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Kuiper Belt

Evidence for a Ninth Planet

The six most distant objects in the solar system (magenta) all mysteriously align. Planet Nine, if it had 10 times Earth’s gravity and an anti-aligned orbit to these distant objects (orange), would explain these paths almost perfectly. (Image: Caltech)

By Dr. Lisa Will, Resident Astronomer at the Reuben H. Fleet Science Center

You may have heard that there is evidence of a possible new ninth planet in our solar system, but what exactly does that mean? What evidence was found?