The giant planet
The giant of the sun’s family is the planet Jupiter. It’s the biggest
planet of the solar system—more than eleven times bigger than the
earth. Jupiter is named after the king of the Roman gods.
The earth, the moon, and Mars are solid rock, but Jupiter is very
different. Although it may have a small rocky core, most of this huge
planet is a ball of hot liquid surrounded by thick clouds of gas. The
clouds form colored bands around the planet. There is also a strange
spot called the Great Red Spot. It seems to be an enormous humcane, more
than three times as wide as the earth is thick. It has been whirling in
Jupiter’s atmosphere for hundreds of years. And other wild windstorms
are always raging in Jupiter’s thick clouds.
Jupiter has sixteen moons. The smallest moon isn’t as big as most of the
earth’s mountains. The biggest, called Ganymede, is bigger than the
planet Mercury. One moon, called Io, has erupting volcanoes.
Jupiter is surrounded by a very thin ring of dust. This ring may be what
is left of a moon that came too close to Jupiter. The tremendous pull of
Jupiter’s gravity would have torn it apart.
Jupiter is about 484 million miles (778 million kilometers) from the
sun. A year on Jupiter is about 12 earth-years long, but a day is only
about 10 hours.
Scientists have used space probes to study Jupiter. In 1977, Voyager 1
and Voyager 2 were launched in the United States. Both probes flew
past Jupiter and Saturn. Voyager 1 found Jupiter’s ring, and Voyager
2 photographed the four largest moons.
