地球有史以来第二位星际访客要来了

我们有史以来第二位星际访客现在有了一个名字：2i/鲍里索夫

An interstellar comet on its way to visit us has been officially named after the amateur astronomer who discovered it.

一颗即将造访我们的星际彗星以发现它的业余天文学家的名字正式命名。

2I/Borisov was previously known as C/2019 Q4 Borisov. The 'I' stands for 'interstellar' and the '2' because it's only the second ever seen, behind 2017's 1I/'Oumuamua.

2I/Borisov以前被称为C/2019 Q4 Borisov。“I”代表“星际”，“2”代表这是继2017年的“1I/ Oumuamua”之后第二次被看到。

Its recognition as an interstellar object is no surprise, with its distant origins obvious within days after Ukrainian skywatcher Gennady Borisov saw it in August on his home-made telescope.

它被确认为一颗星际物体并不令人意外，在乌克兰天文观测者根纳季·鲍里索夫(Gennady Borisov)今年8月用自制望远镜观测到它几天后，它的遥远起源就显而易见了。

"After a week of observations by amateur and professional astronomers all over the world, the Minor Planet Center was able to compute a preliminary orbit, which suggested this object was interstellar," the International Astronomical Union said.

国际天文联合会说：“经过全世界业余和专业天文学家一周的观测，小行星中心能够计算出一个初步轨道，这表明这个天体是星际天体。”

"The orbit is now sufficiently well-known, and the object is unambiguously interstellar in origin; it has received its final designation as the second interstellar object, 2I. In this case, the IAU has decided to follow the tradition of naming cometary objects after their discoverers, so the object has been named 2I/Borisov."

“现在，这个轨道已经足够为人所知，而这个物体的起源也很明确，是星际的;它最终被指定为第二个星际物体，2I。在这种情况下，国际天文学联合会决定遵循以发现者的名字命名彗星物体的传统，所以这个物体被命名为2I/Borisov。”

Its orbit is hyperbolic, meaning it has enough speed to escape the sun's gravitational pull. Its origins are unknown, but a paper by Polish astronomers suggests it may have been flung at us by a binary star, Kruger 60, 13 light-years away.

它的轨道是双曲线，这意味着它有足够的速度逃脱太阳的引力。它的起源尚不清楚，但波兰天文学家的一篇论文表明，它可能是由13光年外的克鲁格60双星向我们抛出的。

"When searching for a home system of an interstellar body one should look for a past close proximity at a very small relative velocity of order of just a few kilometres per second," they wrote.

他们写道:“在寻找星际体的家园系统时，我们应该寻找过去非常接近的天体，其相对速度非常小，只有每秒几公里。”

"We found that a double-star Kruger 60 is a good candidate for a home system of this comet."

“我们发现双星克鲁格60是这颗彗星家庭系统的一个很好的候选者。”

Unlike 'Oumuamua, which was only seen on its way out, Borisov is yet to arrive. It'll make its closest approach to the sun on December 7, about twice the distance from Earth to the sun.

与“Oumuamua”不同的是，鲍里索夫还没有抵达。它将在12月7日最接近太阳，大约是地球到太阳距离的两倍。

It'll be easiest to spot from Earth in December and January, but only from the southern hemisphere, according to space.com. It's not known whether it'll be visible to the naked eye, but is already starting to form a tail.

据space.com网站称，在12月和1月从地球上最容易观测到它，但仅限于南半球。目前还不知道它是否能用肉眼看到，但它已经开始形成尾巴。

Its size is estimated at a few kilometres across, and its speed at 150,000km/h.

据估计，它的直径只有几公里，速度为每小时15万公里。