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We have An idea of what the solar system’s past was like: it was violent and chaotic. However, we are still studying how violent it is. Current models suggest that at some point after their formation, the giant planets went through a period of such extreme instability that one or even two Earth-sized objects Uranus or Neptune They were expelled into interstellar space. If this scenario occurs, we might find evidence in the most unexpected places in the solar system, such as Earth’s moons Gobitr especially those found in Uranus.
An article recently published in Icarus He analyzed 122 possible scenarios of this instability to evaluate how satellite systems would react to planets “left behind.” The researchers concluded that it would be very difficult to explain the current properties of Uranus’ moons without some violent instabilities occurring. This type of instability only appears in models that contain more giant planets than we see today.
Most likely, the authors suggest, Uranus’ moons have been destabilized at least twice in the past: first by an impact that tilted the planet, and then by close encounters between the giant planets during the destabilization. That chaos, fueled by the presence of one or more planets that were subsequently ejected, would have destroyed and rebuilt the moon system into what we see today.
The solar system and chaos
Jupiter, Saturn, Uranus, and Neptune did not always have their current positions in the solar system. According to the planetary instability model, they were born slightly closer to the Sun and closer together. After millions of years, they migrated towards their current orbits.
But there are details of this model that do not fit the observations. For one thing, the current orbits of Jupiter and Saturn are eccentric, while there are specific structures like the Kuiper Belt that look like they should have prevented Neptune from moving to its current position. In simulations, the planets did not arrive where they are today.
It is therefore possible that the solar system at one time contained a larger number of planets, and these were the ones that “pushed the others out.” Under this hypothesis, the puzzle of the solar system fits better. The problem is that those bodies, if they existed, are gone. They were exhumed and left no traces or physical fragments. This leaves the idea of missing planets in the realm of hypotheses, waiting for sufficient evidence to accumulate to confirm it.
Extraordinary moon
New Icarus The study tested the missing planets hypothesis using Uranus’ moons as direct evidence. A total of 122 simulations of the evolution of the solar system were used. In 85% of the scenarios, the Uranus satellite system collapsed. Its moons could only survive in a handful of scenarios, and in each of them, the lost and ejected planets hypothesis was a perfect fit.
The report refers to Miranda, the smallest moon in the main Uranus system. Astronomers consider it the most unusual in the solar system. It is incomplete, as if stitched together from scraps, is very icy for its size, and very small compared to the rest of Uranus’ moons. It is also geologically active.
Astronomers believe that Miranda is the debris of a larger object. The study reinforces this idea and suggests that it is the clearest example of the effects of planetary instability.
