Pre-discovery Activity of New Interstellar Comet 2I/Borisov beyond 5 au
Pre-discovery Activity of New Interstellar Comet 2I/Borisov beyond 5 au
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新星际彗星 2I/鲍里索夫 5 天文单位以外的预发现活动
DOI：
10.3847/1538-3881/ab659b
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
Roger M. Smith
中科院分区：
文献类型：
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作者：
Q. Ye 叶;M. Kelley;B. Bolin;D. Bodewits;D. Farnocchia;F. Masci;K. Meech;M. Micheli;R. Weryk;E. Bellm;E. Christensen;R. Dekany;A. Delacroix;M. Graham;S. Kulkarni;R. Laher;B. Rusholme;Roger M. Smith
彗星2i/鲍里索夫是2019年8月在距离太阳不远的∼3Au发现的第一颗明确的星际彗星。目前还没有超过3Au的发现前探测到的报告，这主要是因为从地球上看，这颗彗星离太阳很近。在这里，我们介绍了使用Catalina Sky Survey、泛STARRS和兹维基瞬变设施(ZTF)拍摄的图像搜索鲍里索夫彗星发现前的探测，并在Bolin等人中介绍了进一步的全面后续活动。我们在2019年5月拍摄的ZTF图像中确认了鲍里索夫彗星，并使用这些数据更新了它的轨道。这使我们能够在2018年12月获取的图像中识别出这颗彗星，当时它距离太阳7.8Au。这颗彗星在2018年11月没有被探测到，当时它距离太阳8.6Au，可能意味着大约在这个时候开始了活动。这表明，彗星的活动要么是由H2O以外的更易挥发的物质驱动的，如CO或CO2，要么是由无定形冰的放热结晶驱动的。我们在2018年11月使用未检测到的数据推导出原子核的半径为<；7公里，并估计在2018年12月至2019年9月期间一直活跃的面积为∼0.5，尽管这个数字与型号有关，并且高度不确定。鲍里索夫彗星在进站过程中的行为与在太阳系观测到的动态新彗星一致，这表明两者之间有一些相似之处。
Comet 2I/Borisov, the first unambiguous interstellar comet ever found, was discovered in 2019 August at ∼3 au from the Sun on its inbound leg. No pre-discovery detection beyond 3 au has yet been reported, mostly due to the comet’s proximity to the Sun as seen from the Earth. Here we present a search for pre-discovery detections of comet Borisov using images taken by the Catalina Sky Survey, Pan-STARRS, and the Zwicky Transient Facility (ZTF), with a further comprehensive follow-up campaign being presented in Bolin et al. We identified comet Borisov in ZTF images taken in 2019 May and use these data to update its orbit. This allowed us to identify the comet in images acquired as far back as 2018 December, when it was 7.8 au from the Sun. The comet was not detected in 2018 November when it was 8.6 au from the Sun, possibly implying an onset of activity around this time. This suggests that the activity of the comet is either driven by a more volatile species other than H2O, such as CO or CO2, or by exothermic crystallization of amorphous ice. We derive the radius of the nucleus to be <7 km using the non-detection in 2018 November, and estimate an area of ∼0.5– has been active between 2018 December and 2019 September, though this number is model-dependent and is highly uncertain. The behavior of comet Borisov during its inbound leg is observationally consistent with dynamically new comets observed in our solar system, suggesting some similarities between the two.