A Far-Infrared Search for Planet Nine Using AKARI All-Sky Survey

Abstract

An unusual orbital element clustering of Kuiper belt objects (KBOs) has been observed. The most promising dynamic solution is the presence of a giant planet in the outer Solar system, Planet Nine. However, due to its extreme distance, intensive searches in optical have not been successful. We aim to find Planet Nine in the far-infrared, where it has the peak of the black body radiation, using the most sensitive all-sky far-infrared survey to date, AKARI. In contrast to optical searches, where the energy of reflected sunlight decreases by $d^4$, thermal radiation in the infrared decreases with the square of the heliocentric distance $d^2$. We search for moving objects in the AKARI Single Scan Detection List. We select sources from a promising region suggested by an N-body simulation from Millholland and Laughlin 2017: $30^{\circ }<$ R.A. $<50^{\circ }$ and $-20^{\circ }<$ Dec. $<20^{\circ }$. Known sources are excluded by cross-matching AKARI sources with 9 optical and infrared catalogues. Furthermore, we select sources with small background strength to avoid sources in the cirrus. Since Planet Nine is stationary in a timescale of hours but moves on a monthly scale, our primary strategy is to select slowly moving objects that are stationary in 24 hours but not in six months, using multiple single scans by AKARI. The selected slowly moving AKARI sources are scrutinised for potential contamination from cosmic rays. Our analysis reveals two possible Planet Nine candidates whose positions and flux are within the theoretical prediction ranges. These candidates warrant further investigation through follow-up observations to confirm the existence and properties of Planet Nine.

12 pages, 8 figures, 2 tables. Accepted for publication in Publications of the Astronomical Society of Australia. For more information, see https://docs.google.com/document/d/1WUfVFAe-cWPEq4YJVCMagR3PaN_dudgWsGs9oZnVvQc/edit?usp=sharing

References in corpus (15)

• The unWISE Catalog: Two Billion Infrared Sources from Five Years of WISE Imaging
• The CatWISE2020 Catalog
• The Type Icn SN 2021csp: Implications for the Origins of the Fastest Supernovae and the Fates of Wolf-Rayet Stars
• The Core Collapse Supernova Rate from the SDSS-II Supernova Survey
• OSSOS VI. Striking Biases in the detection of large semimajor axis Trans-Neptunian Objects
• New Extreme Trans-Neptunian Objects: Towards a Super-Earth in the Outer Solar System
• A parametric description of the 3D structure of the Galactic Bar/Bulge using the VVV survey
• The volumetric rate of normal type Ia supernovae in the local universe discovered by the Palomar Transient Factory
• Constraints on Planet Nine's Orbit and Sky Position within a Framework of Mean Motion Resonances
• Orbital clustering in the distant solar system
• Herschel limits on far-infrared emission from circumstellar dust around nearby Type Ia supernovae
• Searching for Planet Nine with Coadded WISE and NEOWISE-Reactivation Images
• A search for Planet Nine using the Zwicky Transient Facility public archive
• A search for Planet 9 in the IRAS data
• Searching for giant planets in the outer Solar System with far-infrared all-sky surveys

Cited by in corpus (1)

• Dark matter heating of Planet 9, and its observational implications