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January 25, 2016

Data, Calculations Point to a New Planet

The predicted existence of a new member of our solar system, “Planet Nine,” as astronomers labeled it, is based on theoretical calculations that agree with observational and other data. But the researchers who published the findings predicting the existence of Planet Nine have yet to actually observe the distant body.

Observers note this isn’t the first time astronomers relied heavily on data and theoretical mathematics to discover a planet before it was found by stargazing telescopes. What Caltech astronomers Michael Brown and Konstantin Batygin have actually observed are the movements of six icy bodies well beyond former planet Pluto in a region known as the Kuiper Belt.

In a paper published by The Astronomical Journal on Jan. 20, Brown and Batygin reported that they observed the six objects moving in oblong orbits and were aligned in the same orbital plane. “We demonstrate that the perihelion positions [the point in an orbit closest to the sun] and orbital planes of the objects are tightly confined and that such a clustering has only a probability of 0.007 percent to be due to chance, thus requiring a dynamical origin.”

In other words, something very large but as yet unobserved is causing the icy bodies to lineup like the moons of Jupiter. The Caltech researchers crunched the data gathered by previous researchers and refined their theoretical calculations to postulate a new member of our solar system that could be as much ten times the mass of Earth.

“The agreement between the theoretical calculation and data is more than satisfactory, and is fully consistent with the recent analysis” by other astronomers, Brown and Batygin reported. Previous research focused on other icy bodies at the very edges of our solar system examined the possibility that a massive but unobserved planet had “herded” the objects into alignment.

The Caltech researchers built their research and theoretical calculations on these data, positing an extremely elongated orbit for the possible planet and along with a more detailed mechanism for explaining how the icy bodies are “perturbed.”

Planet Nine could be as large as some of the outer planets, but its projected distance from the sun—perhaps 40 times farther out than Neptune (2.795 billion miles) and an orbit around the sun that might take 10,000 years—means it would reflect very little sunlight. Hence, astronomers have so far been unable to find it. However, the data collected by the Caltech researchers and their calculations that appear to agree with those data have at least given astronomers a better idea of where to point their telescopes in search of Planet Nine.

Other researchers said the Caltech astronomers are on to something. “I’d be willing to bet about 50/50 odds, maybe better, that there’s another planet out there,” Scott Tremaine, an astronomer at the Institute for Advanced Study in Princeton, told the website FiveThirtyEight.

In their paper, Brown and Batygin concluded: “Continued analysis of both distant and highly inclined outer solar system objects provides the opportunity for testing our hypothesis as well as further constraining the orbital elements and mass of the distant planet.”

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