Jupiter is the largest planet in our solar system. It is a gas giant made primarily of hydrogen and helium gases that appear yellowish on the outside. In the center, the gases are compressed into a dense, chewy caramel-like state. Jupiter has 16 moons and has a day that is just under 10 hours and takes nearly 12 of our years to orbit the sun. Over 1,300 Earths could fit inside Jupiter, which is large enough to swallow our planet.