# A Gap in the Mass Distribution for Warm Neptune and Terrestrial Planets

## TL;DR

This paper identifies a significant new gap in the distribution of warm Neptune and terrestrial planets, revealing insights into planetary formation and evolution processes through statistical analysis of mass and orbital data.

## Contribution

It uncovers a previously unrecognized mass gap in sub-Neptune planets with short orbital periods, supported by statistical modeling and analysis of recent mass measurements.

## Key findings

- Discovery of a mass gap in sub-Neptune planets with periods under 20 days
- The gap has a slope of decreasing mass with increasing period
- Gaussian mixture models favor a bimodal distribution over a unimodal one

## Abstract

Structure in the planet distribution provides an insight into the processes that shape the formation and evolution of planets. The Kepler mission has led to an abundance of statistical discoveries in regards to planetary radius, but the number of observed planets with measured masses is much smaller. By incorporating results from recent mass determination programs, we have discovered a new gap emerging in the planet population for sub-Neptune mass planets with orbital periods less than 20 days. The gap follows a slope of decreasing mass with increasing orbital period, has a width of a few $M_\oplus$, and is potentially completely devoid of planets. Fitting gaussian mixture models to the planet population in this region favours a bimodel distribution over a unimodel one with a reduction in Bayesian Information Criterion (BIC) of 19.9, highlighting the gap significance. We discuss several processes which could generate such a feature in the planet distribution, including a pileup of planets above the gap region, tidal interactions with the host star, dynamical interactions with the disk, with other planets, or with accreting material during the formation process.