doi.org/10.1038/s41550-025-02512-y
Credibility: 589
#Jupiter
Jupiter, the largest planet in the Solar System, may have once been more than twice as big as it is today, with a magnetic field up to 50 times stronger, according to scientists who studied its tiny inner moons
These discoveries offer unique and valuable insight into how Jupiter – and the entire Solar System – formed.
Jupiter – An Even Bigger Giant in the Past
Jupiter is already known as the “heavyweight champion” of the Solar System, but new research suggests it was even more impressive in the past.
Scientists believe Jupiter played a key role in the formation of the Solar System.
Its strong gravity shaped the orbits of other planets, helped create the asteroid belt, and may even have protected Earth by deflecting dangerous asteroids.
Uncovering Jupiter’s Ancient Power
A new study led by astronomers Konstantin Batygin of Caltech and Fred C.
Adams of the University of Michigan has revealed that Jupiter was once between two and two and a half times its current size.
In addition, its magnetic field was incredibly stronger, up to 50 times stronger than it is today.
These discoveries help us understand what the Solar System was like in its early, chaotic and crucial time in its formation.
The study, titled “Determining the Early Physical State of Jupiter,” was published May 20, 2025, in the journal Nature Astronomy.
Rethinking the Formation of the Solar System
For a long time, scientists thought that the Solar System was shaped primarily by the Sun and Jupiter.
However, understanding exactly how Jupiter formed has always been elusive, due to uncertainties about how giant planets like it develop.
These uncertainties involve questions such as how much gas Jupiter managed to capture, how fast it grew, and the size of its core, made of rocks and metals.
Jupiter’s Moons Hold Ancient Secrets
To solve this mystery, Batygin and Adams studied Amalthea and Thebe, two small moons that orbit very close to Jupiter, even closer than Io, one of the Galilean moons.
These moons have slightly tilted orbits and small irregularities, which allowed scientists to calculate Jupiter’s original size.
They found that the planet once had a volume equivalent to more than 2,000 Earths, about twice its current volume of 1,321 Earths.
As Batygin put it, “We want to understand where we came from, and figuring out how the planets formed is an essential piece of that puzzle.
This study helps us understand not just Jupiter, but how the entire solar system took shape.”
A New Starting Point for Planetary Science
These findings are important because they avoid the uncertainties common in planet formation models, which rely on hard-to-confirm assumptions, such as how gas interacts with radiation or how fast a planet grows.
Instead, the scientists used more concrete data, such as the motion of Jupiter’s moons and the conservation of its rotational energy.
The study also sheds light on a crucial moment: when the cloud of gas and dust that formed the planets, called the solar nebula, disappeared.
This was a turning point, when the “building blocks” of the planets disappeared, and the early structure of the solar system began to form.
“It’s amazing that after 4.5 billion years, there are still clues that allow us to reconstruct what Jupiter was like at the beginning of its existence,” Adams said.
Impacts Beyond the Solar System
These findings may also help us understand how other planets, including those outside our solar system (called exoplanets), form.
The research confirms that Jupiter and other gas giants began as rocky and icy cores that quickly attracted gas from the solar nebula.
With more precise measurements of Jupiter’s size, rotation and magnetic field in its early stages, scientists now have a stronger foundation for studying planet formation throughout the universe.
Published in 05/27/2025 00h04
Text adapted by AI (Grok) and translated via Google API in the English version. Images from public image libraries or credits in the caption. Information about DOI, author and institution can be found in the body of the article.
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