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121Oort cloud — An artist s rendering of the Oort cloud and the Kuiper belt (inset). Sizes of individual objects have been exaggerated for visibility …
122Orbital resonance — For the science fiction novel by John Barnes, see Orbital Resonance (novel). In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their… …
123Orbit — This article is about orbits in celestial mechanics, due to gravity. For other uses, see Orbit (disambiguation). A satellite orbiting the Earth has a tangential velocity and an inward acceleration …
124Parallax — For other uses, see Parallax (disambiguation). A simplified illustration of the parallax of an object against a distant background due to a perspective shift. When viewed from Viewpoint A , the object appears to be in front of the blue square.… …
125Planets beyond Neptune — Planet X redirects here. For the Planet X doomsday scenario, see Nibiru collision. For other uses, see Planet X (disambiguation). Trans Neptunian planets redirects here. For dwarf planets and small bodies discovered beyond Neptune, see Trans… …
126Population inversion — In physics, specifically statistical mechanics, a population inversion occurs when a system (such as a group of atoms or molecules) exists in state with more members in an excited state than in lower energy states. The concept is of fundamental… …
127Star — For other uses, see Star (disambiguation) …
128Solar System — This article is about the Sun and its planetary system. For other systems, see planetary system and star system. For a list of physical and orbital statistics for the Solar System s largest bodies, see List of gravitationally rounded objects of… …
