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(47171) 1999 TC36
(also written: (47171) 1999 TC36) is a system comprising three trans-Neptunian objects (TNOs). It was discovered in 1999, by Eric P. Rubenstein and Louis-Gregory Strolger during an observing run at Kitt Peak National Observatory (KPNO). Dr. Rubenstein was searching images taken by Dr. Strolger as part of the Low-Z Supernova Search program. It is classified as a plutino with a 2:3 mean-motion resonance with Neptune, and, currently only being 30.5 AU from the Sun, is among the brighter TNOs. It reached perihelion in July 2015.
==Physical characteristics==
is a triple system consisting of a central primary, which is itself a binary, and a small moon (component B).〔 The combined observations by the infrared Spitzer Space Telescope, Herschel Space Telescope and the Hubble Space Telescope (HST) make it possible to estimate the sizes of the components and consequently provide the range of possible values for the objects’ bulk density. The single-body diameter (effective system size) of is currently estimated at .〔
The very low estimated density of 0.3–0.8 g/cm3 obtained in 2006 (when the system was thought to be a binary) would require an unusually high porosity of 50–75%, assuming an equal mixture of rock and ice.〔 The direct measurement of visible fluxes of all three components of the system in 2009 by the HST has resulted in an improved average density of confirming the earlier conclusion that the object is probably a rubble pile.〔 The density was revised up to in 2012 when new information from the Herschel became available. For a bulk density in the range 1–2 g/cm3 the porosity is in the range 36–68%, again confirming that the object is a rubble pile.〔
has a very red spectral slope in visible light and a flat spectrum in near infrared. There is also a weak absorption feature near the wavelength of 2 μm, probably caused by water ice. The best model reproducing the near infrared spectrum includes tholins, crystalline water ice, and serpentine as surface materials. These results are for the integrated spectrum of all three components of the system.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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