Hubble may have spotted the first known exomoon
Dubbed ‘Neptmoon,’ the gas moon’s unusually large size defies theories on how moons form
![Neptomoon](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2018/10/100218_LG_exomoon_feat.jpg?fit=860%2C460&ssl=1)
SIDE BY SIDE A Jupiter-sized planet and a Neptune-sized moon cross in front of the star Kepler 1625 in this artist’s illustration. Hubble spotted signs of the moon in observations made in October 2017.
Dan Durda