Jupiter is the largest planet in the Solar System. It is the fifth planet from the Sun. Jupiter is a gas giant because it is large and made mostly of gas.

Jupiter was discovered by Galileo Galilei in 1610 with a small telescope. The planet has a Great Red Spot which is located at 22 degrees south of Jupiter's equator. The great red spot produces wind-speeds up to 432 km/h (268 mph).

By mass, Jupiter's atmosphere is around 76% hydrogen and 24% helium. However, since helium atoms are larger than hydrogen molecules, Jupiter's upper atmosphere is about 90% hydrogen and 10% helium by volume.