It is known that gas giants around other stars are often very close to their sun. According to accepted theory, these gas planets were formed far away and then migrated to an orbit closer to the star.
Now, researchers from Lund University and other institutions have used advanced computer simulations to learn more about Jupiter's journey through our own solar system about 4.5 billion years ago. At that time, Jupiter was formed quite recently, as did the other planets in the solar system. The planets were gradually built by cosmic dust, which circled around our young sun on a disk of gas and particles. Jupiter was no bigger than our own planet.
The results show that Jupiter was formed four times longer from the sun than the current position would indicate.
"This is the first time we have evidence that Jupiter was forming a long way from the sun and then migrated to its current orbit. We found evidence of the migration in the Trojan asteroids that revolve near Jupiter," explains Simona Pirani, a graduate student in astronomy at Lund University and leading author of the study. [1
"Asymmetry has always been a mystery in the solar system," says Anders Johansen, professor of astronomy at Lund University.
The research group had previously been unable to explain why the two asteroid groups do not contain the same number of asteroids. But Simona Pirani and Anders Johansen have, together with other colleagues, now identified the cause by recreating the events in Jupiter's formation and how the planet gradually withdrew into its Trojan asteroids.
Thanks to extensive computer simulations, the researchers have estimated that current asymmetry could only occur if Jupiter was formed four times longer in the solar system and then migrated to its current position. During his journey to the sun, Jupiter's own gravity took on more trojans in front of it than behind it.
According to the calculations, Jupiter's migration continued for about 700,000 years, for a period of about 2-3 million years after the celestial body began its life as an ice-steroid far from the sun. The journey into the solar system followed a spiral path where Jupiter continued to circle around the sun, albeit in an increasingly narrow path. The cause of the actual migration refers to the forces of gravity from the surrounding gases in the solar system.
The simulations show that the Trojan asteroids were withdrawn when Jupiter was a young planet without a gas atmosphere, which means that these asteroids probably consist of building blocks similar to those that formed the Jupiter core. In 2021, NASA's space probe Lucy will be launched in orbit around six of Jupiter's Trojan asteroids to study them.
"We can learn a lot about Jupiter's core and formation from studying the Trojans," says Anders Johansen.
The authors of the study also suggest that the gas giant Saturn and the icebergs Uranus and Neptune would have similarly migrated.
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