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，將會有一顆小行星通過月球軌道與地球擦肩而過，這將是一個千載難逢的研究機會。John Matson報道 ，地球將會在11月8日遭遇一顆體積相當大的小行星的“侵擾”，但謝天謝地的是那顆小行星與地球并不那么“親密”。這顆被命名為2005 YU55的小行星將會在325,000 公里外與地球擦肩而過，這比月球近地軌道還低。像這樣近距離的接觸地球的小行星有很多，但這顆卻比較特別，因為它的直徑達到近400米。NASA說這顆小行星有航母那么大，但實際上它卻比航母大的多。上一次像這么大的小行星如此近距離的接近地球還是在1976年，大家都推測這種情況至少要到2028年才會再一次出現。因此這是一次研究這么大小行星的一次千載難逢的機會。科學家屆時將使用位于加利福尼亞州和波多黎各的兩個地球上最大的射電望遠鏡去觀測小行星，并為之繪制雷達圖像。彗星和小行星都保持著行星的基本結構，因此這么近距離的觀測將會為解決地球是怎么形成的這一問題提供直接線索。這么說來像2005 YU55這樣的“訪客”還是非常受歡迎的，前提是它們別太“熱情”了。
—John Matson