A coronal mass ejection was captured in the image above by the STEREO-A spacecraft. This blast of particles from the sun can be seen on the right. Comet ISON is on the left, and scientists are unsure whether the coronal mass ejection took the sungrazing comet out.
Karl Battams, an astrophysicist and computational scientist based at the Naval Research Laboratory in Washington DC, notes that "molecular emission from the comet has fallen dramatically, meanwhile dust production seems to be enormous. What this could indicate is that the nucleus has completely disrupted, releasing an enormous volume of dust while significantly reducing emission rates. Fragmentation or disruption of the nucleus has always been the highest risk factor for this comet so if this has indeed happened then while unfortunate, it would not be a surprise."
However, Battams says that we still need to keep observing the comet to be sure what is happening. After all, Battams reminds us, "the last time we saw an object like this was never! Furthermore, a sungrazing comet just three days from perihelion has never been studied in this kind of detail - we're breaking new ground here! When we factor in your standard "comets are unpredictable" disclaimer, what we have is a huge recipe for the unknown."