A new study shows that the Moon has a solid core 500 kilometers in diameter and density similar to that of iron. Its diameter, 3,500 kilometers, is greater than a quarter of Earth's (13,000 kilometers).
If the Earth were the size of a basketball, the Moon would be like a tennis ball and both bodies would be separated by 7 meters apart. The Moon is the most familiar of all celestial objects and the first visited by humans, in short: a star about which we know many details.