Bad news for little princes—there may be fewer Earth-neighboring asteroids for them to live on than thought. According to results released today by NASA's Wide-Field Infrared Survey Explorer mission, an infrared satellite that's been keeping its eye on asteroids zipping within 200 million kilometers of Earth's orbit, there are close to 20,000 near-Earth asteroids between 100 meters and 1 kilometer in diameter  (shown on left). That's down from old guesses of about 35,000 (right). And nearly 15,000 of those rocks, which are big enough to crush an entire city, have yet to be discovered. The researchers also confirmed that astronomers have identified more than 90% of the nearly 1000 big asteroids of the dino-extinction variety. That's too late for Tyrannosaurus rex but perhaps not too late for us.
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