New research suggests that Jupiter, the largest planet in our solar system, was once even bigger—about twice its current size—and had a magnetic field 50 times stronger than it does today.
This discovery is giving scientists valuable insight into how Jupiter and the rest of our solar system formed billions of years ago.
The study, published in Nature Astronomy, was led by Professor Konstantin Batygin of Caltech and Professor Fred C. Adams of the University of Michigan.
Their work focuses on Jupiter’s early life, around 3.8 million years after the first solid materials began forming around the young Sun.
At that time, the solar system was still surrounded by a swirling cloud of gas and dust known as the protoplanetary nebula. As that nebula faded, it marked a key turning point in the formation of the planets.
To understand what Jupiter was like back then, Batygin and Adams looked at two of its tiny inner moons—Amalthea and Thebe—which orbit even closer to the planet than the well-known Galilean moons like Io.
These two moons have slightly tilted orbits, and those tilts offer clues about Jupiter’s ancient size and strength.
By analyzing their movements, the researchers were able to work backward and estimate that Jupiter was once about twice as wide as it is today and had a much more intense magnetic field.
One of the most remarkable aspects of the study is that it relies on real measurements of Jupiter’s current moons and spin, rather than assumptions used in traditional planetary models.
Most planet formation theories involve many variables, like how fast gas was pulled in or how much heavy material a planet’s core contains.
Batygin and Adams, however, focused on data that can be directly observed—such as the planet’s angular momentum (its rotation and mass distribution) and the orbits of its moons—to get a clearer picture.
Their findings help confirm theories about how Jupiter formed, particularly the core accretion model, which says that gas giants like Jupiter began as rocky or icy cores that rapidly gathered gas from the surrounding nebula.
This process likely shaped not just Jupiter, but many giant planets found in other solar systems.
By revealing what Jupiter looked like at this critical early stage, the study helps us better understand how the solar system settled into its current structure.
Jupiter’s massive gravity likely influenced the positions and paths of other planets, acting like a cosmic architect.
Now, with these new clues, scientists are one step closer to understanding where we came from—and how the planets we know today came to be.
Source: KSR.
