Kepler1625b

Kepler-1625b is a gas giant exoplanet candidate discovered by the Kepler Space Telescope, orbiting the star Kepler-1625. The host star is a sun-like star located in the Cygnus region of the Milky Way, several thousand light-years from Earth. Kepler-1625b was identified through transit photometry, with periodic dips in starlight indicating a planet crossing the stellar disk. The planet is characterized as a Jupiter-like gas giant with a relatively long orbital period.

In 2017, an international team reported evidence for a possible natural satellite, designated Kepler-1625b I, orbiting Kepler-1625b. Using the same Kepler light curves, they argued that the transit timing variations and a possible second transit signal could be explained by a Neptune-sized moon. This would make Kepler-1625b I one of the largest known moons.

Subsequent observations and analyses produced mixed results. A March 2018 Hubble Space Telescope follow-up did not confirm the moon's existence, and later reanalysis attributed the signal to data systematics and stochastic noise rather than a moon. As a result, the exomoon detection remains controversial and unconfirmed.

As of now, Kepler-1625b is widely treated as a planet candidate, with the exomoon Kepler-1625b I remaining an unconfirmed candidate and subject to ongoing study.