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WISE’s survey of the sky in infrared has now shown that there is no large planet X orbiting beyond Pluto.
This recent study, which involved an examination of WISE data covering the entire sky in infrared light, found no object the size of Saturn or larger exists out to a distance of 10,000 astronomical units (au), and no object larger than Jupiter exists out to 26,000 au. One astronomical unit equals 93 million miles. Earth is 1 au, and Pluto about 40 au, from the sun. “The outer solar system probably does not contain a large gas giant planet, or a small, companion star,” said Kevin Luhman of the Center for Exoplanets and Habitable Worlds at Penn State University, University Park, Pa., author of a paper in the Astrophysical Journal describing the results.
The theory, popular among planetary scientists and journalists, is that this theorized distant planet would periodically disturb the orbits of comets in the Oort Cloud, sending them raining down on Earth and thus cause the periodic extinction events found in the paleontological record. It was a cute theory, but based on little data. Now we have the data, and no such planet exists.
The data has found a lot of previously unknown nearby stars and brown dwarfs, which is significant in that they are close and can be studied more easily.