Calculations show that the celestial visitor could be dazzlingly bright in November 2013 and be easily visible in broad daylight as it rounds the Sun. Comet ISON is so named because it was first spotted on photos taken by Vitali Nevski and Artyom Novichonok from Russia using the International Scientific Optical Network telescope...
That makes it a type of comet called a sungrazer, and there is a risk that the comet - essentially a giant ball of rock and ice, will break up when it makes that close approach.
But it could become brighter than the greatest comet of the last century, Comet Ikeya-Seki, which excited astronomers in 1965...The article at The Telegraph indicates that this comet should be "fifteen times brighter than the moon."
Comet ISON, which has the official label C/2012 S1, appears to be on a nearly parabolic orbit which leads scientists to believe that it is making its first trip through the Solar System. This means it may have been dislodged from a vast reservoir of icy debris surrounding the Sun far beyond the planets, called the Oort Cloud. It is a giant ball of rock and ice that is likely to be packed with volatiles including water ice that will erupt as brilliant jets of gas and dust when it is at its best.