cometes

Comets are small bodies of the Solar System composed of ice, dust and rocky material. They originate in the outer regions of the Solar System and become visibly active when they approach the Sun, releasing gas and dust that forms a surrounding coma and often one or more tails that point away from the Sun.

The solid nucleus is typically a few kilometers in diameter and is surrounded by the coma, which can extend tens of thousands of kilometers. The two main types of tail are the dust tail, created by solar radiation reflecting sunlight and dragging dust away, and the ion or plasma tail, formed by solar wind interactions and typically bluish in appearance.

Orbits: Most comets come from two distant reservoirs: the Kuiper Belt beyond Neptune and the Oort Cloud, a distant nearly spherical shell. Short-period comets have orbital periods under about 200 years and often originate from the Kuiper Belt; long-period comets from the Oort Cloud have highly elongated orbits. Some comets are Halley-type with periods of 20–200 years.

Observation and exploration: Comets have been observed since ancient times. In the modern era, detailed observations come from telescopes and spacecraft flybys and rendezvous. Notable examples include Halley's Comet (1P/Halley), Comet Hale-Bopp (C/1995 O1), Comet Hyakutake (C/1996 B2), and 67P/Churyumov-Gerasimenko studied by the Rosetta mission. Missions such as Deep Impact and Stardust provided insights into composition and dust grains. Comet activity can also influence meteor showers when Earth crosses debris trails.

Science and culture: Comets are studied for clues about the early Solar System and the delivery of water and organic molecules to Earth. Throughout history, comets have appeared in cultural contexts as symbols and omens in various traditions.