Vince Mignogna, age 14, of Pitcairn, Pennsylvania, for his question:

Is it true that Jupiter has 12 moons?

We know today the planet Jupiter has at least 63 moons. The four large ones were discovered in 1610. The others were discovered one by one in later years. In 1951, the number of known Jovian satellites reached a dozen. There may be more than 12, but so far this is all we have been able to find. The last to be discovered is estimated to be about nine miles wide and it orbits its giant planet at a distance of 13 million miles.

The four large Jovian satellites range from almost 2,000 to more than 3,000 miles in diameter. They mere discovered by Galileo, who used a simple little telescope that magnified 31 times. If you have even a beginner's telescope, you can observe these famous Jovian moons. Night by night, you can trace their motions as they orbit around the big planet, each at its own speed and its own distance.  Based on information from various planetary spacecraft here are the latest fact on Jupiter:

        Jupiter's Statistics

        Planetary Symbol: Name in Roman/Greek Mythology: Jupiter/Zeus

        Diameter: 142,800 km (88,736 miles) Rotation Period about Axis: 9.8 hours

        Mass: 1,898 x10^24 kilograms (318 x Earth's)

        Revolution Period about the Sun: 12 years

        Density: 1,326 kg/m^3 Tilt of Axis: 3.1o

        Minimum Distance from Sun: 741 million km (460 million miles)

        Surface Gravity: 23.12 m/s^2 (2.64 x Earth's)

        Maximum Distance from Sun: 817 million km (508 million miles)

        Distance across the Great Red Spot: 40,000 km (24,860 miles)

        Orbital Semi-major Axis: 5.20 AU (Earth=1 AU)

        Temperature at Cloud Tops: -150o C (-101o F)

        Minimum Distance from Earth: 588 million km (365 million miles)

        Average Cloud Top Temperature (K): 123K

        Rings: 1, very thin;  Satellites (moons): 63 known