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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/74055


    Title: 一些X型小行星密度與孔隙度的關係之比較;Intercomparison of the Relations of Density and Porosity of Some X-type Asteroids
    Authors: 朱致萱;Zhu, Zhi-Xuan
    Contributors: 天文研究所
    Keywords: X型小行星;孔隙度;構造
    Date: 2017-07-26
    Issue Date: 2017-10-27 13:06:58 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 小行星的自旋週期極限在探測小行星內部結構時扮演了關鍵角色。直徑大於一公里的小行星,它們的自轉週期不會小於2.2小時,這被稱為「自旋屏障(spin barrier)」,其存在被解釋為小行星是重力束縛的瓦礫堆結構,因此有此自旋週期極限,否則過大的離心力將使小行星崩解。因為不同類型的小行星有不同的體積密度,它們的自旋週期可能不同。我們利用PTF的小行星週期數據庫(Chang et al. 2015, Waszczak et al. 2015)和NEOWISE任務的反照率資料庫(Masiero et al. 2011),來探討X型小行星的自旋屏障,從這個角度來研究小行星的內部結構,其中我們特別關注組成物質為鐵、鎳的M型小行星。我們找到三個各屬於不同化學成份和光譜類型的、自轉速率快的小行星,包括:P型小行星(10305) Grignard、M型小行星(34946) 2286 T-1、E型小行星(10359) 1993 TU36,並假設它們的轉動週期都接近離心力不穩定性條件,以此計算出小行星的體積密度和孔隙度,藉由分析小行星的孔隙度,我們發現E型小行星1993 TU36的內部結構可能發生過重大斷裂事件,P型小行星10305 Grignard和M型小行星 2286 T-1可能為瓦礫堆結構。
    ;The spin-rate limit of asteroids plays a key role in probing the interior structure of asteroids. The 2.2-hour spin-barrier has been interpreted as a result of the “rubble-pile” structure of asteroids (i.e., gravitationally bounded aggregations). Because asteroids of different types should have different bulk densities, their spin-rate limits could be different. We use the asteroid rotation periods of the PTF project (Chang et al. 2015, Waszczak et al. 2015) and the NEOWISE albedos (Masiero et al.2011; Mainzer et al. 2011) to study the spin-rate limits of X-type asteroids. In this way, we can study their bulk densities, which in turn probes asteroid interior structure. We are particularly interested in the M-type asteroid, which is mainly made of nickel-iron. We found three fast rotating asteroids classified to different chemical compositions and spectrum types: P-type asteroid, (10305) Grignard;M-type asteroid, (34946) 2286 T-1;E-type asteroid, (10359) 1993 TU36. If their gravitational force and centrifugal force were in balance, we found that E-type asteroid, (10359) 1993 TU36, was probably heavily fractured; P-type asteroid, (10305) Grignard and M-type asteroid, (34946) 2286 T-1, were probably rubble-pile structure.
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