The Third Law of Kepler at different scales: from moons to galaxies

This article aims to verify Kepler’s Third Law for different astronomical systems across various distance scales, such as Jupiter and its four Galilean moons, as well as the Solar System, exoplanets, and galaxies. In the case of Jupiter, we used real and simulated data using the Contemporary Laboratory in Astronomy (CLEA) program, using the equivalence between Simple Harmonic Motion (SHM) and Uniform Circular Motion (UCM). For the Solar System and exoplanets, we employed data from NASA’s space missions, and for galaxies, we utilized data regarding the motion of nearby stars around the Sagittarius A* black hole in the Milky Way. Kepler’s law is verified at lunar, planetary, and exoplanetary scales and is also approximately satisfied for Sagittarius A*. However, Kepler’s Third Law does not hold for the overall motion of stars around galactic centers, as the rotation curves of galaxies exhibit behavior different from that predicted by the inverse square law. It is possible that the influence of dark matter may be dominant in these systems.

Keywords:
Physics; astronomy; Galilean moons; exoplanets; galaxies