Jupiter, the colossal gas giant of our Solar System, may have been even more massive in its youth.
According to a new study published in Nature Astronomy, around 3.8 million years after the Solar System began to form, Jupiter could have been 2 to 2.5 times larger in volume than it is today, with a magnetic field up to 50 times stronger.
This conclusion comes from researchers Konstantin Batygin (Caltech) and Fred Adams (University of Michigan), who examined the unusual, tilted orbits of Jupiter’s inner moons—Amalthea and Thebe. These tiny satellites carry important clues about Jupiter’s early structure and helped scientists trace back the planet’s evolutionary path.
Their findings reinforce the core accretion theory, which posits that gas giants begin as solid rocky cores and quickly gather gas once they surpass a certain size threshold.
Jupiter’s rapid growth not only influenced its own development but also shaped the broader layout of our Solar System. As the surrounding gas thinned out, Jupiter contracted under its own gravity to reach its present-day size.
Despite its early bulk, Jupiter never came close to becoming a star—it would’ve needed at least 85 times its current mass to ignite fusion. Still, this study marks a major step in understanding how massive planets form and how they shape their cosmic neighborhoods.
RESEARCH PAPER
Konstantin Batygin & Fred C. Adams, “Determination of Jupiter’s primordial physical state”, Nature Astronomy (2025)
Jupiter, the colossal gas giant of our Solar System, may have been even more massive in its youth.
According to a new study published in Nature Astronomy, around 3.8 million years after the Solar System began to form, Jupiter could have been 2 to 2.5 times larger in volume than it is today, with a magnetic field up to 50 times stronger.
This conclusion comes from researchers Konstantin Batygin (Caltech) and Fred Adams (University of Michigan), who examined the unusual, tilted orbits of Jupiter’s inner moons—Amalthea and Thebe. These tiny satellites carry important clues about Jupiter’s early structure and helped scientists trace back the planet’s evolutionary path.
Their findings reinforce the core accretion theory, which posits that gas giants begin as solid rocky cores and quickly gather gas once they surpass a certain size threshold.
Jupiter’s rapid growth not only influenced its own development but also shaped the broader layout of our Solar System. As the surrounding gas thinned out, Jupiter contracted under its own gravity to reach its present-day size.
Despite its early bulk, Jupiter never came close to becoming a star—it would’ve needed at least 85 times its current mass to ignite fusion. Still, this study marks a major step in understanding how massive planets form and how they shape their cosmic neighborhoods.
RESEARCH PAPER
Konstantin Batygin & Fred C. Adams, “Determination of Jupiter’s primordial physical state”, Nature Astronomy (2025)
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