via NASA Comet ISON Observing Campaign
We've never made any secret of the unpredictability of comets, or of comet ISON, and the dramatic events of last week simply served to underline that. Here's a quick recap for those that are late to the party...
Just over a week ago, around November 10th or 11th, comet C/2012 S1 (ISON) was simply a reasonably bright magnitude +8 object visible to observers with small telescopes or perhaps binoculars in dark sky regions. All this changed, however, around November 13th when ISON very abruptly and dramatically begin to flare up in brightness. Within four days it suddenly became a spectacular object, naked eye visible to observers with very dark skies and easily visible to urban observers with binoculars or telescopes.
The reason for this flare-up remains unknown. It could simply be the result of increased activity as it enters the inner solar system and has to deal with increasing amounts of solar radiation. It could also have fragmented. All of these are within the realms of the possible outcomes that we have talked about extensively on this site.
For now, all we can do is wait and observe, though time is running out fast for the latter. Comet ISON now shines as a 4th magnitude object but ground observations are limited to an increasingly brief window just before dawn. The moon is also interfering with observations, making it harder to get reliable photometric data, and it's not going to get any easier at this point.
continue reading http://isoncampaign.org/Present