"In 2018, astronomers discovered what could be an exomoon, estimated to be the size of Neptune. It was found in orbit around a gigantic gas planet 8,000 light-years from Earth. But the scientists behind this discovery, hesitant to confirm that the new find is an exomoon due to some of its peculiarities, say more observation is needed. Their findings were published in the journal Science Advances.
https://edition.cnn.com/2019/07/17/w...rnd/index.html