Radio Observations as an Extrasolar Planet Discovery and Characterization: Interior Structure and Habitability

TL;DR

Radio emissions from planets, caused by magnetic fields and electron cyclotron maser instability, can potentially be used to discover and characterize extrasolar planets and assess their habitability.

Contribution

This paper reviews the potential of radio observations to detect extrasolar planets and infer their interior properties and habitability, highlighting recent advances and future prospects.

Findings

No unambiguous detection of extrasolar planet radio emission yet.

Radio emissions can indicate planetary magnetic fields and interior properties.

Future telescopes may enable detection and characterization of extrasolar planets.

Abstract

Detection of radio emission from Jupiter was identified quickly as being due to its planetary-scale magnetic field. Subsequent spacecraft investigations have revealed that many of the planets, and even some moons, either have or have had large-scale magnetic fields. In the case of the Earth, Jupiter, Saturn, Uranus, and Neptune, the their magnetic fields are generated by dynamo processes within these planets, and an interaction between the solar wind and their magnetic fields generates intense radio emission via the electron cyclotron maser instability. In the case of Jupiter, its magnetic field interacts with the moon Io to result in radio emission as well. Extrasolar planets reasonably may be expected to generate large-scale magnetic fields and to sustain an electron cyclotron maser instability. Not only may these radio emissions be a means for discovering extrasolar planets, because magnetic fields are tied to the properties of planetary interiors, radio emissions may be a remote sensing means of constraining extrasolar planetary properties that will be otherwise difficult to access. In the case of terrestrial planets, the presence or absence of a magnetic field may be an indicator for habitability. Since the first edition of the Handbook, there have been a number of advances, albeit there remain no unambigous detection of radio emission from extrasolar planets. New ground-based telescopes and new possibilities for space-based telescopes provide promise for the future.