Radio waves could reveal exomoons

Research on Io could help uncover other moons around distant stars

Credit: University of Texas at Arlington

Interaction between a planet and its satellite can create radio wave emissions.

The hunt for life beyond Earth has gathered pace over the last 20 years, with over 1800 exoplanets already discovered. But, so far no exomoons have been found. Now, new research has shown it might be possible to track these distant moons, hundreds of potential new habitable worlds, using radio telescopes.

No planet hunting method currently in use can detect exomoons, but it might be possible to search for them by looking for signals similar to the ones created by Jupiter’s moon Io. High levels of volcanic activity on the moon have created a highly charged upper atmosphere called an ionosphere. As it orbits Jupiter, the moon’s ionosphere interacts with the planet’s magnetosphere producing radio waves. It’s possible that similar emissions created between an exoplanet and its satellite could be detected from Earth.

“This is a new way of looking at these things,” said Zdzislaw Musielak, professor of physics at the University of Texas. “We said, ‘What if this mechanism happens outside of our Solar System?’ Then, we did the calculations and they show that actually there are some star systems that if they have moons, [they] could be discovered in this way.

Wide reaching

But the technique is not limited to highly volcanic moons such as Io.

“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,” says Joaquin Noyola, a PhD student who took part in the study.

It’s hoped that such discoveries could vastly expand the number of discoverable worlds where life could exist.

“Most of the detected exoplanets are gas giants, many of which are in the habitable zone,” says Suman Satyal, another PhD student working on the project. “These gas giants cannot support life, but it is believed that the exomoons orbiting these planets could still be habitable.”


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