21.   The complex gravitational tugs of the two stars might preclude the process by which planets form from collapsing clouds of gas and dust, many astronomers thought.

22.   The inner walls are painted battleship gray, which one astronomer thought appropriate.

23.   These Iridium satellites have been reflecting sunlight onto the Earth as they orbit, causing amateur astronomers to think they are viewing exploding stars.

24.   Two weeks ago, the National Aeronautics and Space Administration released pictures taken by the Hubble Space Telescope of what astronomers think are the most distant galaxies ever studied.

25.   Until now, astronomers thought they lacked the techniques to detect small extrasolar planets, but an international research team has proved them wrong.

26.   Until recently, most astronomers thought that the debris trails left behind by a comet spread out and merged together.

27.   Until just three decades ago, astronomers thought that colors changed with the seasons on Mars.

28.   When people come in, they are expecting to see what astronomers think.

29.   With most of the universe being empty space, astronomers once thought the chance of stars colliding was roughly once in an eternity.