10

Swift-Tuttle is due back in 2126 (as you know now, it won't hit us) and astronomers think it might become a spectacular naked-eye comet like Hale-Bopp. If historical calculations are correct (see Fact #9) then the 2126 appearance will mark the comet's 3rd millennium of human observation, assuming someone is in fact around to see it.

Editor's note: This information appeared previously on SPACE.com. It has been revised slightly for this year's version of the Perseids. [Viewer's Guide]