At a Glance
- Jupiter’s immense early gravity shaped the Solar System’s structure by influencing planetary orbits and organizing the protoplanetary disk from which planets formed.
- Based on the tilted orbits of its inner moons, Amalthea and Thebe researchers found that early Jupiter had a radius twice its current size and a magnetic field 50 times stronger.
- The study used observable data from moon dynamics and angular momentum instead of uncertain assumptions to estimate Jupiter’s characteristics around 3.8 million years after forming solid bodies.
- These findings support and refine the core accretion model of planet formation, providing new details about how gas giants like Jupiter grow from rocky cores.
- Understanding Jupiter’s early evolution helps scientists study planetary development across the Solar System and informs theories about how other planetary systems might have formed.
Jupiter’s early years played a crucial role in shaping the structure of our entire Solar System. Known as the “architect” of the Solar System, Jupiter’s immense gravity influenced the orbits of other planets and helped define the disk of gas and dust from which they formed. While scientists have long been interested in understanding Jupiter’s formation, a new study offers a clearer picture of the planet’s early size and characteristics. This research, published in Nature Astronomy, sheds light on Jupiter’s size, magnetic field, and other properties shortly after the Solar System began to form.
Led by Konstantin Batygin, a professor of planetary science at Caltech, and Fred C. Adams, a professor at the University of Michigan, the study focused on Jupiter’s moons Amalthea and Thebe, which orbit closer to the planet than its famous Galilean moons. By studying these moons’ slightly tilted orbits, the team calculated that Jupiter’s radius was about twice as large as it is today. This suggests that in its early days, Jupiter was much bigger and had a volume equivalent to over 2,000 Earths. The study also found that Jupiter’s magnetic field was 50 times stronger than it is now.
These new findings come from analyzing the dynamics of Jupiter’s moons and their angular momentum. Unlike previous studies that relied on uncertain assumptions, such as the rate of gas accumulation or the opacity of gas in Jupiter’s early atmosphere, Batygin and Adams used measurable data from the moons’ orbits to understand the planet’s early conditions. Their results suggest that the gas giant’s size and strength were significantly greater when the Solar System’s protoplanetary nebula—the disk of gas and dust around the Sun—dissipated about 3.8 million years after the first solid objects in the Solar System formed.
The researchers’ work builds upon the core accretion model, which explains how giant planets like Jupiter form from a rocky and icy core that quickly gathers gas. This new research refines our understanding of how Jupiter developed and gives scientists a clearer benchmark for studying the evolution of other planets in the Solar System. By enhancing our knowledge of Jupiter’s early years, this study brings us closer to answering fundamental questions about how the Solar System and other planetary systems formed.
References
- Dajose, L. & California Institute of Technology. (2025, May 20). Jupiter was formerly twice its current size and had a much stronger magnetic field, study says. Phys.Org; California Institute of Technology. https://phys.org/news/2025-05-jupiter-current-size-stronger-magnetic.html
- Batygin, K., & Adams, F. C. (2025). Determination of Jupiter’s primordial physical state. Nature Astronomy, 1–10. https://doi.org/10.1038/s41550-025-02512-y
