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In 2006, Pluto was expelled from the ranks of the "Nine Planets" after being recognized as the ninth planet in the solar system.
However, the expulsion of Pluto, which is almost a matter of course, has drawn the attention of scientists to the region at the edge of the solar system, and even proposed new theories that there may be a planet hidden behind its light at the edge of the solar system.
Because the planet has not yet been discovered by humans, and not all scientists believe it exists, it was thought to be the ninth planet, and it was later thought that it could be a black hole among many speculations and hypotheses.
However, there is a planet that is inextricably linked to Planet Nine, which scientists have observed on an exoplanet, and the orbit of this exoplanet is like telling people that Planet Nine really exists.
However, the exoplanet has revealed to scientists another identity of Planet Nine – a black hole.
1. Identification of the ninth planet.
In 2006, after years of debate by the International Astronomical Union, Pluto was finally "demoted" to a "dwarf planet", and humanity has since reduced the number of large planets in the solar system from nine to eight.
However, since then, with the continuous development of science and technology, a number of new asteroids, dwarf planets and other strange small celestial bodies have been discovered, is there really only these planets and dwarf planets in the solar system, and speculation about whether there is a planet hidden outside Pluto in the solar system has also arisen.
In 2014, American astronomer Brown, with funding from the American Scientific Russia Alliance Research Foundation, made more detailed observations of small objects at the edge of the solar system, and over several years, discovered a number of small objects outside Neptune's orbit.
However, scientists were surprised that they found that the orbits of these small celestial bodies are very special, normally speaking, the orbits of various celestial bodies in the solar system are almost coplanar, orbiting in the same plane, but the orbits of these small celestial bodies are not in the same plane, and there is obvious overlap between orbits.
Brown and his research team then conducted further analysis of the orbits of these small objects, and speculated on the characteristics of the orbits of these small objects, but the orbits of these small objects did not match any other known objects, so Brown suggested that it may be because of the mass of a planet in the solar system, its gravity splits the orbits of these small objects, which makes the orbits of these small objects so special.
Brown also pointed out in the paper that this planet is very likely to be a hidden planet in the solar system, about 5-10 times the mass of the Earth, and because it has not yet been discovered, it is called Planet Nine.
However, as soon as this news came out, it immediately caused a heated discussion among scientists, and some scientists agreed with Brown's view that it is indeed possible that there is indeed a ninth planet in the solar system.
Other scientists are skeptical, believing that Brown's view is not valid, because the planets in the solar system were formed at the beginning of the formation of the primitive solar system, just like the nine planets, they were formed with the sun billions of years ago, and their orbits have been stable for billions of years, so Brown believes that there are other planets in the solar system that have no scientific basis at all, and it is also contrary to the formation and evolution process of the solar system.
Therefore, they believe that Brown is only dissatisfied with being "fired" by scientists because of the expulsion of Pluto, so he makes an unreliable hypothesis.
After Brown, some scientists have further discussed and evaluated Brown's views, such as the American astronomer Mark Hunt, who believes that Brown's views are not unfounded.
Because, as Brown said, a more massive star in the solar system could indeed exist, which can be seen from the orbital characteristics of the group of small objects outside Neptune's orbit, because the reason why the orbits of these small bodies are so tilted is probably due to the presence of this planet.
And Brown thinks that this planet existed at the beginning of the formation of the solar system, has existed for billions of years, and was not finally waited out by the solar system, which is also very possible, because in the process of waiting for the solar system, the sun will often pass by exostars, which will bind some wandering planets to the interior of the solar system to form satellites, so it is entirely possible that there is a planet with a mass greater than the earth.
However, based on the opinions of Brown and other scientists, scientists still have no conclusive evidence for the existence of Planet Nine, because the orbits of the group of small objects discovered by Brown do not clearly indicate the existence of Planet Nine in the solar system, nor can they determine the location and orbit of Planet Nine.
二、HD106906b。
However, the mystery of Planet 9 does not seem to be over, and in 2013, another small object was discovered outside the orbit of Neptune.
However, this small group of objects is different from the group of small objects discovered by Brown because their orbits are all inclined, and the positions and angles of their orbits are also different, which makes the orbits of these small objects even more bizarre.
However, when American astronomers Hugh Rosenweig and Alina Fischer observed the orbits of this group of small objects, they found that the orbits of these small bodies seemed to resonate at one point, which also means that the orbits of these small bodies were affected by a single planet.
However, the position and orbit of this point are very different from Brown's speculation on Planet Nine, so Rosenwig and Fischer believe that this point exists for another reason.
In addition to this point, they also found that several of the small objects in this group of small objects also had similar resonance, which further confirmed that the orbit of this group of small objects was affected by a strong gravitational pull, and also suggested that this gravitational force was caused by an asteroid.
However, scientists have struggled to study the location and orbit of this point, because it is impossible to deduce the asteroid's actual orbit from the orbit of this group of small objects, nor can it be linked to Planet Nine, which Brown suspects.
However, at this time, scientists found an asteroid named HD106906b outside the system, the asteroid's orbit is also very bumpy, it is less than 2 billion kilometers away from its parent star HD106906, and its orbital period has reached 15,000 years, which is almost longer than the orbital period of all planets in the solar system.
This orbital period is also very interesting because, as scientists know, the orbital period of a planet is inversely proportional to its distance from its parent star.
However, HD106906b is very small at a distance of only 7 AU from the Earth to the Sun, while its orbital period is very long, suggesting that the parent star of this system is very massive and too large for scientists to believe.
In order to verify the possibility of the existence of HD106906b, scientists conducted a series of observations and finally confirmed that HD106906b is indeed an exoplanet, but not the kind of exoplanet that humans imagined.
The exoplanet has a very large mass, reaching 10 Jupiter masses, and it is also very close to its parent star, in addition to that, it is a very young system, which leaves scientists with a big mystery.
However, as scientists explore the mystery, it suddenly dawns on someone that HD106906b's orbital period and its distance from its parent star are very similar to the Planet Nine that Brown is talking about.
So scientists have come to a new conclusion, arguing that Planet Nine is likely to have formed at the beginning of the formation of the solar system, but at the same time as the formation of the solar system, the outer solar planets were also formed outside the solar system, and these extrasolar planets, like the sun, were also formed through clouds of gas.
However, because the mass of these extrasolar planets is too large to form in the thin gas clouds within the solar system, these planets wander until they are bound by the sun's gravity and form extrasolar planets.
The ninth planet that Brown suspects is one of them, and HD106906b is also the same as Brown's suspected ninth planet, both of which are extrasolar planets.
Other scientists, however, have a different view, arguing that if Planet Nine is indeed an extrasolar planet, then even if there are many extrasolar planets, there cannot be an extrasolar planet that formed before the formation of the solar system, and there can be no extrasolar planet that formed after the formation of the original solar system.
Because after the formation of the primitive solar system, the sun and extrasolar planets will often "pass by" with extrasolar stars and other planets, so that the extrasolar planets will be brought to the interior of the solar system to form planets, and it is impossible for extrasolar planets to exist after the formation of the solar system.
Therefore, the existence of Planet Nine seems a bit far-fetched, and as Brown said, this Planet Nine is not equal to the solar system, which is even more unrelated than the fact that it is an extrasolar planet.
3. Planets or black holes.
Other scientists have a more different idea, arguing that even if Planet Nine exists, it is entirely possible that it would be a primordial black hole rather than a planet because of its massive mass.
Because stars with masses several orders of magnitude greater than the mass of the Sun often form a black hole after the explosion, because the explosion will reduce their mass, but because the mass is too large, they still cannot resist their own gravity and will eventually collapse into a black hole.
But planets with masses only 5-10 times the size of Earth cannot form a black hole at all, so it is entirely possible that Planet 9 is a primordial black hole and not the planet that Brown suspects.
However, it has also been pointed out that whatever Planet 9 is, whether it exists or not, and what its orbit and nature are, will have to wait for more empirical data to become available, as well as technological breakthroughs, to be confirmed.
So at the moment scientists can only wait, there is no more way.
epilogue
Although scientists have conducted a lot of research on the orbits and properties of the large planets in the solar system from the formation and evolution of the solar system and the evolution of the entire universe, and put forward a series of hypotheses and theories, these are not enough to show that human beings can detect and confirm the existence of a ninth planet in the solar system.
At present, scientists' cognition of whether there is a ninth planet in the solar system is still on assumptions, and they hope to find traces of the ninth planet by observing small celestial bodies at the edge of the solar system as soon as possible, and also hope that human science and technology can break through the bottleneck, provide better conditions and equipment, and help human beings explore more mysteries in the solar system.