Jupiter is shrinking and used to be twice as big, mind-boggling study reveals
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Jupiter is shrinking and used to be twice as big, mind-boggling study reveals
Jupiter’s radius used to be twice its current size, a new study says. The planet had a magnetic field 50 times more powerful than it is today. The findings could help scientists develop a clearer picture of the early solar system. The calculations don’t depend on how Jupiter formed, relying instead on directly observable quantities, the researchers say.”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,” study co-author Fred Adams said in a statement. “This brings us closer to understanding how not only Jupiter but the entire solar system took shape,” he added. “A point from which we can more confidently reconstruct the evolution of our solar system”
Jupiter, the solar system’s largest planet, used to be even bigger, according to a new study.
The cloud of gas and dust from which the sun and planets formed dissipated around 4.5 billion years ago. At that time, Jupiter was at least twice its current size, and its magnetic field was about 50 times stronger, researchers found. The findings, which the team described in a study published May 20 in the journal Nature Astronomy , could help scientists develop a clearer picture of the early solar system.
“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,” study co-author Konstantin Batygin , a planetary scientist at Caltech, said in a statement . “This brings us closer to understanding how not only Jupiter but the entire solar system took shape.”
Jupiter’s immense gravity — along with the sun’s — helped fashion the solar system, shaping the orbits of other planets and rocky bodies. But how the giant planet itself formed remains opaque.
To gain a better picture of Jupiter’s early days, the researchers studied the present-day, slightly tilted orbits of two of Jupiter’s moons , Amalthea and Thebe. The paths these moons chart are similar to what they were when they first formed, but the moons have been pulled slightly over time by their larger, volcanically active neighbor Io . By analyzing the discrepancies between the actual changes and those expected from Io’s nudges, the researchers could work out Jupiter’s original size.
Related: ‘This has left us scratching our heads’: Astronomers stumped by James Webb telescope’s latest views of Jupiter
When the solar nebula dissipated, marking the end of planet formation, Jupiter’s radius would have been between two and 2.5 times its current size to give Amalthea and Thebe their current orbits, the scientists calculated. Over time, the planet has shrunk to its current size as its surface cools. Then, the team used the radius to calculate the strength of the planet’s magnetic field , which would have been around 21 milliteslas — about 50 times stronger than its current value and 400 times stronger than Earth’s.
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“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,” study co-author Fred Adams , an astrophysicist at the University of Michigan, said in the statement.
The findings sharpen researchers’ view of the solar system at a critical transition point in its history. The calculations also don’t depend on how Jupiter formed — a process that’s still not understood in detail — relying instead on directly observable quantities.
“What we’ve established here is a valuable benchmark,” Batygin said in the statement. “A point from which we can more confidently reconstruct the evolution of our solar system.”
Jupiter Was Twice Its Current Ginormous Size, Scientists Discover
Astronomers from Caltech and the University of Michigan have reconstructed the early evolution of Jupiter. Just 3.8 million years after the first solids emerged, Jupiter’s volume was at least twice its current volume. This rapid growth phase developed the planet and put it on the path to becoming the Jupiter we see today. Jupiter continues to shrink to this day as its surface and internal temperatures fall, compressing and heating its core and thus losing energy. It would need to be at least 85 times its current mass to be able to ignite hydrogen fusion, a defining feature of all stars. It is thought to have played a vital part in the stabilizing the planets so that life could emerge on Earth on the planet’s surface. The research has been published in the journal Astronomy and Astrophysics, by Konstantin Batygin and Fred Adams, and published in Nature. The team’s work gives us a new tool for understanding Jupiter and its role in the Solar System.
Prepare, then, to have your mind blown – the Solar System’s biggest planet was once even bigger. New calculations suggest that early Jupiter could have had as much as 2.5 times its volume today, say astronomers Konstantin Batygin from Caltech and Fred Adams of the University of Michigan.
Based on their study of two of the moons of Jupiter, the scientists have found that, just 3.8 million years after the first solid materials formed in the Solar System, Jupiter was 2 to 2.5 times its current volume, with a significantly more powerful magnetic field to boot.
This is a finding that supports the bottom-up method of planet formation for the giant gas-shrouded world.
“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,” Batygin says. “This brings us closer to understanding how not only Jupiter but the entire Solar System took shape.”
We believe that rocky worlds, like Mercury, Venus, Earth, and Mars, form from the bottom up, a gradual accumulation of dust and rocks to eventually build an entire world, with a differentiated core and all. This is known as core accretion.
Gas giants are thought to start out the same way, but once they reach a certain mass, around 10 times the mass of Earth, they have enough gravity to retain a substantial gas envelope, and begin to accumulate that, too. This process is thought to have taken place in the outer Solar System, since there wouldn’t be enough material closer to the Sun to accumulate the large core.
Since the formation and evolution of Jupiter is thought to have played a key role in the formation and evolution of the architecture of the Solar System, the details of how it was born and how it grew are of intense interest to planetary scientists. Since we can’t just, you know, rewind the Solar System though, we need to look at what’s happening now to try and reconstruct the past.
Typically, this involves using standard models of planet formation collected from observing planetary systems (including our own) throughout the Milky Way and constructing a model based on those observations. These models, however, involve a lot of guesswork and connecting the dots, and as such, tend to leave significant uncertainties.
Batygin and Adams took a different approach: they studied the orbital motions of Amalthea and Thebe, two tiny Jovian moons that orbit close to the planet, closer even than the orbit of Io. The orbits of these tiny moons are tilted with respect to Jupiter’s equator.
These tilts, previous work has shown, can be used to back-trace the orbital history of these tiny moons. Batygin and Adams used that orbital history to reconstruct the early evolution of Jupiter.
“It’s astonishing that even after 4.5 billion years,” Adams says, “enough clues remain to let us reconstruct Jupiter’s physical state at the dawn of its existence.”
Their results showed that Jupiter had a period of rapid, intense growth early in the history of the Solar System. Just 3.8 million years after the first solids emerged, Jupiter’s volume was at least twice its current volume.
Moreover, its magnetic field was 50 times higher than it is now, facilitating a rate of accretion from a disk of material feeding into the planet of around 1.2 to 2.4 Jupiter masses per million years. This rapid growth phase developed the planet and put it on the path to becoming the Jupiter we see today.
When the material around Jupiter eventually dissipated, the planet itself contracted under its own gravity, reducing its volume, and increasing its spin speed. Jupiter continues to shrink to this day as its surface and internal temperatures fall, compressing and heating its core and thus losing energy, although this occurs at a very slow rate.
Even with a larger volume, Jupiter was never close to massive enough to achieve star status. It would need to be at least 85 times its current mass to be able to ignite core hydrogen fusion, a defining feature of all stars.
What the team’s work gives us is a new tool for understanding Jupiter and its role in the Solar System, where it is thought to have played a vital part in stabilizing the planets enough so that life could emerge on Earth.
“What we’ve established here is a valuable benchmark,” Batygin says. “A point from which we can more confidently reconstruct the evolution of our Solar System.”
The research has been published in Nature Astronomy.
Source: https://www.livescience.com/space/jupiter/jupiter-is-shrinking-and-used-to-be-twice-as-big-mind-boggling-study-reveals