Or how about 10 times the size of Earth?
Researchers at Caltech have finally found substantial evidence that a planet exists within a unique orbit in the outer solar system. Granted, this planet has not been observed directly yet (the picture above is an artist's rendering, R. Hurt at Caltech). However, researchers Konstantin Batygin and Mike Brown used mathematical modeling and complex computer models and simulations to determine the identity of the ninth planet. "Although we were initially quite skeptical that this planet could exist, as we continued to investigate its orbit and what it would mean for the outer solar system, we became increasingly convinced that it is out there," says Batygin. "For the first time in over 150 years, there is solid evidence that the solar system's planetary census is incomplete."
Since the beginning of the debate on whether extreme Kuiper Belt objects existed, the idea of a planet far out in the Kuiper Belt was tossed around. However, the idea never really took root, for the observation of such a planet was never seen, and data was inconclusive. Beginning in 2014, the idea based on a paper published by Chad Trujillo and Scott Sheppard arose from the observation on distant objects in the Kuiper Belt and their obscure orbital feature. Brown brought is thoughts to Batygin, and the two worked for a year and a half on this problem.
Their efforts on observing the Kuiper belt and the many objects within slowly brought forth fruit. They initially saw that 6 objects had elliptical orbits that fell within the same direction in physical space, indicating that something was affecting the orbits. Secondly, they disproved that the simple amount of objects would affect the orbits of the 6 objects, calculating that the Kuiper Belt would require over 100 times the amount of mass it has today. Finally, after numerous computer simulations, they discovered that a massive planet in an anti-aligned orbit (180 degrees from all other objects and known planets in the solar system) matched the data that they had received.
"Your natural response is 'This orbital geometry can't be right. This can't be stable over the long term because, after all, this would cause the planet and these objects to meet and eventually collide,'" said Batygin. However, due ti a mechanism known as mean-motion resonance, the massive planet actually propels the objects away from it as the objects in the Kuiper pass by it due to its unique orbit.
So essentially, the evidence for a ninth planet in deep space in our solar system is overwhelming. But it has not been observed just yet. "I would love to find it," says Brown. "But I'd also be perfectly happy if someone else found it. That is why we're publishing this paper. We hope that other people are going to get inspired and start searching [...] All those people who are mad that Pluto is no longer a planet can be thrilled to know that there is a real planet out there still to be found. Now we can go and find this planet and make the solar system have nine planets again."
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