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A new way to search for exomoons

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August 12, 2014

Schematic of a plasma torus around an exoplanet, which is created by the ions injected from an exomoon's ionosphere into the planet's magnetosphere. Image via UT Arlington — Schematic of a plasma torus around an exoplanet, which is created by the ions injected from an exomoon’s ionosphere into the planet’s magnetosphere. Image by Suman Satyal via UT Arlington

In recent years, astronomers have found more than 1,800 exoplanets, worlds located far beyond our local solar system. But, so far, no one has confirmed an exomoon. Physicists from University of Texas at Arlington say it might be possible to follow a trail of radio wave emissions to discover the first exomoons orbiting distant planets. Their work is published in the August 10, 2014 issue of The Astrophysical Journal.

These physicists propose to look for radio wave emissions, like those resulting from the interaction between the magnetic field of Jupiter – our solar system’s largest planet – and its little moon Io. This moon has an ionosphere – a charged upper atmosphere – likely created by Io’s extremely active volcanoes. As Io orbits around Jupiter, its ionosphere interacts with Jupiter’s magnetosphere – a layer of charged plasma that protects the planet from radiation – to create a frictional current that causes radio wave emissions.

The physicists suggest using detailed calculations about the Jupiter/Io dynamic to look for radio emissions that could indicate moons orbiting an exoplanet.

Joaquin Noyola, a Ph.D. graduate student at UT Arlington is lead author on the new paper. He said it’s important to note that – when modeling distant planet/moon pairs – exomoons would not necessarily have to have Io’s volcanic activity to have an ionosphere. He said:

Larger moons – such as Saturn’s largest moon, Titan – can sustain a thick atmosphere, and that could also mean they have an ionosphere. So volcanic activity isn’t a requirement.

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August 12, 2014

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Deborah Byrd

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Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Prior to that, she had worked for the University of Texas McDonald Observatory since 1976, and created and produced their Star Date radio series. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. In 2020, she won the Education Prize from the American Astronomical Society, the largest organization of professional astronomers in North America. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.