The "Drake equation" of exomoons -- a cascade of formation, stability and detection

TL;DR

This paper explores the complex, interdisciplinary process of detecting exomoons by analyzing formation, stability, and observability, emphasizing the challenges and structure of the problem rather than providing quantitative solutions.

Contribution

It applies a cascade framework inspired by the Drake equation to outline the key steps and challenges in exomoon detection, highlighting the interdisciplinary nature of the problem.

Findings

Identification of three critical steps: formation, stability, and observability.

Emphasis on the complexity and interdisciplinary challenges of exomoon detection.

Highlighting the importance of data analysis considering noise and sampling effects.

Abstract

After 25 years of the prediction of the possibility of observations, and despite the many hundreds of well studied transiting exoplanet systems, we are still waiting for the announcement of the first confirmed exomoon. We follow the ``cascade'' structure of the Drake equation, but apply it to the chain of events leading to a successful detection of an exomoon. The scope of this paper is to reveal the structure of the problem, rather than to give a quantitative solution. We identify three important steps that can lead us to discovery. The steps are the formation, the orbital dynamics and long-term stability, and the observability of a given exomoon in a given system. This way, the question will be closely related to questions of star formation, planet formation, 5 possible pathways of moon formation; long-term dynamics of evolved planet systems involving stellar and planetary rotation and internal structure; and the proper evaluation of the observed data, taking the correlated noise of stellar and instrumental origin and the sampling function also into account. We highlight how a successful exomoon observation and the interpretations of the expected further measurements prove to be among the most complex and most interdisciplinary questions in astrophysics.