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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 ...
Artist's rendering of the Kuiper belt and Oort cloud. Freeman Dyson proposed that trans-Neptunian objects, rather than planets, are the major potential habitat of life in space. [citation needed] Several hundred billion to trillion comet-like ice-rich bodies exist outside the orbit of Neptune, in the Kuiper belt and Inner and Outer Oort cloud.
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.
The classic Oort cloud theory states that the Oort cloud, a sphere measuring about 50,000 AU (0.24 pc) in radius, formed at the same time as the solar nebula and occasionally releases comets into the inner Solar System as a giant planet or star passes nearby and causes gravitational disruptions. [44]
The asteroid and comet belts orbit the Sun from the inner rocky planets into outer parts of the Solar System, interstellar space. [16] [17] [18] An astronomical unit, or AU, is the distance from Earth to the Sun, which is approximately 150 billion meters (93 million miles). [19]
Description 134340 Pluto: A dwarf planet, the first and largest trans-Neptunian object (TNO) discovered. It is the only TNO known to have an atmosphere. Hosts a system of five satellites and is the prototype plutino. 15760 Albion: The prototype classical Kuiper belt object (KBO), the first TNO discovered after Pluto (385185) 1993 RO
Figure 1: Geometry of the Oort constants derivation, with a field star close to the Sun in the midplane of the Galaxy. Consider a star in the midplane of the Galactic disk with Galactic longitude at a distance from the Sun. Assume that both the star and the Sun have circular orbits around the center of the Galaxy at radii of and from the Galactic Center and rotational velocities of and ...
Simulations indicate that it has most likely come from the Oort cloud, with a roughly equal probability of being an extinct comet and a rocky body that was originally scattered into the Oort cloud. The discovery of 1996 PW prompted theoretical research that suggests that roughly 1 to 2 percent of the Oort cloud objects are rocky. [2] [10]