RT Journal Article SR Electronic T1 Evidence for a large exomoon orbiting Kepler-1625b JF Science Advances JO Sci Adv FD American Association for the Advancement of Science SP eaav1784 DO 10.1126/sciadv.aav1784 VO 4 IS 10 A1 Teachey, Alex A1 Kipping, David M. YR 2018 UL http://advances.sciencemag.org/content/4/10/eaav1784.abstract AB Exomoons are the natural satellites of planets orbiting stars outside our solar system, of which there are currently no confirmed examples. We present new observations of a candidate exomoon associated with Kepler-1625b using the Hubble Space Telescope to validate or refute the moon’s presence. We find evidence in favor of the moon hypothesis, based on timing deviations and a flux decrement from the star consistent with a large transiting exomoon. Self-consistent photodynamical modeling suggests that the planet is likely several Jupiter masses, while the exomoon has a mass and radius similar to Neptune. Since our inference is dominated by a single but highly precise Hubble epoch, we advocate for future monitoring of the system to check model predictions and confirm repetition of the moon-like signal.