Astronomical Facts

Information about the planets is constantly being updated. For example, the number of known Moons for some planets has increased over the years. The following data is current as of 1995.
Average Distance from Sun (Earth=1.0): 5.2
Radius (Earth radii): 11.2
Number of known Moons: 16
Rotation Period (length of day): 0.4 days
Revolutionary Period (length of year): 11.86 years
Mass (Earth masses): 318
Density (g/cm3): 1.3
Atmosphere: 86% hydrogen, 14% helium
Tilt of axis: 3 degrees

Jupiter is the largest planet. Four of Jupiter's moons are visible from Earth with a small telescope. These 4 large moons are called the Galilean moons after Galileo Galilei who observed them in the early 1600's. The names of these 4 large Moons are (Click on the Moons to see a picture of them) Ganymede , Callisto , Io and Europa . Jupiter has a strong magnetic field. Jupiter rotates rapidly, its day being only 9 hours 56 minutes, but Jupiter is not solid, except perhaps at its core, and some parts of Jupiter's surface rotate a little faster than others; this is known as differential rotation. 9 hours 56 minutes is an average rotational speed. Because Jupiter's axis is tilted only 3 degrees from being perpendicular to the plane of its orbit, and its orbit is nearly circular, there is very few seasonal variation on Jupiter. One of the most visible features on Jupiter is its Red Spot, which evidently is a storm similar to a hurricane about the size of planet earth that has been existed for hundreds of years.

Astrological Meaning

Jupiter is the king of the planets. He is in charge of the order of creation. Jupiter shows your values, where you feel confident and in control, and where you feel you have something to teach others. The sign placement of Jupiter shows your values in life.

The house placement of Jupiter shows the area of life you feel luckiest in and the area you receive the most help from other people and from the cosmos. The aspect patterns to Jupiter show the direct network of good and administrative power in your life.

Historical Myth & Legend

The Greek god Zeus in Roman mythology was known as Jupiter. He was the ruler of the other Greek gods, and he often decided matters of justice when a conflict arose between gods or between gods and mortals. Although Zeus held this highest position, he was not without problems of his own. For example, his passions sometimes drove him to become involved in romantic affairs, sometimes secretly, sometimes utilizing deception, trickery or force to get his way, and Zeus sometimes sought the favors of other gods to assist him in the difficult situations that he would find himself in.

The planet Jupiter, like Zeus, leads one to larger and larger arenas, and can bring one great success and authority, but Jupiter is indulgent, and is prone to wastefulness and excess. Not all characteristics of Zeus seem Jupiterian, however. For example, Zeus's use of thunderbolts brings to mind the planet Uranus, so the myths do not always translate simply and directly to astrological terminology. The symbol on the right is the glyph that Uranian astrologers use for the hypothetical planet Zeus.