Our solar system. Astronomers have been dealing with this for a long time. But they still haven’t unlocked all of its mysteries. You have therefore always wondered how the giant planets Jupiter, Saturn, Uranus and Neptune got into the orbits as we know them today. A question to which a team from Michigan State University (USA) is now providing an answer. Who could even confirm the existence of a fifth giant – the famous Planet X – the ninth planet in our solar system, some 80 billion kilometers from our star.
As a starting point for her work: a survey on the so-called Nice model – because it was developed at the observatory of the Côte d’Azur. He would like the giant planets to have taken a “compact” position before migrating to the ones they occupy today. All under the influence of an instability that occurred long after the disk of protoplanetary gas broke up. Michigan State University researchers have tried to imagine a different scenario. That of planets moving by “rebound effect” even as the disk evaporates.
“All planetary systems form a disk of gas and dust. It’s a natural byproduct of star formation, astronomer Seth Jacobson said in a statement. But when a star ignites and starts burning its nuclear fuel, it emits light and heats up this disc, which it eventually blows from the inside to the outside of the system.”
A “very universal” instability
Astronomers from Michigan State University have found that this process created a veritable hole in the cloud of gas and dust left over from the formation of our sun. A hole that has grown and is gradually catching up with the primitive orbits of giant planets. This leads to the instability created by the Nice model. But an instability that the simulations introduce here much earlier. “Less than 10 million years after the birth of the solar system,” the researchers estimate. And a lot faster too. With a mixture of materials between the inner solar system and the outer solar system.
“This process has churned up our region of the solar system. Our earth grew from there,” says Seth Jacobson. Our planet’s geochemistry also appears to be trying to confirm the mix conjured up by Michigan State University astronomers while our planet was in the process of formation. And the researchers now assume that this scenario could also apply to other planetary systems. Indeed, the manner in which the instability at the origin of the current structure of our solar system seems to have finally appeared turns out to be more “universal” than the Nice model envisaged.
A model consistent with the existence of a ninth planet
The description proposed by the Michigan State University researchers also sheds new light on the question of Planet X, that mysterious – and still hypothetical – ninth planet that would complete our solar system’s family portrait. Remember that according to the Nice model, there should be a fifth giant planet. But that it would have been ejected from our solar system during its instability, helping the other gas giants – those we know well – settle permanently in their respective orbits. The problem is that some astronomers believe there is still a giant planet hiding at the edge of our solar system. But they’re still struggling to find evidence.
The new model presented here does not provide a definitive answer. The researchers only note that their simulations yield similar results when they assume a system of four or five giant planets. A system that starts with four gas giants ends up with orbits that match very closely those of Jupiter, Saturn, Uranus, and Neptune. But a system that originally consisted of five gas giants seems most likely to ultimately end up with four giant planets. Let’s hope that the Vera Rubin Observatory – due to be up and running by the end of next year – will finally give us the answer!
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