## Planet Definition Proposal

As published in the Astronomical Journal (2015)
Poster describing the proposal.
Peer-reviewed paper describing the proposal: J. L. Margot.
A Quantitative Criterion for Defining Planets.

### Introduction

The IAU definition of 'planet' needs improvement because it is neither quantitative nor general. I proposed a simple criterion that can be used to quantify, generalize, and simplify the definition. This criterion makes it possible to immediately classify 99% of all known exoplanets. All 8 planets and all classifiable exoplanets satisfy the criterion.

### Planet test applied to solar system bodies

The figure below shows the criterion applied to the solar system (objects above the bold line are planets according to this criterion):

### Planet test applied to the putative Planet Nine

Would Planet Nine pass the planet test? The answer is yes.

### References

*Astronomical Journal*

**150**, 185, 2015.