Galilean
Jupiter's four largest moons are known as the Galileans. They are individually named Io, Europa, Ganymede, and Callisto, named my Simon Marius in 1610. Ganymede is the largest of these four moons.
Io
He could only make out four of Jupiters' largest moons.
Ganymede is Jupiter's largest moon. The top four of its largest moons are Europa, Io, Callisto, and Ganymede.
The four largest moons of Jupiter discovered by Galileo are Io, Europa, Ganymede, and Callisto.
Jupiter's largest four moons, called the Galilean satellites because Galileo was the first person to see them, are Europa, Io, Callisto and Ganymede.
Io, the innermost of Jupiter's four largest moons, appears the brightest from Jupiter's surface due to its proximity to the planet and its reflective surface.
Its Calisto,Ganymede,Europa, and Io
Galileo was the first to observe the 4 largest moons of Jupiter (which are still known as the Galilean moons, in his honor).
Collectively, they are known as the Galilean moons. Individually, they are Calypso, Ganymede, Io, and Europa.
The four largest moons of Neptune include Triton, Nereid, Naiad, and Thalassa. The next largest moons are Despina, Galatea, Larissa, and Proteus.
Europa is one of Jupiters moons. Jupiter has many moons, but Europa is one of the four large moons that was discovered in 1610 by Galileo Galilei (and possibly independently by Simon Marius around the same time).