A pair of astronomers combing through data from the Kepler spacecraft have discovered the first exomoon. The moon is in the Kepler 1625 system about 8,000 light years away, in the constellation Cygnus. It orbits the gas giant Kepler 1625b, and, unlike all the moons in our Solar System, this one is a “gas moon.”
This diagram shows the sequence of photometric observations taken by Hubble. The purple object represents the planet Kepler 1625b, and the smaller green object is that planet’s exomoon. The exomoon travels in front of the star about 3.5 hours after the planet. Image: NASA, ESA, D. Kipping (Columbia University), and A. Feild (STScI)
Neptune’s largest Moon, Triton. Astronomers think that Triton is a captured Kuiper Belt Object. Credit: NASA/JPL
Hubble site article on exomoons
CAN MOONS HAVE MOONS?
Juna A. Kollmeier1 & Sean N. Raymond2
Draft version October 9, 2018 (PDF)