亚卫星

Also known as moon's moon, moonmoon, submoon

thumb|Artist's concept of exomoon Kepler-1625b I orbiting exoplanet [[Kepler-1625b. Kepler-1625b I could theoretically have a subsatellite itself.|alt=]] A subsatellite, also known as a submoon or informally a moonmoon, is a "moon of a moon" or a hypothetical natural satellite that orbits the moon of a planet.