Scary Asteroids

可怕的小行星

Amateur Astronomer - - 宇宙奥秘 -

Astronomers compile catalogs of all kinds of objects: variable stars, black holes, binary stars, and many others. One of their most important catalogs keeps getting bigger — it passed 15,000 entries a couple of months ago.

天文学家们为所有的天体都编制了目录:变星、黑洞、双星,举不胜举。而他们编制的最重要的一项目录正在不断扩大,在几个月前,这一目录已经超过了15,000条。

The catalog lists N-E-Os — Near-Earth Objects. These asteroids and comets follow paths that approach or cross Earth’s orbit around the Sun. Such objects have the potential to hit our planet, so it’s important to find and track them. With enough warning, it might be possible to deflect an object that’s on a collision course.

这一目录列出了近地小天体(简称NEO)。这些小行星和彗星循着接近或者与地球公转轨道交叉的轨道绕太阳运转。这些天体有可能会撞上我们的地球,所以找到并追踪它们显得尤为重要。通过足够早的警报,改变一个撞向地球的天体的轨道是可能的。

Most of that work is done by automated searches in Arizona and Hawaii, which scan the sky most clear nights of the year. A new search is scheduled to begin next year in Europe, with another, using a giant new telescope in Chile, to follow soon after.

绝大多数的近地天体搜寻工作是通过美国亚利桑那州和夏威夷岛的自动搜寻设备完成的,一年中的大多数晴朗夜晚它们都孜孜不倦地扫描着天空。另一项搜寻工作计划明年开始、在欧洲进行,此后不久,还有一项利用位于智利巨型新望远镜的搜寻工作也会很快加入进来。

Scientists estimate that they’ve found more than 90 percent of NEOs that are at least a kilometer in diameter. Such giant space rocks could cause widespread damage if they hit us. In fact, just such an impact is thought to be responsible for the demise of the dinosaurs.

科学家们估计他们已经发现了90%以上直径至少1千米的近地小天体。一旦它们撞击地球,如此巨大的岩石天体很可能在大范围内引发灾难。实际上,像这样的撞击被认为是恐龙灭绝的原因。

该图绘制了已知对地球具有潜在威胁的1000多颗小行星的运行轨迹。看着密密麻麻的轨迹不禁让人胆战心惊,好在现在还没有发现对地球具有直接威胁的近地小行星。图片来源: NASA,JPL-Caltech

In recent years, searchers have been looking for even smaller objects. Such objects wouldn’t be big enough to trigger global problems if they hit, but they could destroy a city. But smaller objects are also fainter, so it takes much more effort to find them.

近年来,研究者一直在搜寻更小的天体。这类天体一旦撞击地球虽然不太可能引发全球范围的灾难,但是它们可能足以摧毁一座城市。然而,更小的天体也更昏暗,所以要花费更多努力才能找到它们。

So far, the searches haven’t discovered any problems — none of the 15,000 cataloged NEOs is on a threatening course.

到目前为止,经研究尚未发现任何危险近地小天体,目录中的15,000个近地小天体都不在对地球构成威胁的轨道上。

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