The Hunt for Exomoons with Kepler, or HEK, is an astronomy project designed to search for observational evidence of exomoons (extrasolar moons). The exo part of the word simply means the moon lies outside of our own solar system. So far, no-one has ever found an exomoon but there has never been a systematic search for their existence before. HEK will therefore test the hypothesis that moons exist in other solar systems aside from our own.

The Hunt for Exomoons with Kepler (HEK)

Artist’s impression of the view from an exomoon. Image credit: Dan Durda

Why should we care about exomoons? Perhaps, the most fundamental reason is life. Already, astrobiologists believe Europa, Titan and Enceladus (the moons of Jupiter and Saturn) may harbour some form of primitive biology. But what about a true Earth-like world which just happens to be a moon of a larger gas giant? If these habitable moons are possible, then there could even be more habitable moons than habitable planets. Planet-based life could even be a rarity in the Galaxy. HEK cannot tell us whether life inhabits exomoons or not, but the first step is to establish whether moons big enough to support a biosphere exist or not. HEK will hopefully answer this question.

Photo of Jupiter’s moon, Europa, taken by the Galileo spacecraft. The surface is ice and the cracks indicate the surface is young and shifting on an ocean of water beneath. In this ocean, life may reside or have done so in the past.