An Investigation on the Origin of Centaurs’ Color-Inclination Relation

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题名:	An Investigation on the Origin of Centaurs’ Color-Inclination Relation
作者:	劉柏彥;Liu, Po-Yen
贡献者:	天文研究所
关键词:	半人馬小行星;Centaur;inclination;color;KBO
日期:	2018-08-16
上传时间:	2018-08-31 11:33:35 (UTC+8)
出版者:	國立中央大學
摘要:	半人馬小行星的表面顏色之雙峰分佈的起源一直存在著爭論。目前有兩種解釋這種雙峰型顏色分佈的理論:（一）某種能導致半人馬小行星表面性質變化的演化機制;（二）半人馬小行星的起源處便存在著成分之差異。更有趣的是，半人馬小行星可能存在軌道傾斜度和顏色之間的相關性，即藍色(B-R≤1.4)和紅色(B- R>1.4)半人馬小行星分別具有高傾角和低傾角的分佈特徵。在本研究中，我們在上述兩種解釋雙峰型顏色分佈的理論基礎上，提出了兩種可能可解釋顏色與傾角關係的假說。我們考慮:（一）假設正被擾動中的柯伊伯帶天體(SKBOs)原本沒有顏色與傾角的關係,但當他們演化成半人馬小行星且近日點位於土星軌道內時,土星和木星的引力效應可能變得強大到足以大幅改變它們的的傾角,同時,來自太陽的熱輻射也剛好熱到足以引發它們的彗星活動,造成其表面顏色變藍;（二）假設SKBOs也有顏色與傾向的關係(目前還不清楚)，且當它們演化成半人馬小行星時，這一關係在統計上得到了保留。我們對目前觀察到的158個半人馬小行星(其中58個擁有顏色資料)和82個SKBOs進行了數值模擬，以研究它們的動力學演化。我們的研究結果顯示，半人馬小行星的顏色與傾角關係更有可能是從SKBOs繼承而來。我們發現，我們的假說（二）更可能用來解釋半人馬小行星之顏色與傾角的關係。;Since its discovery, there has been a debate on the origin of the bimodal color distribution of Centaurs in the past few decades. In principle, two theories have been proposed to explain this bimodal color distribution: (1) evolutionary processes resulting in changes of the surface properties of Centaurs, and, (2) compositional diﬀerences inherited from the primordial origin of Centaurs. What might be more intriguing is that Centaurs also show a correlation between their orbital inclinations and colors that the blue (B-R≤1.4) and red (B-R>1.4) Centaurs tend to be characterized by high and low inclination distributions, respectively. In this study, we consider two hypotheses to explain the color-inclination relation based on the two major theories of explaining the bimodal color distribution mentioned above. Namely, we consider: (1) Initially, the scattering Kuiper Belt objects (SKBOs) have no color-inclination relation. When they evolve into Centaurs with perihelion distances within Saturn’s orbit, the gravitational eﬀect of Saturn or Jupiter becomes strong enough to greatly change the inclinations of Centaurs. At the same time, the thermal radiation is also strong enough to trigger cometary activities to produce the blue surface colors; (2) Assuming that the SKBOs also have color-inclination relation (which is unclear yet), and this relation is statistically preserved when they evolved into Centaurs. We perform numerical simulations on 158 observed Centaurs (58 of them have color information) and 82 observed SKBOs to investigate their dynamical evolution. Our results show that the color-inclination relation of Centaurs is more likely to inherit from SKBOs. We ﬁnd that our hypothesis (2) is more likely to explain the color-inclination relation of Centaurs.
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