The planet Jupiter isn’t impressive just because of its size--it’s also played an important role in helping us understand our solar system. When Galileo Galilei observed four of Jupiter’s moons in 1610, it was the first observation of moons other than Earth’s. It was also the first observation of celestial motion not centered around our planet; this helped prove Earth is not the center of the universe. Let’s explore this massive planet:

Q: What is Jupiter made of?
A: One of the Gas Giants, Jupiter has a small, dense, hot core surrounded by three layers of hydrogen: a layer of metallic hydrogen, followed by a layer of liquid hydrogen, and finally a layer of gaseous hydrogen. There are no distinct boundaries between the layers; instead, one layer blends into the next.

Q: What’s the Great Spot?
A: Jupiter has massive, permanent storms, some with winds as high as 375 miles an hour. The Great Spot is the most famous of these storms. It is about three times Earth’s diameter, and has been observed for at least three centuries.

Q: How big are Jupiter’s rings?
A: The main ring is about 4,375 miles wide and encompasses the orbits of two of Jupiter’s smaller moons: Adrastea and Metis. The halo stretches from halfway inside the main ring to the tops of the clouds circling the planet, and is faint and about 12,500 miles thick. The outermost ring is extremely faint and stretches beyond the orbit of Jupiter’s moon Amalthea.

Q: How many moons does Jupiter have?
A: Jupiter has 63 moons, and because of this, is sometimes called a mini solar system. Jupiter’s largest moons--Ganymede, Io, Europa, and Callisto--were first observed in 1610, and were the first celestial bodies discovered with a telescope.