A search for Planet Nine using the Zwicky Transient Facility public archive

TL;DR

This study searches for Planet Nine in the Zwicky Transient Facility archive, finds no candidates, and constrains the parameter space where Planet Nine could exist based on survey detection limits and synthetic population modeling.

Contribution

It provides the first systematic search for Planet Nine in the Zwicky Transient Facility data and introduces a synthetic population to quantify detection limits.

Findings

No Planet Nine candidates found in the survey.

The survey rules out 56% of the predicted Planet Nine phase space.

Detection efficiency reaches approximately 95% at magnitude V=20.5.

Abstract

Recent estimates of the characteristics of Planet Nine have suggested that it could be closer than originally assumed. Such a Planet Nine would also be brighter than originally assumed, suggesting the possibility that it has already been observed in wide-field moderate-depth surveys. We search for Planet Nine in the Zwicky Transient Facility public archive and find no candidates. Using known asteroids to calculate the magnitude limit of the survey, we find that we should have detected Planet Nine throughout most of the northern portion of its predicted orbit -- including within the galactic plane -- to a 95% detection efficiency of approximately $V=20.5$. To aid in understanding detection limits for this and future analyses, we present a full-sky synthetic Planet Nine population drawn from a statistical sampling of predicted Planet Nine orbits. We use this reference population to estimate that this survey rules out 56% of predicted Planet Nine phase space, and we demonstrate how future analyses can use the same synthetic population to continue to constrain the amount of parameter space effectively searched for Planet Nine.