Otsukisama ▼

The Moon is Earth's only natural satellite. At about one-quarter the diameter of Earth (comparable to the width of Australia),[15] it is the largest natural satellite in the Solar Systemrelative to the size of its planet,[f] the fifth largest satellite in the Solar System overall, and is larger than any known dwarf planet. Orbiting Earth at an average distance of 384,400 km (238,900 mi),[16]or about 30 times Earth's diameter, its gravitational influence slightly lengthens Earth's day and is the main driver of Earth's tides. The Moon is classified as a planetary-mass object and a differentiated rocky body, and lacks any significant atmosphere, hydrosphere, or magnetic field. Its surface gravity is about one-sixth of Earth's (0.1654 g); Jupiter's moon Io is the only satellite in the Solar System known to have a higher surface gravity and density.  

月です。