On November 8th an asteroid will pass Earth within the moon's orbit, offering a rare opportunity for study. John Matson reports On November 8th, Earth will have a close encounter with a sizable asteroid. But not too close, thankfully. The asteroid, designated 2005 YU55, will pass Earth at a distance of about 325,000 kilometers, just inside the orbit of the moon. Asteroids come that close frequently, but 2005 YU55 is notable for its dimensions: 400 meters in diameter. NASA says the asteroid is the size of an aircraft carrier, but it's actually even larger. The last time an asteroid this big came this close to Earth was 1976, and it looks like it won't happen again until 2028. So astronomers are taking the rare opportunity to study a hefty asteroid without having to send a craft into deep space. Scientists will use two of the largest radio telescopes on the planet, one in California and one in Puerto Rico, to make radar images of the asteroid. Comets and asteroids preserve the building blocks of the planets. And studying them up close provides clues to how planet Earth came to be. So visitors such as 2005 YU55 are welcome—as long as they keep a respectful distance. —John Matson

11月8日，将会有一颗小行星通过月球轨道与地球擦肩而过，这将是一个千载难逢的研究机会。John Matson报道 ，地球将会在11月8日遭遇一颗体积相当大的小行星的“侵扰”，但谢天谢地的是那颗小行星与地球并不那么“亲密”。这颗被命名为2005 YU55的小行星将会在325,000 公里外与地球擦肩而过，这比月球近地轨道还低。像这样近距离的接触地球的小行星有很多，但这颗却比较特别，因为它的直径达到近400米。NASA说这颗小行星有航母那么大，但实际上它却比航母大的多。上一次像这么大的小行星如此近距离的接近地球还是在1976年，大家都推测这种情况至少要到2028年才会再一次出现。因此这是一次研究这么大小行星的一次千载难逢的机会。科学家届时将使用位于加利福尼亚州和波多黎各的两个地球上最大的射电望远镜去观测小行星，并为之绘制雷达图像。彗星和小行星都保持着行星的基本结构，因此这么近距离的观测将会为解决地球是怎么形成的这一问题提供直接线索。这么说来像2005 YU55这样的“访客”还是非常受欢迎的，前提是它们别太“热情”了。
—John Matson