Exoplanets are being found so frequently now that they have become commonplace. But what about exomoons? As might be expected, they are much harder to detect, being typically much smaller than most planets. There have been tantalizing hints but nothing conclusive so far. That may be about to change soon, however. Astronomers from Columbia University have reported the possible discovery of the first exomoon – but they stress that it is still unconfirmed and just a candidate at this point.