Jupiter has 80 moons, the second most in the solar system. Of these, 57 have official names, while 23 are awaiting names. Galileo Galilei first observed Jupiter's four largest moons—Io, Europa, Ganymede, and Callisto—in 1610. These moons are the largest in the solar system, with Ganymede being the largest, even bigger than Mercury.

How many of Jupiter's moons have been officially named by the IAU?

• 23

• 57

• 80

• 4

Who first observed Jupiter's four largest moons?

• Galileo Galilei

• Albert Einstein

• Isaac Newton

• Nicolaus Copernicus

Which of the following is NOT one of Jupiter's four largest moons?

• Io

• Europa

• Titan

• Callisto

What is the largest moon in the solar system?

• Ganymede

• Titan

• Europa

• Callisto

Which moon is larger than the planet Mercury?

• Europa

• Io

• Ganymede

• Callisto