Debate: Is it likely that another planet exists?

Scientists are conflicted about the existence of a ninth Solar System member

Yes

If another world is not there you need other theories to explain each of the anomalous patterns we see. You need a theory to explain why the orbits are aligned together, a theory to explain why objects are out of the reach of Neptune and another to explain why some orbits get flipped upside down. Another planet explains all of these anomalies consistently.

Konstantin Batygin, California Institute of Technology

No

A small group of us are working on an alternative hypothesis which involves the collective gravity of minor planets. These minor planets orbit so far away from the Sun and the major planets that the weak gravity acting between them can build up slowly over time and come to dominate their dynamical evolution. They can rearrange their own orbits into a distribution similar to what we observe in the outer

Solar System without the need for another planet. This explanation predicts that there is a disc of minor planets more massive than the Kuiper Belt awaiting discovery at hundreds of AU.

Ann-Marie Madigan, University of Colorado, Boulder