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5 days ago
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Jupiter designed the solar system. Here's what the planet was like as a child.
Jupiter, the largest planet orbiting the sun, used to be much bigger and stronger when the solar system was just beginning to take shape, a pair of astronomers say. Two scientists at Caltech and the University of Michigan suggest that early Jupiter was at least double its contemporary size. The primitive version of the gas giant could have held some 8,000 Earths within it, said Konstantin Batygin, lead author of the new study. What's more, young Jupiter probably had a magnetic field 50 times more powerful. A magnetic field is an invisible force surrounding a planet that interacts with charged particles coming from the sun and cosmic rays. To calculate those measurements, the scientists looked at how Jupiter's moons move through space and how the planet spins. This unconventional approach, which didn't rely on traditional models, may fill gaps in the solar system's history. Many scientists refer to Jupiter as the "architect" of the solar system because its immense gravity influenced the orbits of other planets and carved up the cloud from which they all emerged. "More than any other planet, Jupiter played a key role in shaping our solar system," Batygin said in a post on X. "Yet details of its early physical state are elusive." SEE ALSO: Private spacecraft circling moon snaps photo with strange optical illusion NASA's Juno spacecraft snaps images of Jupiter and catches the tiny moon Amalthea as it orbits the planet. Credit: NASA / JPL-Caltech / SwRI / MSSS / Gerald Eichstädt The paper, published in the journal Nature Astronomy, rewinds the clock to just 3.8 million years after the first solid objects formed in the solar system and the cloud of gas and dust from which everything formed started to evaporate. This period — when the building materials for planets disappeared — is thought to be a pivotal point, when the general design of the solar system was locked in. Jupiter, roughly 562 million miles from Earth today, has nearly 100 moons. But Batygin and his collaborator Fred Adams' research focused on two of the smaller ones, Amalthea and Thebe. Both are inside the orbit of the much larger moon Io, the most volcanically active world in the solar system, according to NASA. These smaller moons have curiously tilted orbits, and their paths around the planet seem to hold clues about how Jupiter and its bevy of moons moved in the past, Batygin told Mashable. As Io migrates away from Jupiter, its gravity causes a kickback — sort of like how a gun recoils when it's fired — that has contributed to the tilts of the smaller moons. "Similar to how our moon gradually moves away from Earth due to tides, Io is slowly drifting outward from Jupiter," Batygin said. By measuring Amalthea and Thebe's tilted orbits, the scientists reconstructed Io's previous position. That location, they said, should help determine the outer edge of the disk of gas and dust that once surrounded the planet. Based on where they believe the disk ended, the researchers extrapolated how fast Jupiter was spinning back then: about once per day, comparable to its spin now. Knowing Jupiter's early spin also helped them calculate its size. By applying the physics rules of spinning objects, they figured out how big Jupiter had to have been to match that rotation. The size of a young planet sheds light on its heat and interior dynamics as well. The scientists have concluded that early Jupiter must have started out extremely hot — about 2,000 degrees Fahrenheit. That's a far cry from its modern average temperature of about -170 degrees. The heat suggests Jupiter had a much stronger magnetic field. That allowed the team to calculate how fast Jupiter was collecting gas and growing — about the weight of one modern-day Jupiter every million years. "It's astonishing," said Adams in a statement, "that even after 4.5 billion years, enough clues remain to let us reconstruct Jupiter's physical state at the dawn of its existence."
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6 days ago
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Scientists Find Jupiter Used to Be More Than Twice Its Current Size
You don't need us to tell you that Jupiter, which has more than twice the mass of all the other planets in the Solar System combined, is the biggest game in town (other than the Sun, at least.) But believe it or not, it may have once been even bigger. Try more than double its current size, according to new research from Caltech and the University of Michigan — boasting enough volume to fit 2,000 Earths inside it with room to spare. Over time, the bloated world cooled off, contracting to the relatively humbler size it is today. The findings, published in a new study in the journal Nature Astronomy, provide a window into the Solar System's early evolution, around 3.8 million years after the first solids formed. Jupiter, with its enormous gravitational pull — and as the first planet to form — would have played an instrumental role in determining how the orbits of the nascent planets eventually settled. "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," co-lead author Konstantin Batygin, a professor of planetary science at Caltech, said in a statement about the work. "This brings us closer to understanding how not only Jupiter but the entire Solar System took shape." The clues to uncovering this early episode of Jupiter's past lie in two of its small moons, Amalthea and Thebe, which exhibit unusual orbits that aren't fully explained by their host's current size. To examine this discrepancy, the researchers bypassed existing planetary formation models and focused on aspects of the Jovian system that could be directly measured, including the orbital dynamics of the tiny moons and the planet's angular momentum. Their calculations revealed that, around 4.5 billion years ago, Jupiter must have had a radius up to 2.5 times greater than it is today. Likewise, its magnetic field — terrifyingly, as it's already 20,000 stronger than the Earth's — would have been a staggering 50 times more powerful. This dramatically shapes our idea of Jupiter in a critical moment in the Solar System's evolution, when the great disk of matter surrounding the Sun called the protoplanetary disk, which gave birth to the planets, evaporated. Mind-boggling as they are, these findings, the researchers say, are consistent with the prevailing core-accretion theory describing how giant planets formed. According to this theory, the giant planets began as heavy, solid cores floating on the farther and colder side of the protoplanetary disk, pulling in the lighter gas molecules surrounding them — first gradually, and then after passing a threshold of mass, much more rapidly. The exact details surrounding the planets' origins are still hotly contested. But the researchers say they've made the most precise measurements to date of primordial Jupiter's size, spin rate, and magnetic conditions, which will be indispensable to furthering our understanding of the Solar System's architecture. "What we've established here is a valuable benchmark," Batygin said. "A point from which we can more confidently reconstruct the evolution of our Solar System." More on astronomy: Astronomers Baffled by a Suspicious, Perfectly Round Sphere in Our Galaxy
