University of Virginia, College and Graduate School of Arts and Sciences

Volcanically active exo-moons

September 3, 2019

While our solar system contains dozens of moons orbiting the planets, there is as yet no clear detection of a moon orbiting an extrasolar planet. A group of astronomers and planetary scientists, led by former UVa graduate student Apurva Oza, have a new paper accepted to the Astrophysical Journal ( which shows that these exo-moons may have been hiding in plain sight. Absorption of starlight as it passes by the planet has often been assumed to be due to atoms in the planet’s atmosphere. Oza et al.’s idea is that there may be a volcanic “exo-Io” orbiting the exo-planet which is venting atoms to space which then absorb the starlight. This problem is how these moons may survive the harsh environment near the star. Their calculations find that a handful of known exo-planet systems may be explained by volcanic exo-Io’s. This collaboration was begun in Charlottesville and included a number of current and former UVa/richNRAO people: Oza, Bob Johnson, Carl Schmidt, Chenliang Huang and Arielle Moullet. The paper has recently been discussed in the press at