Comet ISON, formally known as C/2012 S1, was discovered a little more than a year ago. 
Even then, astronomers recognized that it had the potential to become the "comet of
the century," owing to the fact that it was due to come well within a million miles 
(1.6 million kilometers) of the sun. If comets survive that kind of close encounter,
they can become dramatically brighter � which means ISON is the star of a real
cliffhanger: Will it hold together and live up to its potential, or will it break 
apart before it has a chance to hit prime time?