"The first exomoons that we find will be large – maybe Mars- or even Earth-sized – and therefore intrinsically more likely to be habitable than small moons," said René Heller, at the Leibniz Institute for Astrophysics in Potsdam, Germany. "With Kepler finding many more giant planets than terrestrial planets in stellar habitable zones, it's really important that we try to figure out what conditions might be like on the moons of these giants to gauge if they can host extraterrestrial life."
In a series of papers published in 2013, Heller and his colleague Rory Barnes from the University of Washington and the NASA Astrobiology Institute tackled some of the big-picture problems to habitability posed by the relationship between exomoons and their host planets. Heller and Barnes have proposed a circumplanetary "habitable edge," similar to the well-established circumstellar "habitable zone." This zone is the temperature band around a star within which water neither boils off or freezes away on a planet's surface – not too hot, not too cold, thus earning it the nickname "the Goldilocks zone.
This past July, 2017 reports New Scientist, evidence emerged of the first discovery of a moon around a planet beyond our solar system that might prove Heller's 2013 prediction above correct. Although the exomoon’s existence has yet to be confirmed, new results from Kepler Data show that the world may look stranger than anyone thought and may also have been created through some unknown mechanism.
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