2019年10月18日:来自星际空间的博里索夫彗星-（Interstellar Interloper 2I/Borisov）

2019年10月18日:来自星际空间的博里索夫彗星-（Interstellar Interloper 2I/Borisov）--原图下载

Image Credit: NASA, ESA, and D.Jewitt (UCLA)et al.

说明: 自2017年侦测到斥候星（1I/'Oumuamua）之后，博里索夫彗星（2I/Borisov）成为第二颗确认来自星际空间的访客。就像斥候星，博里索夫彗星的双曲线轨迹和掉向太阳的速率，让我们得以确认它是源自太阳系外头的天体。不过详细的观测指出，石质的斥候星和现知太阳系天体有不少的差异，然而来自深空的博里索夫彗星，则是颗不折不扣的彗星。这幅2019年10月12日，由哈伯太空望远镜拍摄的博里索夫彗星影像，显示它具有我们很熟悉的彗星活动，彗核的周围也聚集着尘埃。虽然这张影像并未解析出彗核，但据估计彗核的直径介于2到16公里之间。在哈伯取像之时，博里索夫彗星的距离大约有4亿1千8百万公里远。博里索夫彗星仍在靠近之中，将在12月7日，运行到距离约3亿公里（2天文单位）的最近太阳位置。

原文：

Image Credit: NASA, ESA, and D.Jewitt (UCLA)et al.

Explanation: After the 2017 detecton of 1I/'Oumuamua,comet2I/Borisov has becomethe second recognized interstellar interloper.Like 'Oumuamua, Borisov's measured hyperbolic trajectory and speed asit falls toward the Sun confirm that its origin is frombeyond our Solar System.But while detailed observations indicate'Oumuamua is a rocky bodywith differences from known Solar System objects,Borisov is definitely a far wandering comet.Taken on October 12, 2019 thisHubble Space Telescope image of Borisovreveals a familiar looking comet-like activityand concentration of dust around around its nucleus.Not resolved in the image, some estimates suggest the nucleus could bebetween 2 and 16 kilometers in diameter.At the time of the Hubble image,comet 2I/Borisov was about 418 million kilometers away.Borisov is still inbound though and will make its closest approachto the Sun on December 7 ata distance of about 300 million kilometers (2 Astronomical units).