Jupiter Once Twice Current Size with Stronger Magnetic Field

New research led by scientists from Caltech and the University of Michigan reveals that Jupiter was once between two and 2.5 times its present size and had a magnetic field up to 50 times stronger than it does today. This colossal state existed around 4.5 billion years ago, shortly after the solar system began forming, and may have dramatically influenced the orbits of other planets and the structure of the early solar system. The study, published in Nature Astronomy, used the unusual orbits of Jupiter’s small inner moons, Amalthea and Thebe, to estimate the planet’s primordial size and magnetism. These findings underscore Jupiter’s pivotal role in shaping the architecture of the solar system, with its immense gravity and powerful magnetism likely affecting the formation and trajectories of nearby bodies. The research also highlights the challenges posed by Jupiter’s radiation, both past and present, for spacecraft and planetary science. Understanding Jupiter's early history provides crucial insights into the processes that led to the formation of our solar system.