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The Oort cloud (/ ɔːr t, ʊər t /), [1] sometimes called the Öpik–Oort cloud, [2] is theorized to be a vast cloud of icy planetesimals surrounding the Sun at distances ranging from 2,000 to 200,000 AU (0.03 to 3.2 light-years). [3] [note 1] [4] The concept of such a cloud was proposed in 1950 by the Dutch astronomer Jan Oort, in whose ...
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The Oort cloud is thought to be composed of comets that were ejected from the inner Solar System by gravitational interactions with the outer planets. Oort cloud objects move very slowly, and can be perturbed by infrequent events, such as collisions, the gravitational effects of a passing star, or the galactic tide , the tidal force exerted by ...
Numerous such comets have been observed when close to the Sun. The closer an object is to the Sun the faster it needs to move to maintain the orbit. Objects move slowest when furthest from the Sun (aphelion) and fastest when closest to the Sun (perihelion) and this is why Oort cloud comets spend most of their time in the Oort cloud.
This is a list of parabolic and hyperbolic comets in the Solar System.Many of these comets may come from the Oort cloud, or perhaps even have interstellar origin. The Oort Cloud is not gravitationally attracted enough to the Sun to form into a fairly thin disk, like the inner Solar System.
C/2014 UN 271 came from the Oort cloud and has been inside of the orbit of Neptune (29.9 AU) since March 2014 and passed inside the orbit of Uranus (18.3 AU) in September 2022. [k] [16] [40] The time of perihelion has been well-known since June 2021. [6] The current 3-sigma uncertainty in the comet's distance from the Sun is ±35,000 km. [16]
The existence of planets beyond Neptune, ranging from less than an Earth mass up to a brown dwarf has been often postulated [37] [38] for different theoretical reasons to explain several observed or speculated features of the Kuiper belt and the Oort cloud.
So far, it appears that rather than a sudden drop in the amount of comets orbiting the sun at about 50,000 AU, the Oort cloud rather uniformly decreases in size, the further away from the Sun it goes. As current observations indicate, the Oort limit is somewhere around 50,000 AU (0.8 LY) from the Sun.