NASA / ESA / CSA / Jupiter ERS Team
Jupiter was 2 to 2.5 times larger than it is today – and has had a magnetic field 50 times more powerful. What changes with this discovery?
Planet Jupiter has played a vital role in the evolution of the solar system, according to our current models. On the one hand, it is thought that their formation (about 4.6 billion years ago) and their powerful gravity played a critical role in defining the orbital trajectories of the other solar planets, sculpting the gas and dust disc from which they formed, and influencing the distribution of platesimal platesimal and the formation of the main waist of asteroids.
Jupiter also performed a important role in the appearance of life, when absorbing asteroids that could have had an impact on Earth. Understanding the history of Jupiter’s formation is therefore vital to realize how the primitive solar system evolved.
Konstantin Batygin and Fred C. Adams astronomers published in Nature Recently, on May 20, 2025, a detailed state of Jupiter’s primordial state. Its results indicate that 3.8 billion years after the Solar System, after the formation of the first solids in the Protoplanetary Nebula of the Solar System, Jupiter was 2 to 2.5 times higher than it is today. Also determined that it had a magnetic field 50 times more powerful than the current one.
In heavenly mechanics, the traditional paradigm in which the evolution of the solar system was attributed only to the influence of Jupiter and the sun is deeply rooted. However, observations have increasingly highlighting Jupiter’s importance in the sculpture of solar system architecture.
As such, the complete history of Jupiter’s origins and structural evolution is seen as a fundamental milestone in the initial evolution of the solar system. However, the details and the moment of Jupiter’s formation remain indefinite, largely due to uncertainties inherent in the accentor models.
For his study, Batygin and Adams examined Amalthea and Thebe, two of Jupiter’s inner satellites. This family of satellites is of low mass and orbiting even closer to Jupiter than Io, the smallest and closest orbit closest to Jupiter’s Galilean moons.
Both satellites have slightly inclined orbits and small orbital discrepancies, which allowed Batygin and Adams to calculate Jupiter’s original size. According to your results, Jupiter had in a time a volume of more than 2,000 landsabout twice its current volume of 1,321 lands.
“Our ultimate goal is to understand where we have come from, and determining the early stages of planet formation is essential to solve the puzzles. This approaches us to understand how not only Jupiter has taken shape. What we established here is a valuable point of reference. A point from which we can more confidently rebuild the evolution of our solar system,” Batygin said at Caltech.
This knowledge exceed the traditional uncertainties of planetary training models. These are often based on assumptions about the ability of a gas to absorb or disperse electromagnetic radiation, accretion rates and the mass of the Jupiter core (composed of rock and metal). Instead, the team focused on directly measurable quantities, including the conservation of the angular moment of Jupiter and the orbital dynamics of their moons.
Batygin and Adams analysis provides a crucial image of one of the critical phases of Jupiter’s development, which has been subject to uncertainties in the past. “It is amazing that, even after 4.5 billion years, they subsist enough clues to allow us to rebuild Jupiter’s physical state at the beginning of its existence,” said Adams.
These results can also add new perspectives to theories about planet formation, which may have implications for the study of exoplanets. These theories suggest that Jupiter and the gaseous giants formed as the rocky and cold material (which formed the core of these planets) quickly believed solar nebula.
