Today, we know of more than 5,000 exoplanets: planets outside our solar system that orbit other stars. While the effort to discover new worlds goes on, we’re steadily learning more about the exoplanets we’ve already detected: their sizes, what they’re made of and whether they have atmospheres.
Our team has now provided tentative evidence for a sulphur-rich atmosphere on a world that’s 1.5 times the size of Earth and located 35 light years away. If confirmed, it would be the smallest known exoplanet with an atmosphere. The potential presence of the gases sulphur dioxide (SO₂) and hydrogen sulphide (H₂S) in this atmosphere hint at a molten or volcanic surface.
In our solar system, we have two distinct categories of planets – the small rocky ones, including Earth and Mars, and the gas giants such as Jupiter and Saturn. However, exoplanets span a great spectrum of sizes. Our solar system lacks a planet whose size falls into the range between Earth and Neptune, but it turns out that’s the most common type of planet we have seen around other stars in our galaxy.
