Oort cloud: see comet comet [Gr.,=longhaired], a small celestial body consisting mostly of dust and gases that moves in an elongated elliptical or nearly parabolic orbit around the sun. Comets visible from the earth can be seen for periods ranging from a few days to several months.
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Oort cloud

Vast spherical cloud of small, icy bodies orbiting the Sun at distances ranging from about 0.3 light-year to one light-year or more that is probably the source of most long-period comets. In 1950 the Dutch astronomer Jan Hendrik Oort (1900–92) noted that no comets have orbits that would indicate an interstellar origin. He proposed that the Sun is surrounded by billions of these objects, which are only occasionally detectable when they enter the inner solar system. The Oort cloud is believed to be composed of primordial bodies dating from the formation of the solar system (see solar nebula). Whether the Oort cloud merges, in its inner region, into the disk-shaped Kuiper belt is not known.

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No references found	The Oort Cloud is a remnant of the nebula from which the solar system formed 4. Earth's mass extinctions not likely caused by crashing comets by Asian News International For the past 25 years, the inner Oort Cloud has been considered a mysterious, unobserved region of the solar system capable of providing bursts of bodies that occasionally wipe out life on Earth," said study author Nathan Kaib. Comets probably won't cause the end of life as we know it: study by AFP / AFP American Edition For the past 25 years, the inner Oort Cloud has been considered a mysterious, unobserved region of the solar system capable of providing bursts of bodies that occasionally wipe out life on Earth," said study author Nathan Kaib. Comets probably won't cause the end of life as we know it: study by AFP / AFP Global Edition	Oogonium ookinete oolemma oolicast oolicastic porosity Oolite oolith oolitic chert oolitic limestone oology oomicrite oomicrudite Oomycetes Oomycetidae Oomycota OOO OOoFf OOP oophagous oophoritis OOPL ooplasm OOPS OOPSLA OORDBMS Oort cloud Oort dark matter Oort's Cloud Oort, Jan Hendrik OOSD OOSE oospararenite oosparite oosparrudite Oospore Oost, Jacob van oostegite Oostende Oosting, Henry J. OOT Ootacamund ootype oovoid OOXML ooze OP op amp Op Art op code opa Opa-Locka	OOPUJ OOQ OOQAM OOR OORA Oorah OOram OORASS OORB OORC OORDBMS OORDBMS OORF OORG Oorial Oorlogsgravenstichting Oorlogsvrijwilliger OORM OORMIC OORMS OORP OORPC OORPT OORR Oort Oort Oort Oort cloud Oort Cloud Object Oort dark matter Oort's Cloud Oort, Jan Hendrik Oort, Jan Hendrik OORTC OORTS OORTSF OOS OOSA OOSAD Oosaka Oosaka OOSB OOSBT OOSC OOSC2 ooscopy OOSD OOSD OOSDP OOSE OOSE OOSE OoSec OOSEDOP OOSEP OOSFR OOSH

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The Oort Cloud is a remnant of the nebula from which the solar system formed 4.

Earth's mass extinctions not likely caused by crashing comets by Asian News International

For the past 25 years, the inner Oort Cloud has been considered a mysterious, unobserved region of the solar system capable of providing bursts of bodies that occasionally wipe out life on Earth," said study author Nathan Kaib.

Comets probably won't cause the end of life as we know it: study by AFP / AFP American Edition

Comets probably won't cause the end of life as we know it: study by AFP / AFP Global Edition