Moons

A moon is characterised by the fact that it orbits a planet. Apart from Mercury and Venus, all the planets in our Solar System have at least one moon, with Jupiter and Saturn even have more than 60 each. Some interesting scientific examples are described under the links on the right. Researchers assume that there are also extrasolar moons, or exomoons for short, just as there are planets outside our Solar System - so-called exoplanets. To date, however, the existence of an exomoon has not been proven beyond doubt.

How a moon is created

There are different ways in which a moon can be created. Once a planet has formed, leftover dust clusters around it and can form a moon. Or gravity causes an asteroid to enter the orbit of the planet, and it then orbits it as a moon. Scientists suspect that Jupiter and Saturn have a particularly large number of moons because their mass has "captured" many asteroids. If a moon is formed in the manner described above, it is quite small in relation to the planet. The diameter of the Earth's moon is almost a quarter of the Earth's diameter and is therefore unusually large. Scientists therefore explain its development through a different mechanism. The proto-Earth collided with another protoplanet, called Theia. The proto-Moon, which gradually took on its present mass and position, was formed during this collision.