Home Sciences A new cosmological model suggests that the ninth planet may exist

A new cosmological model suggests that the ninth planet may exist


A new cosmological model suggests that Planet X may exist due to the instability of the early solar system, which dislocated the orbits of Jupiter, Saturn, Uranus and Neptune and banished the fifth giant 80,000 million kilometers from our star.

A new cosmological model explains the current position of the four giant planets in our solar system, Jupiter, Saturn, Uranus and Neptune, and suggests that the Planet Xwhich is believed to be in the most remote part of our solar system.

Planet X is a totally hypothetical planet that would be hidden about 80,000 million kilometers from our Sun, well beyond the orbit of Neptune, which has been tracked from the 19th century to the present day.

Also called “Planet Nine,” it could have a mass 10 times that of Earth and orbit about 20 times farther from the Sun than Neptune. It can take between 10,000 and 20,000 Earth years to complete one orbit around the Sun.

The hypothesis of the existence of this ninth planet is based on the still unsolved mysteries of our solar system: astronomers do not understand how the four giant planets ended up in the orbits they have today.

What we know for sure is that our solar system has not always looked the way we see it today, because throughout its history, the orbits of the planets that make it up have changed radically.

early solar system

The process of formation of a solar system is also well known: stars are born from massive, swirling clouds of gas and cosmic dust.

Once our sun ignited, the early solar system was still filled with a primordial disk of gas that played an integral role in the formation and evolution of planets, including gas giants.

At the end of the last century, scientists began to think that the gas giants initially revolved around the sun in orderly, compact, evenly spaced orbits.

However, Jupiter, Saturn, and the other giants have long since settled into orbits that are relatively longer than they are wide (oblong), crooked, and stretched out. We have never known why.

nice model

In 2005, an international team of scientists proposed an answer to that question in three landmark papers published in Nature. The solution was originally developed in Nice, France, and is known as the nice model.

It posits that in our solar system there was at some point an instability between these giant planets, a chaotic set of gravitational interactions that finally placed them in their current orbits.

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Although the Nice Model remains a valid explanation, in the last 17 years, scientists have been asking new questions about what triggered the instability proposed by the Nice Model.

The gas giant’s instability was originally thought to have occurred hundreds of millions of years after the dispersal of that primordial gas disk that gave rise to the solar system.

But the most recent evidence, including some found in moon rocks recovered by the Apollo missions, suggests it happened much earlier. That also raises new questions about how the inner solar system that houses Earth evolved.

new research

New research, led by seth jacobsonfrom Michigan State University, proposes another alternative scenario to the Nice Model to explain the orbits of Jupiter, Saturn, Uranus and Neptune.

The new model suggests that the gas giants could have followed their current paths because of how the primordial gas disk evaporated, and that this dissipation, occurring from the inside out, provided a natural trigger for the solar system’s instability.

“All solar systems form in a disk of gas and dust. But as the sun lights up and begins to burn its nuclear fuel, it generates sunlight, heats the disk and eventually evaporates, ”explains Jacobson, summarizing what the model indicates of him.

This situation created a growing hole in the gas cloud, which was concentrated in the place occupied by the Sun, according to this research. As the hole grew, its edge cut through each of the gas giants’ orbits, disrupting their original trajectory.

system instability

This transition led to the orbital instability of the giant planets with a very high probability, according to the computer simulations developed in this research.

Furthermore, the process of shifting these large planets to their current orbits occurred much earlier than the Nice Model said: less than 10 million years after the birth of the solar system.

It happened when the Earth was still beginning to form and caused that cosmic vortex to produce a mixture of the outer solar system and with material from the inner solar system, according to this model.

It is this process that will shake the inner solar system and influence the formation of our planet, establishing an apparent link between the instability of the solar system and the formation of our planet.

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The authors of this research emphasize that this explanation can also be applied to other solar systems in our galaxy, where scientists have observed gas giants orbiting their stars in configurations similar to those we see in the Milky Way.

That would mean that the instability of our solar system is a universal and consistent process, and not a unique experience in the formation of the universe, according to Jacobson.

Planet X

It also sheds light on possible planet X, calling into question the number of planets that make up our solar system.

We currently know there are eight, but it turns out that the Nice Model works a little better if the early solar system is credited with five gas giants, instead of four.

According to this model, that extra planet was ejected from our solar system during the instability, helping known gas giants to position themselves in their current orbits.

In 2015, Caltech researchers obtained evidence that there may still be an undiscovered planet around the outskirts of the solar system, but its existence has yet to be proven.

More possibilities

The question that arises is whether the additional planet proposed by the Nice Model could be the supposed planet X suggested by the Caltech research, something to which the new research does not provide an answer.

However, he has gone a bit further than the Nice Model in his simulations: he obtained a similar result to explain the orbits of the four giants, whether or not they included an additional planet.

A system made up of four gas giants from the start ends up with orbits that match very well those of Jupiter, Saturn, Uranus and Neptune. But a system initially made up of five gas giants is more likely to reflect the orbits of all four giants, according to the new research.

This result is also not conclusive, but the researchers point out that we may soon have an answer: the Vera Rubin Observatorywhich will be able to image the entirety of its available sky every few nights due to its wide field of view, should detect Planet 9 if it’s really out there, once the observatory is operational in late 2023.


Early Solar System instability triggered by dispersal of the gaseous disk. Beibei Liu et al. Nature, Volume 604, pages 643–646 (2022).

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