Finding planets? Old hat. What about finding moons?
It seems likely that planets around other stars might also be hosts to their own moons. In addition to just wanting to know what’s out there, detecting exomoons could have implications for the habitability of exoplanets. While gas giants themselves might not be habitable, their potential rocky moons could be, if the planet orbits in the habitable zone. Also, moons can help stabilize a planet’s orbital inclination over long time periods, making it easier for life to maintain its hold rather than experiencing dramatic oscillations in environmental conditions.
This video shows the expected effect that a moon could have on the light curves we observe remotely:
The effect here is quite noticeable because the moon is at high inclination (out of the plane of the planet’s rotation around its star).
HEK (the Hunt for Exomoons with Kepler) is a collaboration established with hopes of finding the first exomoon in Kepler data. They were successful in getting some crowdfunding from PetriDish.org to purchase a supercomputer for their search. Laudably, they plan to post numeric posterior results from their search as an aid to the community.
Exomoons are theorized to tweak the planet’s transit curve in a variety of ways, but they are subtle and in many cases can be confused with other causes (like interactions with other planets in the same system). The community is still working to develop reliable models.
So, no exomoons have yet been found — but it’s probably just a matter of time.