Planet Nine (IMAGE) California Institute of Technology Caption This illustration depicts orbits of distant Kuiper Belt objects and Planet Nine. Orbits rendered in purple are primarily controlled by Planet Nine's gravity and exhibit tight orbital clustering. Green orbits, on the other hand, are strongly coupled to Neptune, and exhibit a broader orbital dispersion. Updated orbital calculations suggest that Planet Nine is an approximately 5 Earth mass planet that resides on a mildly eccentric orbit with a period of about ten thousand years. Credit James Tuttle Keane/Caltech Usage Restrictions For use in news stories only License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.