Apart from the pulsar planets--the first easily seen exo-worlds were "Hot Jupiters" very close to their respective stars--where that hammer-throw wobble was really evident. So you'd know the first exo-moon detected would have to be a whopper, right? Here you go: https://www.mnn.com/earth-matters/s...have-been-discovered-outside-our-solar-system Now for years, I have had my hopes up that liquid water--and maybe life--might be on a moon like Europa circling a gas giant closer in, say--to a brighter star (maybe 47 Ursae Majoris?) I always thought that a gas giant larger than Jupiter might have a moon--oh, I don't know--Mars size. I never got my hopes up that any Earth sized moon could exist. And here is something the size of...Neptune. More than I could ever hope for. Whoof!
In terms of relative sizes, it reminds me of the Earth/Moon combo. At least in our solar system, our moon is relatively large compared to its planet.
And another "nearby world" https://www.universetoday.com/13683...system-another-possible-exoplanet-discovered/