It appears that Comet Ison has gotten too close to the sun and may have broken up.  Here is a link to the latest as reported by USA today:  http://www.usatoday.com/story/news/nation/2013/11/28/comet-ison-nasa/3776419/

“At this point, I do suspect that the comet has broken up and died,” says Karl Battams, a comet scientist for the Naval Research Laboratory, who joined a NASA and Google+ chat from Kitt Peak Observatory in Arizona. “Let’s at least give it a couple of more hours before we start writing the obituary.”