Jupiter Once Had Double Its Current Size and a Magnetic Field 50 Times Stronger, Research Indicates

Jupiter, the largest planet in our solar system, might have been vastly more substantial and powerful in its early days, according to recent research conducted by astronomers from Caltech and the University of Michigan.

Researchers Konstantin Batygin and Fred Adams suggest that primordial Jupiter was at least twice the size it is today and could have harbored mass equivalent to 8,000 Earths. Beyond its massive size, juvenile Jupiter probably possessed a magnetic field up to 50 times more potent than that of the present day. These magnetic fields, which are unseen forces enveloping planets, interact with charged solar particles and cosmic rays, playing a significant role in the evolution of planets.

To reach their conclusions, the scientists analyzed the movement of Jupiter’s moons and the planet’s rotation. This unconventional approach—bypassing standard planetary formation models—provides fresh perspectives on the early development of the solar system. Jupiter is often dubbed the “architect” of our solar system due to its tremendous gravitational pull, which has been instrumental in shaping the orbits of other planets and dispersing the primordial gas and dust cloud from which the solar system emerged.

“More than any other planet, Jupiter significantly influenced our solar system’s formation,” Batygin remarked in a post on X (formerly Twitter). “However, specifics about its early physical condition remain elusive.”

The study, featured in Nature Astronomy, reflects on a period just 3.8 million years after the first solid objects emerged within the solar system. This was a pivotal time when the gas and dust that formed the planets began to fade, effectively securing the layout of the solar system.

While Jupiter currently boasts nearly 100 moons, Batygin and Adams concentrated on two of its smaller companions, Amalthea and Thebe. These moons orbit at a closer distance to Jupiter than the much larger and geologically active moon Io. Notably, Amalthea and Thebe exhibit unusually tilted orbits, which the researchers believe may reveal secrets about Jupiter’s early dynamics.

As Io gradually moves away from Jupiter—similar to how Earth’s moon is slowly drifting outward—its gravitational force initiates a recoil effect that affects the orbits of smaller moons. By examining these orbital tilts, the scientists could estimate Io’s previous position, thereby determining the outer edge of the gas and dust disk that once enveloped Jupiter.

From this boundary, the researchers deduced Jupiter’s rotation speed during its early years. They concluded that the planet likely rotated once per day, akin to its present rotation speed. Utilizing the physics of rotating bodies, they calculated that Jupiter must have been significantly larger to maintain that spin rate—indicating a young Jupiter that was extremely hot, with temperatures around 2,000 degrees Fahrenheit. In contrast, Jupiter’s current average temperature is a frigid -170 degrees Fahrenheit.

This extreme heat would have led to a substantially stronger magnetic field, aiding the team in estimating how rapidly Jupiter was accumulating gas. Their findings suggest that the planet was increasing in mass at a pace equivalent to one modern-day Jupiter every million years.

“It’s remarkable,” Adams stated, “that even after 4.5 billion years, sufficient evidence exists to allow us to reconstruct Jupiter’s physical condition at the very beginning of its existence.”

This research not only unveils aspects of Jupiter’s enigmatic past but also enhances scientists’ understanding of the processes that influenced the formation of our solar system.