A frozen planet monster expelled from the solar system billions of years ago



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Not to say that Hoth really existed or that wampa and tauntaun are real, but in the first and violent days of our solar system, a monstrous frozen planet was launched – perhaps into a galaxy far, far away.

Whatever our version of Hoth was, it may have been the elusive ninth planet that some astronomers continue to search for. If it were indeed Planet 9, anyone looking to find it would be disappointed to find that it left the solar system centuries ago. New research has found that there was once a huge ice giant between Saturn and Uranus that was ejected by gravitational forces. The unusual arrangement of the planets in the solar system led a team of scientists to create simulations that inverted it to understand its formation, which is how the mysterious ice giant appeared.

“There are many things about the solar system that seem at odds with the types of systems detected by exoplanet detection surveys such as TESS and Kepler,” said Matt Clement, postdoctoral fellow at the Carnegie Institution for Science, who led a recently published study. up Icarus, he tells SYFY WIRE.

Our cosmic courtyard is weird (we just think it’s normal because we live here). Unlike many planetary systems that orbit Sun-like stars, there are no hot super-Earths around here. These are planets larger than Earth but smaller than Neptune. They don’t necessarily have to be rocky or habitable from a distance, but there is nothing in that size range in the solar system, even though super-Earths are common throughout the Milky Way. Hot super-Earths orbit about half as many Sun-like stars. Their heat comes from orbiting so close to their stars, so why are the planets closest to our star so small in comparison?

Clemente believes that Jupiter devoured so much gas and dust during its formation, it became large enough to have an immense amount of gravity that prevented the material from heading to planets closer to the Sun. They struggled to grow in its shadow.

“The inner solar system must have been starved enough of the mass and material that forms the planet relatively soon after the birth of the Sun,” he said. “One possible reason for this is that Jupiter has been growing so fast, its gravitational perturbations have prevented the material from making its way to the growth of Venus, Earth and Mars. Therefore, terrestrial planets such as Earth have grown from the remaining crumbs of the rapid formation of Jupiter. “

It is not only the innermost planets that do not adapt to what has been observed in other star systems. Another strange thing about the part of space we live in is that the larger planets hiding further back are different from the giant exoplanets in most other systems. Exoplanets similar to Jupiter and Saturn in mass and distance from their star have much less circular orbits and more distant from each other. Other star systems are thought to form with planets much closer to each other in resonant orbits, where one planet will orbit its star X times for every Y times another planet orbits it. The fact is that the planets in these arrangements are prone to chaos if one of them is ejected from the system.

“These types of systems experience violent orbital instabilities in which planets are lost and ejected, and the remaining ones move rapidly and reach the elliptical orbits and widely spaced orbital structures we observe,” said Clement.

The way the solar system evolved to become the mismatched star system now gets even stranger if you go back several billion years. The giant planets are thought to have formed and orbited close to each other just as they tend to do in many other systems, and there may have been at least one other ice giant until gravitational instability. sent to fly into space. Clement and his team saw this in action after running over 6,000 computer simulations that essentially destroyed the solar system and rebuilt it. Some previous simulations had shown that Uranus or Neptune were being ejected with Saturn being kicked in the back. Others showed only mild instabilities that weren’t strong enough to hurl a planet into space.

The new simulations conducted by Clement’s team reveal something different. If Jupiter and Saturn originally formed farther apart from each other and were positioned so that Jupiter completed two orbits for each orbit of Saturn, both planets would have interacted with the gas that shaped their orbits in the more elliptical paths that follow today. This is still hypothetical as there are so many possibilities for what could have happened. Researchers had to run simulation after simulation to see what fit and where as best they could.

“We first simulated how the giant planets grew and organized themselves into compact, resonant chains of orbits,” said Clement. “So we ran thousands of computer simulations of these chains to study all the different possibilities of instability. Finally, we compared important aspects about the final structures of these systems with the real architecture of the solar system to see which “birth configurations” of the giant planets seemed most likely. “

As long as the Sun remains alive, Clement believes the orbits will remain fairly stable, although there is a chance that Mercury could end up crashing into Venus and being ejected in the distant future. At least it doesn’t seem like there will be any great planet games in our solar system anytime soon.

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