Jupiter's moon Io is the most volcanically active body in our solar system but 550 light years away in the inconspicuous constellation of Lepus, underneath the bright Orion constellation, an exo-Io could be hidden at the exoplanet system WASP-49b.
The possible exomoon would orbit a hot giant planet, which in turn would race once around its host star in less than three days.
Theoretically, large amounts of sodium at an exoplanet could point to a hidden moon or ring of material, and ten years ago, researchers at Virginia calculated that such a compact system of three bodies: star, close-in giant planet and moon, can be stable over billions of years.