Determination of Jupiter's Primordial Physical State

TL;DR

This study reconstructs Jupiter's early physical state, revealing it was significantly larger, had a stronger magnetic field, and was actively accreting material shortly after the solar system's formation, aligning with core-accretion models.

Contribution

It introduces a novel method combining satellite dynamics and angular momentum to infer Jupiter's primordial size and interior conditions.

Findings

Jupiter was 2 to 2.5 times larger than today 3.8 million years after formation.

Jupiter's magnetic field was approximately 21 mT, about 50 times stronger than current.

Jupiter was accreting material at 1.2-2.4 Jupiter masses per million years.

Abstract

The formation and early evolution of Jupiter played a pivotal role in sculpting the large-scale architecture of the solar system, intertwining the narrative of Jovian early years with the broader story of the solar system's origins. The details and chronology of Jupiter's formation, however, remain elusive, primarily due to the inherent uncertainties of accretionary models, highlighting the need for independent constraints. Here we show that by analyzing the dynamics of Jupiter's satellites concurrently with its angular momentum budget, we can infer Jupiter's radius and interior state at the time of proto-solar nebula's dissipation. In particular, our calculations reveal that Jupiter was $2$ to $2.5$ times as large as it is today, 3.8 million years after the formation of the first solids in the solar system. Our model further indicates that young Jupiter possessed a magnetic field of approximately $B_{\rm{J}}^{\dagger} \approx 21$ mT (a factor of $\sim50$ higher than its present-day value) and was accreting material through a circum-Jovian disk at a rate of $\dot{M} = 1.2-2.4$ Jupiter masses per million years. Our findings are fully consistent with the core-accretion theory of giant planet formation and provide an evolutionary snapshot that pins down properties of the Jovian system at the end of the protosolar nebula's lifetime.