List of exomoon candidates



, there have been no positive confirmations of satellites of extra-solar planets (exomoons); however, some evidence in favour of their existence has been produced.

Timeline

 * — It has been surmised that J1407b, a possibly planetary-mass object that eclipsed the star V1400 Centauri in 2007, may have a few moons based on gaps observed in its circumstellar disk or ring system. Later studies have since found that J1407b is most likely a free-floating sub-brown dwarf or rogue planet, possibly less than 6 Jupiter masses.
 * — The confirmed extrasolar planet WASP-12b may also possess a moon.
 * , —  — candidate exomoon of a free-floating planet MOA-2011-BLG-262, was announced, but due to degeneracies in the modelling of the microlensing event, the observations can also be explained as a Neptune-mass planet orbiting a low-mass red dwarf, a scenario the authors consider to be more likely.
 * — researchers using the Hubble Space Telescope published observations of the candidate exomoon Kepler-1625b I, which suggest that the host planet is likely several Jupiter masses, while the exomoon may have a mass and radius similar to Neptune. The study concluded that the exomoon hypothesis is the simplest and best explanation for the available observations, though warned that it is difficult to assign a precise probability to its existence and nature.
 * — reanalysis 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 and Wiegert's conclusion was more and higher quality transit timing data would be required to establish whether these are truly moons or not. 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.
 * — astronomers reported an habitable-zone 1.7 Earth radius exomoon candidate transiting one of the components in the planetary-mass binary 2MASS J1119-1137AB.
 * — 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 the Sun, it too could be within the habitable zone. However, this candidate is based on limited observations (only two transits) and some consider the data to be non-convincing.
 * — 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 would be terrestrial-mass, ranging from 0.76 Lunar masses to 0.34 Earth masses depending on the planet's mass and moon's orbital period.
 * — a follow-up study by the same team found that the observed TTVs are caused by a second planet in the system, and not by a moon.
 * — The exomoon candidate around Kepler-1625b was again challenged, along with the Kepler-1708b candidate. This study argues that the statistical significance of these exomoon candidates is lower than previously claimed (with false positive probabilities of 10.9% and 1.6%, respectively) and that true giant exomoons would have stronger evidence. Evidence for exomoon transits may be caused by stellar activity in the Kepler light curves. Kipping's team published a response arguing that these exomoon candidates remain possible.