Testing quasilinear modified Newtonian dynamics in the Solar System

TL;DR

This paper models the Solar System's gravitational potential to test quasi-linear MOND predictions near saddle points, especially in the Earth-Sun system, using high-precision data and considering spacecraft sensitivity.

Contribution

It provides a detailed model of saddle points in the Solar System and assesses the detectability of MOND effects with upcoming spacecraft missions.

Findings

Earth-Sun saddle point may be visited by LISA Pathfinder

Certain interpolating functions can evade detection in null results

Saturn's outer satellites periodically enter the MOND regime

Abstract

A unique signature of the modified Newtonian dynamics (MOND) paradigm is its peculiar behavior in the vicinity of the points where the total Newtonian acceleration exactly cancels. In the Solar System, these are the saddle points of the gravitational potential near the planets. Typically, such points are embedded into low-acceleration bubbles where modified gravity theories a` la MOND predict significant deviations from Newton's laws. As has been pointed out recently, the Earth-Sun bubble may be visited by the LISA Pathfinder spacecraft in the near future, providing a unique occasion to put these theories to a direct test. In this work, we present a high-precision model of the Solar System's gravitational potential to determine accurate positions and motions of these saddle points and study the predicted dynamical anomalies within the framework of quasi-linear MOND. Considering the expected sensitivity of the LISA Pathfinder probe, we argue that interpolation functions which exhibit a "faster" transition between the two dynamical regimes have a good chance of surviving a null result. An example of such a function is the QMOND analog of the so-called simple interpolating function which agrees well with much of the extragalactic phenomenology. We have also discovered that several of Saturn's outermost satellites periodically intersect the Saturn-Sun bubble, providing the first example of Solar System objects that regularly undergo the MOND regime.