An exomoon circles a gas giant planet in this artist's impression. What happens to exomoons when their planets interact? Rogue moons, torn from their planets and flung outward to drift through space, may be as common as stars in the universe, a new study finds. Moons are common in the solar system, with Jupiter alone possessing at least 67. As such, Yu-Cian Hong, an astrophysicist at Cornell University, wanted to see how moons around distant stars might behave, she said.