Do important papers produce high citation counts?

In honor of the centennial of the American Astronomical Society, we asked 53 senior astronomers to select what they thought were the most important papers published in the Astronomical Journal or Astrophysical Journal during this century. This selection of important papers gives us the opportunity to determine whether important papers invariably produce high citation counts. We compared those papers with control papers that appeared immediately before and after the important papers. We found that the important papers published before 1950 produced 11 times as many citations on the average as the controls and after 1950, 5.1 times as many citations. Of the important papers, 92% produced more citations than the average for the control papers. Therefore important papers almost invariably produce many more citations than others, and citation counts are good measures of importance or usefulness. An appraisal of the 53 papers is that three are primarily useful collections of data or descriptions, 46 are fundamental studies giving important results, and four are both useful and fundamental. The lifetimes of all 53 important papers average 2.5 times longer than for the controls. The ages of the authors of these important papers ranged from 23 to 70, with a mean of 39+/-11 years, indicating that astronomers can write important papers at any age.