Jupiter has (at last count) 79 moons. The four Galilean moons make up over 99.9% of the mass of all of the planet’s satellites. The next largest moon Amalthea was discovered in 1892. It’s irregularly shaped, 250 × 146 × 128 km, and not much was know about until the Voyager 1 and 2 flyby of Jupiter in 1979 and the Gailieo order mission which did a close pass by the moon in 2002.
Image Credit: NASA