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Detached objects are a dynamical class of minor planets in the outer reaches of the Solar System and belong to the broader family of trans-Neptunian objects (TNOs). These objects have orbits whose points of closest approach to the Sun (perihelion) are sufficiently distant from the gravitational influence of Neptune that they are only moderately affected by Neptune and the other planets: this makes them appear to be "detached" from the Solar System.〔 〕〔 D.Jewitt, A.Delsanti ''The Solar System Beyond The Planets'' in ''Solar System Update : Topical and Timely Reviews in Solar System Sciences '', Springer-Praxis Ed., ISBN 3-540-26056-0 (2006) (Preprint of the article (pdf) )〕 In this way, detached objects differ substantially from most other known TNOs, which form a loosely defined set of populations that have been perturbed to varying degrees onto their current orbit by gravitational encounters with the gas giants, predominantly Neptune. Detached objects have larger perihelia than these other TNO populations, including the objects in orbital resonance with Neptune, such as Pluto, the classical Kuiper belt objects in non-resonant orbits such as Makemake, and the scattered disk objects like Eris. Detached objects have also been referred to in the scientific literature as extended scattered disc objects (E-SDO),〔(''Evidence for an Extended Scattered Disk?'' )〕 distant detached objects (DDO),〔 〕 or scattered–extended, as in the formal classification by the Deep Ecliptic Survey.〔 〕 This reflects the dynamical gradation that can exist between the orbital parameters of the scattered disk and the detached population. At least nine such bodies have been securely identified,〔 〕 of which the largest, most distant, and best known is Sedna. Those with perihelia greater than 75 AU are termed sednoids. As of 2014, there are two known sednoids, Sedna and . == Orbits == Detached objects have perihelia much larger than Neptune's aphelion. They often have highly elliptical, very large orbits with semi-major axes of up to a few hundred astronomical units (AU, the radius of Earth's orbit). Such orbits cannot have been created by gravitational scattering by the gas giants (in particular, Neptune). Instead, a number of explanations have been put forward, including an encounter with a passing star or a distant planet-sized object. The classification suggested by the Deep Ecliptic Survey team introduces a formal distinction between ''scattered-near'' objects (which could be scattered by Neptune) and ''scattered-extended'' objects (e.g. 90377 Sedna) using a Tisserand's parameter value of 3.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「detached object」の詳細全文を読む スポンサード リンク
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