Comet ISON

It may not look like much in this sequence of images taken by NASA's Deep Impact spacecraft from a distance of half a billion miles in January, but the comet identified as C/2012 S1 (ISON) is shaping up to be the most spectacular comet in a generation. If it doesn't break into pieces first, the comet should be among the brightest objects in the sky during the winter of 2013/2014. Video: NASA/JPL-Caltech/UMd (00:25)