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Given the extravagant profusion of moons in our own solar system, it seems likely that there are many more exomoons in the universe than exoplanets. We have not found one conclusively yet – but astronomers have just found a signal that could indicate the presence of an exoon.
Not any exomoon either, but something that looks like a lifting version of the jovian moon Io, the most volcanoically active object of the solar system.
And we really want to say fucking. Not only would the exomoon be covered with volcanoes spewing lava, it would gravitate around a burning planet – WASP-49b, a gigantic gas giant planet known as the hot Jupiter, moving around. the yellow dwarf star WASP-49 every 2.8 days.
"It would be a dangerous volcanic world with a molten lava surface, a lunar version of near-super-lands like the 55 Cancri-e," said astrophysicist Apurva Oza of the Institute of Physics & Disease. University of Bern.
But do not pack your lava suits for now. The team did not detect the exomo directly. They deduced that it existed from data from the planet itself, from elements detected in the upper atmosphere.
When publishing an article describing the atmosphere of WASP-49b in 2017, researchers found the presence of a thick layer of sodium at an unusually high altitude, without clouds. This layer of sodium has prompted the international team of Oza to take a closer look.
"The sodium-free gas is so far away from the planet that it is unlikely that it will be emitted solely by a global wind," he said.
We know, based on observations closer to home, that volcanic activity on Io produces quite heavy amounts of potassium and sodium (among others). These do not cling in significant amounts to the moon, but are drawn into the complex magnetosphere of Jupiter, creating a torus of matter that rings on the planet.
We also know that without the intense gravitational interaction between Io and Jupiter generated by the moon's elliptical orbit – the variable tidal forces that create friction and therefore heat in the moon – it would not be volcanically active.
In 2006, another team of researchers extrapolated that the presence of a torus of materials around a planet could imply the presence of a moon or other body in orbit.
The team has therefore encrypted some figures. And they discovered that a volcanically active exomoon could release more potassium and sodium than the planet on which it runs.
The Oza team concluded that the sodium and potassium around WASP-49b, in quantity and at the odd altitude detected, would likely have been vomited by a volcanic lunar moon. But it is also plausible that other processes or phenomena are responsible for it – an ionized gas ring, for example.
Again, further observation would help to find answers – a more detailed analysis of the spectrum of the planet. The sodium and potassium lines on the spectrum are very strong; by looking more closely, researchers hope to find weaker signals from other volcanic volatiles in the planet 's atmosphere, such as sulfur and oxygen.
In addition, this provides another excellent reason to probe the atmosphere of exoplanets – a task to which we hope the next generation of telescopes will excel.
"While the current wave of research is focusing on habitability and biosignatures, our signature is a signature of destruction," Oza said. "The interesting part is that we can monitor these destructive processes in real time, like fireworks."
The search was accepted in The astrophysical journal, and is available on arXiv.
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