INTRODUCTION

OCTOBER 5, 2018 BY EVAN GOUGH
First Exomoon Found! A Neptune-Sized Moon Orbiting a Jupiter-Sized Planet

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.”

With Thanks to the Space Telescope Sience Institute

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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

Articles on Exomoons

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Hubble site article on exomoons

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CAN MOONS HAVE MOONS?
Juna A. Kollmeier1 & Sean N. Raymond2
Draft version October 9, 2018 (PDF)