The solar system acquired its current configuration shortly after its formation

Hello reader! My name is Irina, I’m conducting a telegram channel about astrophysics and quantum mechanics “Quant” . This time I prepared for you a translation of an article on the process of configuring the Solar System to the state that we are observing now (and most importantly, when it happened!)
Enjoy reading.



A model developed by Brazilian researchers shows a chaotic phase that places objects in current orbits.

The hypothesis that the solar system arose from a giant cloud of gas and dust was first put forward in the second half of the 18th century by the German philosopher Immanuel Kant and further developed by the French mathematician Pierre-Simon de Laplace. Currently, astronomers are unanimous in this matter.

But it was not without controversy. Until recently, it was believed that the solar system acquired its present features as a result of a period of turbulence that occurred approximately 700 million years after its formation. However, some of the latest studies show that it formed in the more distant past, at some stage during the first 100 million years.

A study by three Brazilian researchers provides strong evidence for this earlier structuring. According to an article published in the journal Icarus, the study was supported by the São Paulo Research Foundation - FAPESP. All authors are affiliated with the São Paulo State University Polytechnic School in Guaratingueta (Brazil).

Lead author is Rafael Ribeiro de Souza. The other two authors are Andre Isidoro Ferreira Da Costa and Ernesto Vieira Neto, lead researcher for this study.

“A large amount of data obtained as a result of detailed observation of the solar system allows us to accurately determine the trajectories of many bodies orbiting the sun,” said Ribeiro. - This orbital structure allows us to write the history of the formation of the solar system. Leaving the gas-dust cloud surrounding the Sun about 4.6 billion years ago, giant planets formed in orbits located closer to each other, as well as closer to the Sun. The orbits were also more coplanar and more circular than now, and more interconnected in resonant dynamical systems. "These stable systems are the most likely result of the gravitational dynamics of the formation of planets from gaseous protoplanetary disks."

“The four giant planets — Jupiter, Saturn, Uranus and Neptune — emerged from the gas-dust cloud in more compact orbits,” continues Isidoro. “Their movements were very synchronized due to the resonant circuits, with Jupiter making three orbits around the Sun, and Saturn two. All the planets were involved in this synchronism, generated by the dynamics of the primary gas disk and the gravitational dynamics of the planets. ”

However, throughout the entire area of ​​the formation of the outer solar system, including the zone located outside the current orbits of Uranus and Neptune, the solar system had a large number of planetesimals, small bodies of stone and ice were considered building blocks of planets and the forerunners of asteroids, comets and satellites.

The outer planetesimal disk began to upset the gravitational equilibrium of the system. Resonances were broken after the gas phase, and the system entered a period of chaos in which giant planets interacted violently and threw matter into space.

“Pluto and its icy neighbors were pushed into the Kuiper belt, where they are now, and the entire group of planets migrated to orbits farther from the Sun,” Ribeiro said.

The Kuiper Belt, the existence of which was proposed in 1951 by the Dutch astronomer Gerard Kuiper and later confirmed by astronomical observations, is a toroidal structure consisting of thousands of small bodies orbiting the Sun.

The diversity of their orbits is not observed in any other part of the solar system. The inner edge of the Kuiper belt begins in the orbit of Neptune about 30 astronomical units from the Sun. The outer edge is approximately 50 astronomical units from the sun. One A.E. equal to the distance from the earth to the sun.

Returning to the violation of synchronism and the onset of the chaotic stage, the question arises, when did this happen - very early in the life of the solar system, when it was 100 million years old or less, or much later, probably about 700 million years after the formation of the planets?

“Until recently, the hypothesis of late instability prevailed,” Ribeiro said. —The dating of moonstones brought by Apollo astronauts suggests that they were created by asteroids and comets that crashed into the lunar surface at the same time. This cataclysm is known as the "late heavy bombardment" of the moon. If this happened on the moon, then it probably also happened on Earth and other planets of the solar system. Since a large amount of matter in the form of asteroids and comets was projected in all directions in the solar system during a period of planetary instability, it was inferred from the lunar rocks that this chaotic period was late, but in recent years the idea of ​​a “late bombardment” of the moon has gone out of fashion. ”

According to Ribeiro, if a late chaotic catastrophe occurred, it would destroy the Earth and other near-Earth planets, or at least cause disturbances that would place them in completely different orbits than those we are observing now.

In addition, it was discovered that the moonstones brought by the Apollo astronauts were fired at one stroke. If they arose at the end of the instability of giant planets, then there would be evidence of several collisions, given the scattering of planetesimals by giant planets.

“The starting point for our study was the idea that instability should be dated dynamically. Instability could occur later if there was a relatively large distance between the inner edge of the planetesimals disk and the orbit of Neptune when the gas was exhausted. This relatively large distance was unacceptable in our simulation, ”Ribeiro said.

This argument is based on a simple assumption: the smaller the distance between Neptune and the planetesimal disk, the stronger the gravitational effect, and therefore, the earlier the period of instability. Conversely, later instability requires greater distance.

“We first created a model of the primary planetesimal disc. To do this, we had to return to the formation of the ice giants Uranus and Neptune. Computer simulations based on a model constructed by Professor Isidoro [Ferreira Da Costa] in 2015 showed that the formation of Uranus and Neptune may have occurred in planetary nuclei with several Earth masses. The massive collisions of these SuperEarths explain, for example, why Uranus rotates on its side, ”Ribeiro said, referring to the“ tilt ”of Uranus, with the North and South poles located on the sides, and not above and below.

Previous studies pointed to the importance of the distance between Neptune’s orbit and the inner boundary of the planetesimal disk, but they used a model in which four giant planets were already formed.

“The novelty of this latest study is that the model does not start with fully formed planets. Instead, Uranus and Neptune are still in a growth stage, and two or three collisions with objects weighing up to five earth masses are the driving force behind growth, ”said Isidoro.

“Imagine a situation in which Jupiter and Saturn are formed, but instead of Uranus and Neptune, we have five to ten SuperEarths. The super-earths are forced by gas to synchronize with Jupiter and Saturn, but since there are many of them, their synchronism fluctuates, and they eventually collide. Collisions reduce their number, making synchronization possible. In the end, Uranus and Neptune remained. While two ice giants formed in the gas, the planetesimal disk was absorbed. Part of the matter was accreted to Uranus and Neptune, and part was transferred to the outskirts of the Solar system. Thus, the growth of Uranus and Neptune determined the position of the inner boundary of the planetesimal disk. What is left of the disc is now called the Kuiper belt. The Kuiper Belt is basically a relic of the original planetesimal disc,which was once much more massive. ”

The proposed model is consistent with the current orbits of the giant planets and the structure observed in the Kuiper belt. This is also consistent with the movement of the Trojans, a large group of asteroids that share the orbit of Jupiter and, apparently, were captured during the synchronization violation.

According to an article published by Isidoro in 2017, Jupiter and Saturn were still in the formative stage, and their growth contributed to the displacement of the asteroid belt. The last article is a kind of continuation, starting from the stage at which Jupiter and Saturn were fully formed, but still synchronized, and describes the evolution of the solar system from this point on.

“The gravitational interaction between the giant planets and the planetesimal disk caused disturbances in the gas disk, which propagated in the form of waves. Waves created compact and synchronous planetary systems. When the gas ended, the interaction between the planets and the planetesimal disk disrupted synchronism and generated a chaotic phase. Taking all this into account, we found that there simply are no conditions for the distance between the orbit of Neptune and the inner boundary of the planetesimal disk to become large enough to support the hypothesis of late instability. This is the main contribution of our study, which shows that instability occurred in the first 100 million years and may have occurred, for example, before the formation of the Earth and the Moon, ”Ribeiro said.