Constraints on the location of a possible 9th planet derived from the Cassini data

TL;DR

This study uses planetary ephemerides and Cassini data to constrain the possible location of a hypothesized 9th planet in the outer solar system, ruling out certain positions and suggesting a most probable true anomaly.

Contribution

It provides the first constraints on the location of a potential 9th planet based on Cassini data, refining previous hypotheses about its orbit.

Findings

Certain true anomaly intervals are incompatible with Cassini data.

The addition of the proposed planet can improve residuals at a specific true anomaly.

Constraints narrow down the possible position of the hypothesized planet.

Abstract

To explain the unusual distribution of Kuiper Belt objects, several authors have advocated the existence of a super-Earth planet in the outer solar system. It has recently been proposed that a 10 M$_{\oplus}$ object with an orbit of 700 AU semi major axis and 0.6 eccentricity can explain the observed distribution of Kuiper Belt objects around Sedna. Here we use the INPOP planetary ephemerides model as a sensor for testing for an additional body in the solar system. We test the possibility of adding the proposed planet without increasing the residuals of the planetary ephemerides, fitted over the whole INPOP planetary data sample. We demonstrate that the presence of such an object is not compatible with the most sensitive data set, the Cassini radio ranging data, if its true anomaly is in the intervals $[-130^\circ:-100^\circ]$ or $[-65^\circ : 85^\circ]$. Moreover, we find that the addition of this object can reduce the Cassini residuals, with a most probable position given by a true anomaly $v = {117.8^\circ}^{ + 11^\circ}_{ - 10^\circ} $.