11.   Astronomers believe we may be seeing a galaxy similar to our own Milky Way when it was a squalling infant.

12.   Before the Explorer was launched, astronomers had long believed the interstellar dust and gas filling all galaxies would prove impenetrable to instruments operating at extreme ultraviolet wavelengths.

13.   A few astronomers believe the blackness is merely a shadow.

14.   But planetary astronomers believe that the comet may have been pulled into thousands of small chunks besides the big ones.

15.   But some astronomers believe that the havoc, evident even to amateur stargazers with back-yard telescopes, may be only skin deep.

16.   Chandra was designed to operate for at least five years, though some astronomers believe its lifetime could be double that.

17.   Many astronomers believe that light pollution from such a bright satellite would interfere with observations.

18.   Most astronomers believe a black hole exists at the heart of the Milky Way.

19.   Most astronomers believe such a large planet can only have formed much farther out, and spiraled in.

20.   Most astronomers now believe that quasars, the most violently energetic and bright objects known in the universe, are young black holes devouring stars at a furious rate.