Astronomers spot evidence of volcanically active exomoon

By Brooks Hays
Astronomers spot evidence of volcanically active exomoon
The tidal forces exerted on the theoretical moon by the exoplanet and its sun would stabilize the moon's orbit, researchers found, as well as heat up its insides and trigger volcanic activity. Photo by Thibaut Roger/University of Bern

Aug. 29 (UPI) -- Scientists may have found a volcanically active moon outside our solar system.

Hints of the moon's presence were discovered hiding in the WASP-49 solar system. Astronomers likened the moon to Io, the most volcanically active body in our solar system.


They also likened the moon to a satellite from Star Wars, the planet Mustafar, where Darth Vader's castle is located.

"It would be a dangerous volcanic world with a molten surface of lava, a lunar version of close-in Super Earths like 55 Cancri-e, a place where Jedis go to die, perilously familiar to Anakin Skywalker," Apurva Oza, postdoctoral fellow at the Physics Insitute of the University of Bern in Switzerland, said in a news release.

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Though researchers aren't conjuring the so-called exo-Io from thin air, it's possible the moon, like Mustafar, is science fiction. Or, it could be real, like 55 Cancri-e, also known as Planet Janssen, which orbits the star Copernicus about 41 light years from Earth.

Astronomers haven't directly observed it, only detected a spike in sodium gas surrounding the exoplanet WASP 49-b at an unusually high elevation.

"The neutral sodium gas is so far away from the planet that it is unlikely to be emitted solely by a planetary wind," Oza said.

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Scientists analyzed Jupiter and Io and conducted a series of mass loss calculations to predict where a sodium-emitting moon would be positioned around a faraway planet such as WASP 49-b. The research will soon be published in The Astrophysical Journal.

"The sodium is right where it should be," said Oza.

Researchers at the University of Virginia previously determined that a trio of a star, close-in giant planet and moon could remain stable for billions of years. Oza participated in the early research while a doctoral student at Virginia.

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In such a system, strong tidal forces -- the back-and-forth gravitational tug-of-war -- would help stabilize the moon's orbit, as well as heat its inside, triggering volcanic activity. A rocky, volcanic moon, scientists determined, would be more likely to produce sodium and potassium than a giant gas planet.

"Sodium and potassium lines are quantum treasures to us astronomers because they are extremely bright," said Oza. "The vintage street lamps that light up our streets with yellow haze, is akin to the gas we are now detecting in the spectra of a dozen exoplanets."

Though an exomoon similar to Io offers the best explanation for the spectral observations, there are other possibilities. The sodium could represent a ring of ionized gas surrounding the planet.

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Scientists hope additional observations using both ground-based observatories and space telescopes will yield additional clues.

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