1.   But now another very similar possibly-threatening asteroid has been discovered.

2.   For the fifth time in two years, astronomers have discovered an asteroid hurtling through space that might collide with the Earth.

3.   Now, another very similar, possibly threatening, asteroid has been discovered.

4.   Orbit calculations are very difficult to make from the sparse data gathered since the asteroid was discovered less than three months ago, he said.

5.   Suppose, for example, a new asteroid is discovered.

6.   A new camera hoisted atop a Hawaiian volcano has discovered asteroids that could pass exceedingly close to Earth, the Jet Propulsion Laboratory announced here Wednesday.