Jupiter was once massive enough to hold 2,000 Earths says research

Astronomers have made an astonishing discovery that Jupiter, the biggest planet of our solar system, was once so colossal it could have enveloped 2,000 Earths. Jupiter takes the crown as the most ancient planet in our system, having emerged from the cosmic detritus that remained after the Sun's birth 4.6 billion years ago.

The gas giant's girth is a staggering 11 times that of Earth, which NASA likens to comparing a grape to a basketball in terms of size. Indeed, Jupiter's mass is a hefty 2.5 times that of all other planets in the solar system put together.

Yet, fresh research has unveiled that Jupiter's past form was even more immense than its current state – complete with a far mightier magnetic field. "Our ultimate goal is to understand where we come from, and pinning down the early phases of planet formation is essential to solving the puzzle," explained Caltech's planetary science professor Konstantin Batygin.

"This brings us closer to understanding how not only Jupiter but the entire Solar System took shape." To unravel the mysteries of Jupiter's growth and subsequent shrinkage, astronomers Batygin and Fred Adams from the University of Michigan studied the planet's diminutive moons, Amalthea and Thebe, reports the Manchester Evening News.

With a tally of 95 known moons, Jupiter ranks second in the solar system's moon count. It trails behind Saturn's impressive collection of 274. Amalthea and Thebe are the tiniest and closest companions among Jupiter's four major Galilean moons.

Researchers have delved into the orbital dance of Jupiter's moons to deduce the gas giant's past enormity, revealing that a mere 3.8 million years after the Solar System's first solids took shape, Jupiter was already bulking up to 2 to 2.5 times its present mass. They also discovered that back then, its magnetic field was a whopping 50 times more potent than it is now.

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"It felt remarkable that two relatively minor moons provided such clear evidence of Jupiter's early state," Batygin confessed to Space.com. "The real excitement was achieving this result independently of complex accretion models that depend on a series of assumptions."

Adams marvelled: "It's astonishing that even after 4.5 billion years, enough clues remain to let us reconstruct Jupiter's physical state at the dawn of its existence."

So why has Jupiter been on a slimming trend?

The study suggests that Jupiter's once mighty magnetic field yanked in material from its surroundings, beefing up the planet by approximately 1.2 to 2.4 Jupiter masses every million years. But as the cosmic buffet ran out, Jupiter's own gravitational pull made it contract, thus becoming more compact and spinning up its rotation rate.

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Jupiter continues to gradually shrink even today. As its surface and core cool down, the core compresses and heats up, causing the planet to slowly bleed energy.

This intriguing research has been detailed in the journal Nature Astronomy.