JUPITER

Jupiter is the biggest planet in our Solar System, eleven times bigger in diameter than Earth and two and a half times more massive than all the other planets put together. Jupiter has no solid surface. Beneath the gas clouds lies hot, liquid hydrogen, then a layer of hydrogen in a form similar to liquid metal, and finally a rocky core. Jupiter has a faint ring around its equator made of microscopic dust particles.

Table 14. ESSENTIAL DATA

Diameter at equator142,984 km (88,849 miles)
Average distance from Sun778.4 million km (483.7 million miles)
Orbital period11.87 years
Rotation period9.93 hours
Mass (Earth=1)318
Gravity (Earth=1)2.36
Cloud-top temperature-110°C (-166°F)
Number of moonsAt least 63

THE GALILEAN MOONS

In 1609, the Italian astronomer Galileo first spied Jupiter’s four largest moons: Io, Europa, Ganymede, and Callisto. The largest Galilean moon, Ganymede, with a diameter of 5,268 km (3,273 miles), is also the biggest moon in the Solar System.

JUPITER’S ATMOSPHERE

Alternate dark and pale bands streak Jupiter’s atmosphere. The dark bands are called belts and the pale ones are called zones. The different colours reflect the presence in the atmosphere of different chemicals, such as sulphur, ammonia, and phosphorus compounds.

THE GREAT RED SPOT

For over 300 years astronomers have observed Jupiter’s Great Red Spot. Space probes have shown it to be a violent super-hurricane, where winds swirl anticlockwise at high speeds. It measures around 40,000 km (25,000 miles) across.

JUPITER’S LIGHTS

There are light displays, called auroras, at Jupiter’s poles, like the Northern and Southern Lights we see on Earth. But on Jupiter the displays are much more dramatic. Lightening bolts 10,000 times more powerful than any seen on Earth also light up the planet.

Copyright © 2007 Dorling Kindersley