Determination of Jupiter’s Primordial Radius, Accretion Rate, and Magnetic Field

Jupiter's formation significantly influenced the structure and evolution of our solar system, yet crucial details about its earliest physical state remain uncertain due to the complexity of planet-formation models. Here we will discuss Jupiter's primordial physical state by leveraging the dynamical history of Jupiter’s innermost satellites and the planet’s angular momentum budget. In particular, our analysis indicates that at the time the solar nebula dispersed, Jupiter was 2 to 2.5 times its current size. Furthermore, during this epoch, Jupiter had a magnetic field of at least ~200G, and it was accreting gas through a circumplanetary disk at a rate of about one to two Jupiter masses per million years. These findings support core-accretion models of giant planet formation and offer a critical snapshot of Jupiter's properties at a pivotal stage of the solar system's evolution, providing new insights into the conditions that shaped the largest planet of the sun's planetary album.