Jupiter is the fifth and largest planet in our solar system. This gas giant has a thick atmosphere, 39 known moons, and a dark, barely-visible ring. Its most prominent features are bands across its latitudes and a great red spot (which is a storm).
Jupiter is composed mostly of gas. This enormous planet radiates twice as much heat as it absorbs from the Sun. It also has an extremely strong magnetic field. It is slightly flattened at its poles and it bulges out a bit at the equator.
Jupiter’s diameter is 88,700 miles (142,800 km). This is a little more than 11 times the diameter of the Earth. Jupiter is so big that all the other planets in our Solar System could fit inside Jupiter (if it were hollow).
Jupiter’s mass is about 1.9 x 1027 kg. Although this is 318 times the mass of the Earth, the gravity on Jupiter is only 254% of the gravity on Earth. This is because Jupiter is such a large planet (and the gravitational force a planet exerts upon an object at the planet’s surface is proportional to its mass and to the inverse of its radius squared).
A 100-pound person would weigh 254 pounds on Jupiter.
It takes Jupiter 9.8 Earth hours to revolve around its axis (this is a Jovian day). It takes 11.86 Earth years for Jupiter to orbit the sun once (this is a Jovian year).
Jupiter is made up of gases and liquids, so as it rotates, its parts do not rotate at exactly the same velocity. It rotates very rapidly, and this spinning action gives Jupiter a large equatorial bulge; it looks like a slightly-flattened sphere (it is oblate)
Jupiter is 5.2 times farther from than the Sun than the Earth. On average, it is 480,000,000 miles (778,330,000 km) from the sun.
At aphelion (the place in its orbit where Jupiter is farthest from the Sun), Jupiter is 815,700,000 km from the Sun. At perihelion (the place in its orbit where Jupiter is closest to the Sun), Jupiter is 749,900,000 km from the Sun.
Jupiter has no seasons. Seasons are caused by a tilted axis, and Jupiter’s axis is only tilted 3 degrees (not enough to cause seasons).
Jupiter has four large moons and dozens of smaller ones (there are 39 moons known so far). More moons are being found all the time.
Jupiter has faint, dark rings composed of tiny rock fragments and dust. These rings were discovered by NASA’s Voyager 1 in 1980. The rings were investigated further when Voyager 2 flew by Jupiter. The rings have an albedo of 0.05; they do not reflect very much of the sunlight that they receive.
