A 3pi Search for Planet Nine at 3.4 microns with WISE and NEOWISE

TL;DR

This study conducts the deepest and widest infrared search for Planet Nine using WISE data, covering over three quarters of the sky and ruling out its presence within specific brightness and location parameters.

Contribution

It extends previous search methods to a broader sky area and longer time span, improving detection sensitivity for Planet Nine at 3.4 microns.

Findings

No Planet Nine detected in the surveyed parameter space.

Established sensitivity limits for Planet Nine detection at W1 < 16.7.

Provided the most comprehensive infrared search for Planet Nine to date.

Abstract

The recent 'Planet Nine' hypothesis has led to many observational and archival searches for this giant planet proposed to orbit the Sun at hundreds of astronomical units. While trans-Neptunian object searches are typically conducted in the optical, models suggest Planet Nine could be self-luminous and potentially bright enough at ~3-5 microns to be detected by the Wide-field Infrared Survey Explorer (WISE). We have previously demonstrated a Planet Nine search methodology based on time-resolved WISE coadds, allowing us to detect moving objects much fainter than would be possible using single-frame extractions. In the present work, we extend our 3.4 micron (W1) search to cover more than three quarters of the sky and incorporate four years of WISE observations spanning a seven year time period. This represents the deepest and widest-area WISE search for Planet Nine to date. We characterize the spatial variation of our survey's sensitivity and rule out the presence of Planet Nine in the parameter space searched at W1 < 16.7 in high Galactic latitude regions (90% completeness).