Sun flux variation due to the effects of orbiting planets. Case of study of a non-compact planetary system

TL;DR

This study models the phase curves of Solar System planets considering reflection, ellipsoidal, and Doppler effects, revealing Doppler beaming as the dominant factor influencing light curve variations for an external observer.

Contribution

It provides the first detailed theoretical predictions of planetary light curves in a non-compact system like the Solar System, with well-known parameters for accurate modeling.

Findings

Doppler beaming is generally the dominant effect in planetary light curve variations.

Ellipsoidal effects are very weak across the studied planets.

Mercury and Venus show comparable amplitudes for Doppler and reflection effects.

Abstract

We study the phase curves for the planets of our Solar System; which, is considered as a non-compact planetary system. We focus on modeling the small variations of the light curve, based on the three photometric effects: reflection, ellipsoidal, and Doppler beaming. Theoretical predictions for these photometric variations are proposed, as if a hypothetical external observer would measure them. In contrast to similar studies of multi-planetary systems, the physical and geometrical parameters for each planet of the Solar System are well-known. Therefore, we can evaluate with accuracy the mathematical relations that shape the planetary light curves for an external fictitious observer. Our results suggest that in all the planets of study the ellipsoidal effect is very weak, while the Doppler beaming effect is in general dominant. In fact, the latter effect seems to be confirmed as the principal cause of variations of the light curves for the planets. This affirmation could not be definitive in Mercury or Venus where the Doppler beaming and the reflection effects have similar amplitudes. The obtained phase curves for the Solar System planets show interesting new features that have not been presented before, so the results presented here are relevant in their application to other non-compact systems, since they allow us to have an idea of what it is expected to find in their light curves.