A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail, which is the most distinctive feature of comets.
Comets are composed of dust, ice (frozen water, ammonia, methane, carbon dioxide, and carbon monoxide), and rock. These materials are remnants from the solar nebula, the cloud of gas and dust from which the Solar System formed. The nucleus of a comet can be as small as a few hundred meters to tens of kilometers across.
Comets have been observed since ancient times, often with great fear and superstition due to their unpredictable appearances and dramatic appearance. Notable historical comets include:
In recent years, scientific missions have been sent to study comets up close:
Comets are of great interest to scientists because they are considered to be the most primitive bodies in the Solar System, preserving materials from its early formation. They offer clues about the origin of the Solar System, the formation of planets, and possibly even the delivery of water and organic compounds to Earth, contributing to the development of life.