Astronomy Picture of the Day——星际访客2I/Borisov彗星

Interstellar Interloper 2I/Borisov 
Image Credit: NASA, ESA, and D. Jewitt (UCLA) et al.

Explanation: After the 2017 detecton of Oumuamua, comet 2I/Borisov has become the second recognized interstellar interloper. Like 'Oumuamua, Borisov's measured hyperbolic trajectory and speed as it falls toward the Sun confirm that its origin is from beyond our Solar System. But while detailed observations indicate 'Oumuamua is a rocky body with differences from known Solar System objects, Borisov is definitely a far wandering comet. Taken on October 12, 2019 this Hubble Space Telescope image of Borisovreveals a familiar looking comet-like activity and concentration of dust around around its nucleus. Not resolved in the image, some estimates suggest the nucleus could be between 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 approach to the Sun on December 7 at a distance of about 300 million kilometers (2 Astronomical units).

星际访客2I/Borisov彗星

继2017年探测到奥陌陌之后，2I/Borisov彗星成为第二个被确认的星际访客。和奥陌陌一样，Borisov彗星在落向太阳时所测量到的双曲线轨迹和速度证实了它来源于我们的太阳系之外。然而，详细的观测表明奥陌陌是一个岩石星体，与已知的太阳系天体不同，而Borisov绝对是一颗遥远的流浪彗星。这幅由哈勃太空望远镜拍摄于2019年10月12日的Borisov彗星影像呈现了一种熟悉的类似彗星的活动，以及其核心周围的尘埃浓度。据估计，这颗彗核的直径可能在2到16公里之间。在哈勃望远镜拍摄这幅影像时，2I/Borisov彗星距离我们约4.18亿公里。Borisov彗星仍在靠近之中，将在12月7日到达近日点，距离太阳约3亿公里（2个天文单位）。

高清原图地址：

https://apod.nasa.gov/apod/image/1910/STSCI-H-p1953b_1106.jpg

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