The Search for Exomoons

Now that more than 400 exoplanets have been discovered, focus has moved from finding planets to characterise these alien worlds. As well as detecting the atmospheres of these exoplanets, part of the characterisation process undoubtedly involves the search for extrasolar moons.

We review some of the proposed detection techniques and introduce a model for the TTV and TDV signals which permits not only the identification of exomoons but also the derivation of some of their characteristics.

The detectability of a habitable-zone exomoon around various configurations of exoplanetary systems with the Kepler Mission or photometry of approximately equal quality is investigated. We calculate both the predicted transit timing signal amplitudes and the estimated uncertainty on such measurements in order to calculate the confidence in detecting such bodies across a broad spectrum of orbital arrangements. The effects of photon noise, stellar variability and instrument noise are all accounted for in the analysis. We validate our methodology by simulating synthetic lightcurves and we find that habitable-zone exomoons down to 0.2 Earth masses may be detected and ∼ 25,000 stars could be surveyed for habitable-zone exomoons within Kepler‘s field-of-view.