The Brute-Force Search for Planet Nine

TL;DR

This paper explores a method to detect Planet 9 by measuring gravitational perturbations with spacecraft and telescopes, reducing technological constraints and enabling additional solar system mapping.

Contribution

It proposes a less technologically demanding detection approach for Planet 9 using existing telescopic and spacecraft data, enhancing sensitivity and utility.

Findings

High-precision clocks can be replaced with telescopic measurements.

Spacecraft can map gravitational perturbations even without Planet 9.

The method improves detection sensitivity while relaxing technological constraints.

Abstract

A recent proposal for the detection of a hypothetical gravitating body 500 AU from the Sun (termed Planet 9) calls for a fleet of near-relativistic spacecraft, equipped with high-precision clocks, to be sent to a region where the object is suspected to be. We show that the technological constraints of such a mission can be relaxed somewhat, while improving the sensitivity: high-precision clocks can be avoided when the transverse displacement induced by Planet 9 is measurable with Earth-based, or near-Earth, telescopes. Furthermore, we note that in the absence of Planet 9, these spacecraft still yield useful data by mapping gravitational perturbations in the outer parts of the solar system.