Our Solar system is the scene of the crime by the age of 4.6 billion years. Cratered surface, shifted the orbits of the planets and streams of interplanetary debris is the cosmic equivalent of blood stains, rasplakalsya on the wall and tire tracks fleeing with a squeal machine. These and other clues tell you about the chaotic early days of our planetary family. These clues are buried and our lost brothers, including the ninth planet (no, not Pluto), which beat out gravity shake-up that has undergone our Solar system in his youth.
Today the outer Solar system was divided between four giant worlds: Jupiter, Saturn, Uranus and Neptune. Behind them lies the Kuiper belt, an icy field of debris that wormed and Pluto.
“We must not delude ourselves into thinking that the outer part of the Solar system always been like this,” says David Nesvorny, a planetary scientist southwest research Institute in boulder, Colorado, who first spoke about the planet-the fugitive in 2011.
Where is the ninth planet?
Nesvorny is one of those scientists who are trying to figure out how the Solar system evolved in its first few hundred million years. Using sophisticated computer models, the scientists came to the story in which the young planets were formed relatively closely and then exchanged provisions, periodically bending down and jumping from one orbit to another. These simulations explain many little details about how planets, asteroids and comets revolve around the sun today.
Except there’s one problem. The story usually ends up being a Uranus or Neptune out of the Solar system, wrote Nesvorny in September, in Annual Review of Astronomy and Astrophysics.
As Uranus and Neptune remained in their places the spacecraft in the end, visited both planets — this narrative is not very foldable. But a fifth giant planet, as many believe, could be our missing hero of this tale and an important player in the history of our Solar system.
Phantom planet
To recreate the scene of ancient times, astronomers turn to computer models to generate thousands of different solar systems, collected in thousands of different ways. The lines of code they explain the laws of physics and the starting lineup of any of the planets, you can imagine. Scientists set the stage: a planet here, a few asteroids here, then leave and let nature do its thing. Few weeks in the real world millions of years in the simulation — astronomers finally dare to look and see how it feels newborn solar system. The closer to reality the better.
This Nesvorny did in 2009. He played with the virtual solar systems, trying to find the best way to save virtual virtual Uranus and Neptune from unilateral virtual tour in deep space.
The problem was Jupiter. This giant planet — Buster, the gravity of which may reach far beyond and expand, pushing small worlds and pulling the wreckage. In the most successful models of Jupiter and one of the two outer planets the rebound bounced away from each other, and finally settled on their current orbits. But it happened only in 1% of cases. In other 99% cases, Jupiter knocked Uranus or Neptune so much that they left the Solar system and never return.
“This is weird, because we know that Uranus and Neptune have survived,” says Nesvorny. So he continued to build the new system. After years of countless attempts of different scenarios, he began to add a sacrificial planet: the other planets that were destroyed to save others.
“I would run these simulations to see what would happen not taking them too seriously,” says Nesvorny. “But then I realized that there might be some truth”. He spent about 10 000 simulations, varying the number of additional planets, their initial locations and the masses in each case.
Best-case scenario — which expresses the Solar system most similar to the real — included an additional planet, which was located between the orbits of Saturn and Uranus. This world has been around just about as massive as Uranus and Neptune, or 16 times more massive than Earth. This planet could be confused with the orbit of Jupiter and be ejected from the Solar system.
But the chances are still small. Repeated simulation of such installation was achieved only in 5% of cases. “The present Solar system is neither a typical nor expected result,” wrote Nesvorny work in 2012 studying this idea, in collaboration with colleagues Alessandro Morbidelli from the Observatory of the Cote d’azur of France. But it was a significant improvement compared to 1% of the level of success of the simulations that included only the four giant planets, which we know and love today.
“Talking about the existence of a fifth giant planet is actually a lot easier than not talking,” said Sean Raymond, a planetary scientist from the University of Bordeaux in France. Although the evidence is largely circumstantial, “to have another one in those days would have been much more sense.”
It may seem that this is far-fetched. As astronomers might know something about what is happening more than 4 billion years ago? How can they know something about the planets that remain at the moment, not to mention those who are no more? It turns out that the planets leave behind battle scars, which planetary detectives can try to read.
Interplanetary blood stains
“We are certain that the planets were formed, not where they are now,” says Nathan Kaib, a planetary scientist at the University of Oklahoma in Norman.
This confidence appeared not so long ago. For most of the history of star observers assumed that the planets always moved in those orbits that have. But in the early 1990s, scientists realized that in this scenario, something is missed.
Immediately beyond the orbit of Neptune lies the Kuiper belt, a scattering of icy debris surrounding the Sun. “This is the blood stains on the wall,” says Konstantin Batygin, a planetary scientist at Caltech.
Location of Kuiper belt objects has led scientists to the inevitable conclusion: Neptune had to form closer to the Sun than it is now. Many of the Kuiper belt objects nailed together in concentric orbits, vaguely reminiscent of the striations on the plates. And this is not some random orbits — they are all closely tied to the orbit of Neptune.
Take Pluto, the most famous resident of the Kuiper belt. He and several hundred of his famous companions evade the Sun exactly two times for every three bypass by Neptune. Other threads of objects of the Kuiper bypassed once for every two rotations of Neptune, or four times for every seven.
The Kuiper belt is in no way could be in this movement alone. If, however, the Neptune, formed closer to the Sun, and then came out, its gravity were to work as a network, capturing the nearby interplanetary debris on these special orbits and launching them to move in a certain way.
This corresponds to some simulations that were conducted ten years ago. The formation of planets was terrible bloodshed, in which throughout the Solar system were scattered debris. Any fragments that came too close to Neptune, had to be attracted by the gravity of the planet. Since every action has an equal and opposite reaction, every time Neptune was drawn to a fragment, the planet is repelled in the opposite movement of the fragment direction. Over time, the Neptune slowly crawled away from the Sun.
Migration of Neptune influenced the other giant planets. In the end, Jupiter, Saturn and Uranus plowed the same field of debris and had to deal with similar gravitatsionnye interactions. If Neptune moved, all of these giant planets would be moved.
And it was clearly not a trip with the breeze.
Continuous fragmentation of all these fragments had to sculpt the orbits of the giant planets aligned in perfect circles, like clay on a Potter’s wheel is smoothed by the strong hand of the Potter. But atk did not happen. Planet of giants instead move in orbits which are slightly elongated and distorted. If someone crashed into the circle, spoiling the rounded pots.
Jumping Jupiter
In 2005, scientists found the culprit. The new model showed that at some point the giant planets had to endure the so-called “dynamic instability”. In other words, everything is upside down in a million years. The most probable source of this confusion was supposed to be a series of close passes between Saturn and either Uranus or Neptune — that is, the ice giants — koora sent one of these worlds in the direction of Jupiter. As you get closer to the giant planet, an ice giant’s gravitational influence on Jupiter, slowing it down and pushing into low orbit. But Jupiter is also strongly attracted to the approaching planet. An ice giant, being much easier, accelerated the slowdown of Jupiter away from the Sun.
This fight was for the Solar system gravitational mixer. Jupiter jumped inside, and the other outer planets popped out. This impact distorted the orbits of the giant planets and made them the way they are now. He also saved the inner Solar system — mercury, Venus, Earth, Mars and the asteroid belt — from mixing due to the long gravitational effects of Jupiter and Saturn. This problem also occurred in earlier simulations.
This brings us to the removal of Uranus or Neptune. It was at this point in simulations, Jupiter often throws the frost giant in the galaxy.
This is a dilemma trying to decide Nesvorny without breaking everything else in the simulations that really worked. Additional ice giant would take over the main part of the head of Jupiter, allowing other events of the narrative unfold gradually and seamlessly.
“It’s absolutely plausible,” says Batygin. “If you ask, is there any reason why we should be two, not three ice giant, the answer is: of course not.” In fact, according to him, some calculations show that was originally created not more than five naturopathic worlds.
Batygin and his colleagues studied this question simultaneously with Nesvorny, although their motives were different. “I wanted to demonstrate that no additional giant planets can not be,” he says.
He reasoned that this alleged planet, moving from the Solar system, would break that part of the Kuiper belt known as the cold classical belt. If the Kuiper belt was a doughnut, says Batygin, cold classical belt would be his chocolate filling is a family of objects whose orbits lie almost in one plane in the Kuiper belt. Passing planet would be outraged these orbits, consider Batygin and his colleagues.
Their computer simulations showed that this did not happen. Moreover, to their surprise, the ejected planet would have destroyed the cold classical belt. It doesn’t prove the existence of the planet — only says that Solar planet works, how it works, regardless of whether she was there or not. Can this planet to leave a greater signature? Or, returning to the analogy of a crime scene, any tire tracks? Nesvorny believes that could.
Track taken
There is another part of the Kuiper belt, called the kernel, a narrow stream of ice fragments, the orbits of which are currently not synchronized with Neptune. The origin of the nucleus is in some sense a mystery. In 2015 Nesvorny said that this could be a jump in the external migration of Neptune caused by emission of the planet.
When Neptune went into its final orbit and wiped away the debris with orbits that are synchronized with his own, “blow” at the right time could run part of the wreckage like an independent thread, the “core”. Simulations show that gravitational push which forced Jupiter to jump and push out the extra planet, could happen just at the right time to shift the Neptune.
The truth is, we may never know for sure what happened in the formative years of the Solar system. “We can not write the Bible of the Solar system,” says Batygin. “Only vaguely sketch of its history”.
If the Solar system really threw one of his, he is in good company. In recent years astronomers have found a few wandering planets, which were also thrown out of their homes. Moreover, calculations show that in the galaxy floating planets more like Jupiter than the stars.
Billions of refugees. Our fugitive was probably about the size of Neptune and we do not know how many others like him wandering the galaxy. But we know that the universe is full of small things than large.
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Ilya Hel