You’re looking at its four Galilean Moons, by far the largest of the giant planet’s estimated 79 moons. Their collective name comes from the fact that Galileo first observed them in the year 1609.

Dexter defines The Galilean Suite as tone poems, but while Holst’s inspiration for The Planets was astrological, this work is influenced by what we know about the moons’ geology.

All together, they form a satellite system which is called the Jovian system. The most massive of the moons are the four Galilean moons: Io; Europa; Ganymede; and Callisto, which were independently ...

Galileo’s repeated observations over several nights and realized they were moons orbiting the gas giant. And thus, Io, Europa and Ganymede became known as the Galilean moons of Jupiter.