11.   Davidsen said that after analyzing those results, it became clear that astronomers had been thinking about the problem in the wrong way.

12.   For decades, astronomers have thought that planets remained stationary after the initial formation of the solar nebula.

13.   It also follows closely the release of classified data suggesting that Earth is hit by smaller strikes more frequently than astronomers thought.

14.   Now some astronomers think they have identified a new class of mysterious and powerful gamma-ray bursts possibly caused by explosions of extremely massive stars called supernovas.

15.   Now, broadening their perspective, astronomers think they are seeing strong evidence of planets forming around young adult stars.

16.   Other astronomers had thought they might be coming from our own cosmic neighborhood, somewhere in the Milky Way galaxy in which the Earth and sun reside.

17.   So astronomers think it must be the result of dark matter particles colliding.

18.   Some astronomers now think they have identified a new class of these gamma-ray bursts.

19.   Some astronomers thought that the intergalactic medium might not exist at all, or might be too tenuous ever to be detected.

20.   The asteroid that made headlines this spring because some astronomers thought it had the potential to hit Earth is about one mile across.