類彗星軌道小行星是一種不同於一般主帶小行星的天體，它們擁有類似彗星的軌道特徵，以相當的橢圓軌道繞太陽公轉，並與木星軌道重疊。受到木星重力場影響，這類小天體穩定存在於軌道的時間尺度平均僅4.5×107年（Levison & Duncan, 1997），關於這類天體的存在，我們可以理解成軌道演化過程中的一個暫時態（transient state），因此，它們的來源與未來演化，也就成了一個有趣的課題。 在本文中，我使用鹿林一米望遠鏡來進行可見光的觀測工作，取得類彗星軌道小行星的顏色與光度變化資料，來分析它們的顏色分佈趨勢，比對先前文獻，尋找是否和已知類型的小天體聚落（如彗星核心、半人馬座天體、特洛依小行星）有任何關聯性。另外我也利用現有的軟體套件，對觀測目標做軌道演化的模擬計算。 在近一年的觀測裡，共取得了41個類彗星軌道小行星的顏色資訊，4個自轉光變曲線，並且發現了一個新的間歇性活躍天體—212P。初步的成果顯示，所觀測的41個小行星，由於亮度已接近一米望遠鏡的測光極限，光度誤差相當大，其顏色分佈趨勢相當疏散，需要累積更多的觀測資料，才足以判定它們真正的分佈狀況。在軌道演化的模擬計算中，我發現從現有的軌道參數，無法直接判斷一個天體是否存在於不穩定的類彗星軌道，在41個觀測目標中，僅四成天體的運行軌道在十萬年間會有顯著改變。 未來我將以這兩年的研究方法與成果為基底，與即將上線觀測的泛星計畫（Pan-STARRs）合作，使用龐大的移動天體資料庫（Moving Object Processing System, MOPS）來進行更精確、更大量的分析判斷，以探索太陽系小天體的演化史。 Asteroids in Cometary Orbits (ACOs) belong to an unusual type of asteroids with large orbital eccentricity. The planet-crossing orbit will decrease the stability of their current orbit at a mean timescale of 4.5×107 years (Levison & Duncan, 1997). We can regard the ACOs as a transient state of the small body evolution, therefore it is an interesting topic to discuss the origin and evolution of ACOs. In this work, I used the Lulin One-meter Telescope (LOT) to do the optical observation to get the color and light-curve of ACOs. To trace their origin, we compared our observation data to other asteroid groups which types are already known like the cometary nuclei, Centaur objects, and Trojan asteroids to find any possible relation. In addition, I also looked backward into the history of ACOs via orbital simulation with the Mercury package. I got the color information of 41 ACOs, and rotation curves of 4 ACOs, and find a new quasi-active comet in last year. Limited by the aperture of LOT, the photometry accuracy is not enough for me. The preliminary result shows there has no significant trend of color distribution. We need more observations and ACO data to confirm whether they really have some possible relation between physical parameters and color. The result of orbital simulation shows that the current orbital parameters are not a good criterion to select the ACOs. Only 40% of my targets have clearly changed their orbital parameters in the past 100,000 years. I plan to use the Pan-STARRS database to improve my current research in the future. The Moving Object Processing System (MOPS) can provide an extremely large photometry and astrometry data for analyzing the detail of ACOs.
