Given the extravagant abundance of the moon in our solar system, it seems that there are many more exons in the universe than there are exoplanets. We are about to finally find one – but astronomers have just found a signal that may indicate the presence of an exomon.
Not just any exomune, but something like a fixed version of the moon Jovian Yo, the most volcanically active object in the solar system.
And we really mean savvy Not only will the exomon be covered with volcanoes radiating lava, it will orbit a hot planet – WASP-49b, a massive gas giant planet known as hot Jupiter, invading around yellow dwarf star WASP-49 once every 2.8 days.  "This would be a dangerous volcanic world with a molten lava surface, a lunar version of a closed Super Earth like 55 Cancri-e," says astrophysicist Apurva Oz, of the University of Bern Institute of Physics.
But don't pack your lavatory suits yet. The team did not directly find the exome. They concluded that it exists based on data from the planet itself ̵
When a book describing the atmosphere of WASP-49b was published in 2017, researchers noted the presence of a thick layer of sodium at an unusually high altitude without clouds. This sodium layer made Oza's international team look closer.
"Neutral sodium gas is so far off the planet that it is unlikely to be emitted by planetary wind alone," he said.
We know from close-to-home observations that volcanic activity on Io produces quite heavy amounts of potassium and sodium (amongst a few other things). They do not cling in significant quantities to the moon, but are absorbed in Jupiter's complex magnetosphere, leading to the fertilizer of material that rings on the planet.
We also know that without the intense gravitational interaction between Io and Jupiter generated by the lunar elliptical orbit – the different tidal forces that create friction and thus heat up in the moon will not be volcanically active.
In 2006, a different team of researchers extrapolated that the presence of a torus of material around the planet could indicate the presence of a moon or other orbital body.
So the team breaks down some numbers. And they found that the volcanically active exomon can actually release more potassium and sodium than the planet it orbits.
Sodium and potassium around WASP-49b, in quantities and at strange altitudes found, concluded by the Oza team, may have been written by a volcanic hellish moon. But it is also plausible that other processes or phenomena – an ionized gas ring – are responsible.
Once again, more observation would help to find the answers – analyzing the spectrum of the planet in more detail. The sodium and potassium lines in the spectrum are very strong; through closer search, researchers hope to find weaker signals of other volcanic volatiles in the planet's atmosphere, such as sulfur and oxygen.
In addition, this provides another excellent reason for exploring extrasolar planets' atmospheres – a task that we hope the next generation of telescopes will differentiate.
"As the current wave of research goes toward habitation and biosignatures, our signature is a signature of destruction," Oz said. "The exciting part is that we can watch these destructive processes in real time, like fireworks."
The studies are accepted in Astrophysical Journal and are available in arXiv.