Exoplanets & Exomoons

Radio Observations As An Extrasolar Planet Discovery and Characterization: Interior Structure and Habitability

By Keith Cowing
Status Report
April 19, 2024
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Radio Observations As An Extrasolar Planet Discovery and Characterization: Interior Structure and Habitability
Radio sky in the 30 MHz–43 MHz (left) and 47 MHz–78 MHz bands (right); zenith is at the center of the images. Strong sources are labeled, notably including Jupiter and the Sun. In the lower frequency image, Jupiter is of comparable brightness to the Sun, illustrating that the starplanet intensity ratio can be of order unity at radio wavelengths. In the higher frequency image, the absence of Jupiter is consistent with the exceptionally strong cutoff of cyclotron maser emission where the local plasma frequency exceeds the local cyclotron frequency within the planet’s magnetosphere. (Images courtesy of M. Anderson)

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.

T. Joseph W. Lazio (Jet Propulsion Laboratory, California Institute of Technology)

Comments: To be published in: Handbook of Exoplanets, 2nd Edition, Hans Deeg and Juan Antonio Belmonte (Eds. in Chief), Springer International Publishing AG, part of Springer Nature. Pointers to missed literature welcome
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Geophysics (physics.geo-ph); Space Physics (physics.space-ph)
Cite as: arXiv:2404.12348 [astro-ph.EP] (or arXiv:2404.12348v1 [astro-ph.EP] for this version)
Submission history
From: Joseph Lazio
[v1] Thu, 18 Apr 2024 17:24:56 UTC (2,628 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻