Exomoons

Astronomers have found thousands of planets orbiting other stars. Now they're on the cusp of discovering their moons too

- Giles Sparrow

In early April, NASA's James Webb Space Telescope completed its third observing programme, a nine-month-long roster of research proposed by astronomers around the world. Among the many groundbreaking projects in the infrared telescope's packed schedule was the most ambitious attempt so far to track down an entirely new class of alien world.

Exomoons, as the name suggests, are satellites of exoplanets. These worlds are tantalising for several reasons. Their discovery could tell us more about how planetary systems form and they could open up new ways to study the properties of their parent planets. Most intriguingly, they could vastly increase the number of potentially habitable worlds suitable for life to evolve.