solid body, different parts of its upper atmosphere rotate at different speeds.
Jupiter is the fourth brightest object in the sky, after our Sun, moon and Venus.
Because ancient people, for the most part, walked away from the One God, the Creator, they created many other gods to fill the spiritual void in their hearts. They made gods out of everything around them, including space objects. That is how a Roman god Jupiter, was created.
Earliest know observation of Jupiter is considered to be in the 7th-18th centuries B.C. in ancient Babylonia. Astronomers from all sides of the world observed it too. For example, one of Chinese astronomers made a discovery of one of Jupiter's moons at 362 B.C. Hellenistic astronomer Claudius Ptolemaeus constructed a geo-centric model, determining the orbit of Jupiter to be 11.86 years. An Indian astronomer in 499 A.D. estimated the orbital period to the same 11.86 years. Where there other discoveries in the ancient times? It's quite possible..
Images courtesy of NASA