cometeiden

Cometeiden is a term used in astronomy to refer to the celestial bodies known as comets. Comets are icy, small solar system bodies that, when passing close to the Sun, display a visible atmosphere or coma, and sometimes also a tail. These phenomena are a result of the ice in the comet's nucleus sublimating, or turning directly into gas, as it is heated by solar radiation. The sublimated gas and dust then form a glowing cloud around the nucleus, and the solar wind and radiation pressure can push this material away from the nucleus, forming a tail that always points away from the Sun.

The composition of comets is primarily ice, such as water, carbon dioxide, and ammonia, mixed with dust and rock particles. They are often described as "dirty snowballs." Comets originate from the outer regions of the solar system, primarily the Kuiper Belt and the Oort Cloud. Their orbits are typically highly elliptical, meaning they spend most of their time far from the Sun and then make brief excursions into the inner solar system.

When a comet enters the inner solar system, it can become visible from Earth. Some comets orbit the Sun repeatedly, while others are on one-time trajectories that will eventually send them out of the solar system. The study of comets provides valuable insights into the early conditions of the solar system, as they are thought to be remnants from its formation. They are also a source of water and organic molecules that may have played a role in the origin of life on Earth.