The Galilean Moons of Jupiter

Abstract

In the previous chapter, the three Keplerian laws were described and the first two were demonstrated qualitatively in the context of the orbit of Earth’s Moon. Kepler discovered the basic orbital descriptions by studying the planets, particularly the planet Mars. Kepler’s laws are applicable, however, to the satellites of the planets (as well as to binary stars, to which they will be applied in later chapters). Because we observe the motions of the other planets from an unfavorable perch on our own moving planet, their movements in our sky are somewhat complicated (see Chapters 7 and 8). Consequently, the brightest of Jupiter’s moons are incomparably better for demonstrating the third Keplerian law quantitatively.