These facts about Jupiter are aimed at giving you an overview of this familiar planet. Existing in our solar sysyten, Jupiter is the 5th planet from the Sun. To the unaided eye, Jupiter, named for the chief of the Roman gods, appears in the sky as a bright yellowish object.
1. Constellations and brightness
It travels slowly through the 12 constellations of the zodiac and completes the circuit in just under 12 years. Only one star, Sirius, and the planet Venus outshine Jupiter (the planet Mars, at some favourable oppositions, also is brighter).
The rotational period of Jupiter varies with the latitude – it is shortest at the equator (9 hours, 50 minutes, 30 seconds) and longer north and south of the equator.
Jupiter is by far the largest planet in our Solar System, with a mean diameter of 85,680 miles (the man diameter of the Earth is only 7,900 miles).
Jupiter is less dense than the terrestrial planets, being only about ¼ the density of the Earth. Most of its volume is made of hydrogen (like the Sun) in both a liquid metallic and gaseous state. The liquid metal core of hydrogen is believed to extend out to a distance of 40,000 miles from Jupiter’s centre. These gases may surround a small rocky core.
As the planets formed 4.6 billion years ago, cooler temperatures in the outer solar nebula prevented much of the primordial hydrogen and some helium from being heated and vaporized. The gravitational pull of this larger mass of gas was able to attract even more hydrogen and helium from neighbouring space, contributing to the gaseous atmospheres of the outer planets – including Jupiter.