The stunning Jupiter, the most massive planet of the solar system and the fifth in distance from the Sun. It is one of the brightest objects in the night sky; only the Moon, Venus, and sometimes Mars are more brilliant.
When ancient astronomers named the planet Jupiter for the Roman ruler of the gods and heavens (also known as Jove), they had no idea of the planet’s true dimensions, but the name is appropriate, for Jupiter is larger than all the other planets combined. It takes nearly 12 Earth years to orbit the Sun, and it rotates once about every 10 hours, more than twice as fast as Earth; its colourful cloud bands can be seen with even a small telescope.
It has a narrow system of rings and 79 known moons, one larger than the planet Mercury and three larger than Earth’s Moon.
Jupiter has an internal heat source; it emits more energy than it receives from the Sun. The pressure in its deep interior is so high that the hydrogen there exists in a fluid metallic state.
This giant has the strongest magnetic field of any planet, with a magnetosphere so large that, if it could be seen from Earth, its apparent diameter would exceed that of the Moon. Jupiter’s system is also the source of intense bursts of radio noise, at some frequencies occasionally radiating more energy than the Sun.
Despite all its superlatives, however, Jupiter is made almost entirely of only two elements, hydrogen and helium, and its mean density is not much more than the density of water.