英语听力：探索发现 2014-07-09 BBC 地平线：陨石的真相-25（在线收听） |
Luckily, the very biggest asteroids are few and far between. But there are still plenty of rocks out there that represent a significant danger to us. So, at the summit of an extinct Hawaiian volcano, Professor Nick Kaiser and his colleagues are searching the skies for killer asteroids. Every night, using a revolutionary billion-pixel sensor, the team scans a vast swathe of the sky. Follow me up to the next floor, you’ll see a better view of the telescope itself. They are looking for any unidentified objects that could be heading our way. By capturing several images of the same patch of sky, separated by several minutes, the team can see if anything’s changed against the background of stars.
You can see that there’s a dark thing and a white thing. What that means is, in these two exposures, there was an asteroid, which was here in the first exposure and there in the second one. It’s kind of cute. Here’s another one in the same image.
And in fact, we’ll detect hundreds of asteroids in a single exposure. Their observations are collated at the nerve centre of asteroid detection—the Minor Planet Centre, just outside Boston.
Its director is Tim Spahr. And his job is to keep track of every asteroid in the solar system. |
| 原文地址：http://www.tingroom.com/lesson/yytltsfx/2014/273560.html |