for the available observations, though warned that it is difficult to assign a precise probability to its existence and nature. However, a reanalysis of the data published in April 2019 concluded that the data was fit better by a planet-only model. According to this study, the discrepancy was an artifact of the data reduction, and Kepler-1625b I likely does not exist. A paper by Chris Fox and Paul Wiegert examined the Kepler dataset for indications of exomoons solely from transit timing variations. Eight candidate signals were found that were consistent with an exomoon, however the signals could also be explained by the presence of another planet. Fox & Wiegert's conclusion was more and higher quality transit timing data would be required to establish whether these are truly moons or not. However, in August 2020 David Kipping re-derived the timings of six of the eight targets (based on a pre-peer review version) and evaluated the TTV evidence as uncompelling. The same study finds that Kepler-1625b I remains an exomoon candidate. In August 2021, astronomers reported an habitable-zone 1.7 exomoon candidate transiting one of the components in the planetary-mass binary 2MASS J1119-1137AB. In January 2022, an exomoon candidate was reported around the planet Kepler-1708b, and because it is orbiting a planet at approximately 1.6 AU from a star that is slightly more luminous than our Sun, it too could be within the habitable zone. However, this candidate is based on limited observations (only 2 transits) and some consider the data to be non-convincing. In November 2022, another exomoon candidate was reported around the planet Kepler-1513b (KOI-3678.01). Unlike the previous giant exomoon candidates of Kepler-1625 and Kepler-1708, this exomoon is terrestrial-mass, ranging from 0.76 Lunar masses to 0.34 Earth masses depending on the planet's mass and moon's orbital period. List Detection projects As part of the Kepler mission, the Hunt for Exomoons with Kepler (HEK) project is intended to detect exomoons. Habitability Habitability of exomoons has been considered in at least two studies published in peer-reviewed journals. René Heller & Rory Barnes considered stellar and planetary illumination on moons as well as the effect of eclipses on their orbit-averaged surface illumination. They also considered tidal heating as a threat for their habitability. In Sect. 4 in their paper, they introduce a new concept to define the habitable orbits of moons. Referring to the concept of the circumstellar habitable zone for planets, they define