Studying Exoplanets in the Radio from the Moon

TL;DR

This paper proposes using lunar-based radio telescopes to detect low-frequency auroral emissions from exoplanets, overcoming Earth's ionospheric limitations and enabling new insights into exoplanet magnetic fields and habitability.

Contribution

It outlines a strategic plan for lunar radio arrays to study exoplanet magnetospheres, including upcoming missions and future large-scale arrays like FarView and FARSIDE.

Findings

Upcoming lunar missions will set upper limits on exoplanet radio flux below 10 MHz.

Lunar arrays can detect magnetic fields of diverse exoplanets, including terrestrial ones.

Potential to significantly advance understanding of exoplanet habitability and magnetic properties.

Abstract

Exoplanets with and without a magnetic field are predicted to form, behave, and evolve very differently. Therefore, there is great need to directly constrain these fields to holistically understand the properties of exoplanets including their potential habitability. This goal aligns with the Astro2020 Decadal Survey recommendations. Observing planetary auroral radio emissions is among the most promising detection methods, but decades of searching have yet to yield a conclusive detection, though promising hints are now emerging from ground-based radio telescopes. However, these ground-based efforts are fundamentally limited by Earth's ionosphere, which blocks the low-frequency signals (<10 MHz) expected from terrestrial and Neptune-like exoplanets. In this white paper, we outline a strategy to overcome this barrier by utilizing the unique environment of the Moon. We discuss how the upcoming LuSEE-Night and ROLSES pathfinder missions will study our Solar System's planets as exoplanet analogs and place the first meaningful upper limits on exoplanetary radio flux below 10 MHz. Furthermore, we explore the revolutionary potential of the proposed future lunar arrays FarView and FARSIDE. For example, FarView will be sensitive enough to study the magnetic fields of a diverse set of exoplanets (super-Earths to gas giants) and an order of magnitude more Jupiter-like planets than ground-based telescopes, providing crucial tests for dynamo theory. Most significantly, FARSIDE will be able to detect the magnetospheres of nearby terrestrial exoplanets, offering a powerful synergy with atmospheric characterization efforts by JWST and HWO to fully assess their potential habitability. By opening this unexplored low-frequency window, radio astronomy from the Moon is poised to transform the field of exoplanet magnetospheric science. [Abridged]