A Search for X-ray emission from Saturn, Uranus and Neptune

TL;DR

This study analyzes X-ray observations of Saturn, Uranus, and Neptune, finding a marginal detection for Saturn and setting upper limits for the others, suggesting similar X-ray production mechanisms across these planets.

Contribution

First-time detection of X-ray emission from Saturn and constraints on Uranus and Neptune's X-ray luminosities, comparing them with Jupiter's emissions.

Findings

Saturn shows a marginal X-ray detection.

Uranus and Neptune's X-ray luminosities are below Jupiter-like levels.

X-ray emissions are consistent with electron precipitation mechanisms.

Abstract

We present an analysis of X-ray observations of the trans-Jovian planets Saturn, Uranus and Neptune with the ROSAT PSPC in comparison with X-ray observations of Jupiter. For the first time a marginal X-ray detection of Saturn was found and 95% confidence upper limits for Uranus and Neptune were obtained. These upper limits show that Jupiter-like X-ray luminosities can be excluded for all three planets, while they are consistent assuming intrinsic Saturn-like X-ray luminosities. Similar X-ray production mechanisms on all trans-Jovian planets can therefore not be ruled out, and spectral shape and total luminosity observed from Saturn are consistent with thick-target bremsstrahlung caused by electron precipitation as occurring in auroral emission from the Earth.