Comet
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A comet is an icy, small Solar System body or interstellar object that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitat
Comet Hale–Bopp after passing perihelion in April 1997
Structure of a comet
Comet 81P/Wild exhibits jets on light side and dark side, stark relief, and is dry.
Hubble image of Comet ISON shortly before perihelion.
Oort cloud
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The Oort cloud, sometimes called the Öpik–Oort cloud, is theorized to be a cloud of billions of icy planetesimals surrounding the Sun at distances ranging from 2,000 to 200,000 AU. Its existence was p
Comet
…originate in the Kuiper belt or its associated scattered disc, which lie beyond the orbit of Neptune. Long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the nearest star. Long-period comets are set in motion towards…
The distance from the Oort cloud to the interior of the Solar System, and two of the nearest stars, is measured in astronomical units. The scale is logarithmic: each indicated distance is ten times as far out as the previous distance. The red arrow indicates the projected location, in 2025–2027, of the space probe Voyager 1, which may reach the Oort cloud about 300 years later.
Artist's impression of the Voyager spacecraft
Ceres RC3 Haulani Crater
Pluto in True Color High Res