FINDING AND DEFINING EXOMOONS

As our catalogue of exoplanets grows, the hunt is on for moons around distant worlds

- Robert Lea

Astronomers may have finally discovered a moon orbiting around a planet outside our Solar System. The development could have important implications for our understanding of how planetary systems evolve, as well as indicating how typical the planets of our Solar System are. Since the first discovery of planets around stars other than the Sun was made in the early 1990s, our catalogue of planets outside the Solar System has burgeoned, now containing over 4,000 confirmed worlds. One of the most important aspects of our investigation of these extrasolar planets – or exoplanets – is the assessment of how similar or diverse they are in comparison to the planets of the Solar System.

It’s unsurprising given how Earth’s own Moon has dominated our imagination and played a vital role in both astronomy and humanity’s exploration of space that the hunt for moons around these extrasolar worlds – or exomoons – is a subject of intense interest. This is compounded by the fact that moons are abundant in the Solar System, with an average of 20 moons for each planet. And we have no reason to believe that our planetary system is unique in this respect, making the elusive nature of exomoons confusing and frustrating.