Astronomers ranging from the professional level down to the amateur sky watcher are all disappointed with comet ISON. The comet had the potential to be the brightest in hundreds of years and was called the comet of the century by some. Unfortunately, the comet didn't make it around the sun intact. NASA says that the investigation into exactly what happened to ISON and what remains is ongoing.
However, the US space agency believes that ISON is nothing but a ball of dust at this point. NASA says that it hopes to determine if the "bright stream" that remains is merely a ball of dust left over from the comet's destruction or if a small fragment of the comet nucleus remains.
NASA wrote is a statement:
There's no doubt that the comet shrank in size considerably as it rounded the sun, and there's no doubt that something made it out on the other side to shoot back into space. The question remains as to whether the bright spot seen moving away from the sun was simply debris, or whether a small nucleus of the original ball of ice was still there.
Melting away behind the sun was the least desirable fate for the comet, which began its trek towards our solar system and the sun from the Oort Cloud about 3 million years ago. The reason that the team is still investigating what happened to the comet when so many scientific instruments were turned on it is due to the nature of the images delivered by the NASA Solar Terrestrial Relations Observatory and the ESA/NASA solar and Heliospheric Observatory.
Those two instruments are designed to look directly at the sun and deliver images known as Coronagraphs. Those images, like the one above, block out the sun to give a better image of dim structures in the atmosphere of the sun. Since the sun was blocked out, when ISON entered the area, it too was blocked out leaving it unviewed. When the comet disappeared, scientists believed that it had meted in the sun's heat until the object emerged from the other side of the sun. Scientist hope that the Hubble space telescope will be able to make better observations later in December.