海王星外天體(Trans-Neptunian Objects, TNOs)不止保存了太陽系原始組成，而 且記錄了外太陽系的碰撞演化資訊。然而，已經被發現的小海王星外天體的數量 非常有限，仍然需要大視場大口徑的望遠鏡來偵測他們。 在這項研究裡，我們使用Hyper Suprime-Cam Subaru Strategic Program(HSC- SSP)的深視場資料來做分析。這項計劃從2014年一直持續到2019年，主要利用 裝設在口徑8.2米Subaru望遠鏡上，擁有1.77平方度視野的Hyper Suprime-Cam相 機。我們總共找到43顆候選天體，視星等分布從21.97到25.42等(等同於直徑80- 520公里)，其中39顆(74%)是新發現的天體。藉由延伸每一顆候選天體的移動軌 跡，我們取得它們的精確的軌道參數，並且測量了其中至少32顆TNO跟1顆半 人馬座小行星(Centaur)的表面顏色。我們發現到這些TNO的顏色分佈雖然散佈 非常廣，但是仍然符合前人觀測到的紅化趨勢。由於我們發現的天體數量並不 多，我們並沒有觀測到顏色與軌道參數(半長軸、曲率、傾角)有相關性。除此 之外，在這些新發現的天體裡，有蠻大的比例(40%)都有很大的亮度變化(小於 等於0.4個星等)。對比於以前的研究，我們沒有發現光變大小與絕對亮度有相關 性，這可能是因為我們每天只有一兩個小時的觀測資料，所以並沒有涵蓋整個旋 轉週期，因此低估了亮度變化的大小。;Trans-Neptunian Objects (TNOs) hold the pristine and critical information not only on the composition but also on the collisional evolution of the outer Solar System. However, information for these small and faint TNOs is still limited as observations require telescopes with large aperture and wide field of view. In this study, we utilized the data obtained from the HSC-SSP survey Deep and Ul- tradeep layers, which uses the 8.2m aperture of the Subaru Telescope and 1.77 deg field-of-view of the Hyper Suprime-Cam, from 2014 to 2019. We present 43 candi- date detections, in which 39 (74%) are new discoveries, with magnitude of 21.97 ? 25.42 mag and sizes of about 80 ? 520 km in diameter. By extending each of the object’s observation arc, we were able to place an accurate measurement of orbital properties and a very good estimate of colors to at least 32 of our TNO candidates and 1 centaur candidate. The intrinsic faintness and seeing-transparency varia- tion during observations primarily constrained us from recovering the remaining 10 detected objects. We found that the color of our remaining TNO candidates is dispersed in a large range but is consistent with the observed reddening trend. However, because of this small sample size, we did not see any correlation of the TNO colors with orbital parameters (semimajor axis, eccentricity, and inclination). Additionally, we find that a large fraction (40%) of our TNO candidates exhibit a large brightness variation of ?m ? 0.40 mag. In contrary to earlier studies, we did not find a correlation between the light curve amplitude and absolute magnitude probably because we did not cover the whole rotation period of the TNOs due to short data span (1-2 hr) in our observations.
