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A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing.This produces an extended, gravitationally unbound atmosphere or coma surrounding the nucleus, and sometimes a tail of gas and dust gas blown out from the coma.
Periodic comets (also known as short-period comets) are comets with orbital periods of less than 200 years or that have been observed during more than a single perihelion passage [1] (e.g. 153P/Ikeya–Zhang). "Periodic comet" is also sometimes used to mean any comet with a periodic orbit, even if greater than 200 years.
C/ indicates a non-periodic comet i.e. any comet that is not periodic according to the preceding definition. X/ indicates a comet for which no reliable orbit could be calculated (generally, historical comets). D/ indicates a periodic comet that has disappeared, broken up, or been lost. [5]
Periodic comets usually have elongated elliptical orbits, and usually return to the vicinity of the Sun after a number of decades. The official names of non-periodic comets begin with a "C"; the names of periodic comets begin with "P" or a number followed by "P". Comets that have been lost or disappeared have names with a "D". Comets whose ...
This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields.Astronomy is concerned with the study of celestial objects and phenomena that originate outside the atmosphere of Earth.
The following list is of comets with very long orbital periods, defined as between 200 and 1000 years.These comets come from the Kuiper belt and scattered disk, beyond the orbit of Pluto, with possible origins in the Oort cloud for many.
A famous 'wow!' sign that has long been attributed to aliens may finally have a scientific explanation.
As the comet warms, parts of it sublimate; [1] this gives a comet a diffuse appearance when viewed through telescopes and distinguishes it from stars. The word coma comes from the Greek κόμη (kómē), which means "hair" and is the origin of the word comet itself. [2] [3] The coma is generally made of ice and comet dust. [1]