First exomoon discovered

NASA's Kepler and Hubble space telescopes have spotted evidence of a Neptune-size satellite orbiting the Jupiter-like planet Kepler-1625b, which lies about 8,000 light-years from Earth,

First Exomoon Found? Neptune-Sized World Possibly Spotted Orbiting Alien Planet

https://www.space.com/42008-first-exomoon-discovery-kepler-1625b.html