A Quantitative Criterion for Defining Planets

TL;DR

This paper introduces a straightforward quantitative metric based on star and planet properties to classify planets and exoplanets, simplifying the planetary definition process.

Contribution

It proposes a new, easy-to-apply criterion for defining planets using minimal data, applicable to most known exoplanets.

Findings

All 8 planets satisfy the criterion.

99% of known exoplanets can be classified using this metric.

The criterion effectively distinguishes planets from other celestial objects.

Abstract

A simple metric can be used to determine whether a planet or exoplanet can clear its orbital zone during a characteristic time scale, such as the lifetime of the host star on the main sequence. This criterion requires only estimates of star mass, planet mass, and orbital period, making it possible to immediately classify 99% of all known exoplanets. All 8 planets and all classifiable exoplanets satisfy the criterion. This metric may be useful in generalizing and simplifying the definition of a planet.