Introducing Comet ISON . ... Credit Copyright: Ligustri Rolando Explanation: Could this dim spot brighten into one of the brightest comets ever? ... Sky enthusiasts the world over are all abuzz, though, from the more optimistic speculations -- that the newly discovered C/2012 S1 (ISON) could develop a spectacular tail or briefly approach the brightness of the full Moon toward the end of 2013. Comet ISON currently is very faint but is just visible at magnitude 18 in the above image. ...