Planetary magnetism is the study of magnetic fields on planets, moons, and other celestial bodies within our solar system and beyond. These magnetic fields are generated by the motion of liquid metal in a planet's core, and play a critical role in protecting the planet from harmful solar radiation and shaping its atmosphere. Scientists study planetary magnetism to understand how magnetic fields are generated, how they evolve over time, and how they interact with the planet's geology and atmosphere. By studying planetary magnetism, researchers can gain insights into the internal structure and composition of planets, as well as the potential for habitability and the presence of geological activity.