The plethora of moons in our solar system would lead one to think that finding exomoons-i.e. moons in other solar systems-wouldn’t be difficult. In spite of this, however, we haven’t found any. Even the best exomoon candidate so far, Kepler 1625 b-i, is probably something entirely different. If it does exist, it would range in the size from a large rocky planet to Neptune, orbiting a Jupiter-size exoplanet or brown dwarf, and would have formed in one of a number of implausible situations. The data so far is shaky, too, as the low flux that the Kepler Space Telescope has received from the star makes it hard to tell whether the smaller dip in the star’s brightness following the brown dwarf’s dip is the transit of a moon or an anomaly. If it does turn out to be a moon, however, it would look like a mini solar system orbiting another star-an exciting prospect for what is possibly the first exomoon ever detected.
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