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The mysterious evolution of the solar system: Why did the planets migrate to their current orbits?
Recently, scientists have launched in-depth research on the evolution of the solar system, one of the most influential theories is the "Nice Model". This model not only explains the migration process of the planets, but also provides explanations for many astronomical phenomena, such as late heavy bombing events and the formation of the Oort cloud.
The Nice model presents a scenario regarding the dynamical evolution of the solar system, focusing on the migration of giant planets (such as Jupiter, Saturn, Uranus, and Neptune) from their originally compact configuration to their current position, a process that occurs when the original proto-dial disk dissipates after.
According to the Nice model, the initial four giant planets orbited in near-circular orbits about 5.5 to 17 AU from the Sun, quite close to each other compared to today. Over time, the gravitational interactions between these planets and the perturbation of small ice rocks gradually changed their orbits, eventually forming the cycles we observe today.
The core of the Nice model can be traced back to several papers published in the journal Nature in 2005, which were jointly completed by an international group of scientists. Models suggest that as small ice rocks gradually approach under the gravitational pull of the giant planet, Jupiter’s large gravitational backhaul leads to migration and expansion of the remaining planets, a process that eventually allows the planet to reach a more stable orbit.
A very small amount of momentum exchange will eventually cause significant changes in planetary orbits throughout the solar system, with millions of years of gradual migration allowing Jupiter and Saturn to cross a 1:2 resonance, each exacerbating itself under each other's gravitational pull eccentricity and triggered dynamic instability on other planets.
As the planets changed, the original planetary disk also suffered a massive disturbance, and almost all small ice rocks were thrown out of the solar system, which explains why we find almost no high-density objects in the outer solar system region. This phenomenon is one of the key factors that the Nice model can successfully explain.
The Late Heavy Bombing Event (LHB) is an important prediction of the Nice model, which argues that planetary migration events caused a surge in collisions between celestial bodies, resulting in a brief but intense bombing period. However, combined with recent research, the existence of LHB is inconsistent with some observational data, which has also triggered widespread discussion and reflection in the scientific community.
With further observations and calculations, scientists have come to realize that it remains a challenge to seek other alternative models to understand the formation of the early solar system if the properties of some asteroids cannot be explained by the Nice model.
“Although the Nice model has its advantages for describing the dynamics of objects similar to Neptune and Jupiter in specific regions, this model is struggling to explain some of the observed features and still needs further adjustments and enhancements.”
In addition, the Nice model also proposes an explanation for the formation of satellite systems on outer planets, arguing that these bodies are able to be acquired by interplanetary mutual gravitational behavior. The most famous example is Neptune's largest moon, Triton, which scientists speculate may have been captured during the conversion of an asteroid into a binary galaxy in the early solar system.
Even, this model can explain why the various kinds of small objects we see today in the Kuiper Belt formed. However, the dynamic processes hidden behind all this still puzzle the scientific community, showing that there are still many unsolved mysteries in the evolution of the early solar system.
The researchers' efforts to compare simulated and actual observational data of this process are invigorating. These comparisons make our compensation clearer, gain a deeper understanding of the growth and evolution processes of early planets, and constantly challenge and overthrow old ideas.
At the moment, although the Nice model faces adjustments and challenges, it remains one of the important theories for exploring the evolution of the solar system. Its existence not only enriches human understanding of the universe, but also leaves us with countless spaces for discovery and thinking.
During this exploration, what factors prompted these planets to flip and change at will, like dice, to the architecture of the solar system we observe today?
