A World ‘Where Jedis Go To Die’ Could Be Our First Volcanic ‘Hot Moon’

We know one of the moons of Jupiter has volcanoes and flowing lava. Discovered in 1979 by Voyager 1, there could be 400 active volcanoes on Io, the most volcanically active body in our solar system.

The moons of Enceladus at Saturn and Triton at Neptune are also thought to be volcanic, which begs a question. Are there volcanic “exomoons” in other star systems? Is there an “exo-Io?” If so, what's it like?

Welcome to WASP-49b

Astronomers at the Physics Institute of the University of Bern in Germany think they have found just that, identifying an active moon in a distant exoplanet system called WASP-49. About 550 light years away in the constellation of Lepus (just below Orion’s Belt if you’re stargazing from the northern hemisphere), WASP-49 is a yellow dwarf star with one known planet, WASP-49b, that was discovered in 2011. That exoplanet appears to have a “sodium envelope,” and it’s now thought to be caused by an “exo-Io” moon.

'Where Jedis go to die'

“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,” says Apurva Oza, postdoctoral fellow at the Physics Institute of the University of Bern and associate of the NCCR PlanetS. “It's a place where Jedis go to die, perilously familiar to Anakin Skywalker." This exo-moon, if it does exist, would orbit a hot giant planet–WASP 49-b–which in turn would race once around its host star in less than three days.

What’s the evidence for ‘exo-Io?’

The researchers in Bern conclude that the exo-Io exists from a detection of sodium gas at WASP 49-b at high-altitude. "The neutral sodium gas is so far away from the planet that it is unlikely to be emitted solely by a planetary wind," says Oza. The researchers have compared the observations to what happens with Io in the Jupiter system, and think that an "exo-Io" could be a plausible source of sodium at WASP 49-b. "The sodium is right where it should be" says Oza.

'Quantum treasures'

Building on work from 2006 that suggested that sodium around an exoplanet might indicate an exo-moon or a ring of material, the researchers show that a small rocky moon could eject more sodium and potassium into space if it was extremely volcanically active. "Sodium and potassium lines are quantum treasures to us astronomers because they are extremely bright," says 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."

However, this is just a theory. To date there are no confirmed exo-moon detections, and the anomaly at WASP 49-b could be caused by a ring of ionized gas.

Wishing you clear skies and wide eyes.

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