For anyone not following along, the story of Comet ISON has become infinitely more interesting over the past few days.
Wednesday, as ISON approached the Sun, astronomers began to report a sudden decrease in brightness. It was starting to look like ISON had either shed much of its outer ice layers, and so had less ice to blast off into space, or the nucleus had disrupted and released a large amount of dust which was obscuring the nucleus. This is apparently common for small “sungrazing” comets, as the heat and tidal forces involved in a close approach with the Sun are intense, and comets are not the most ridged of structures.
Thursday, as ISON was seen to approach the Sun from the SOHO spacecraft, it appeared that the comets coma had disappeared. The coma is the region surrounding the nucleus. It’s a compact, mostly spherical region of icy gas and dust that makes up the comet’s “head”. ISON appeared to be little more than a tail, with the “bright” region stretched out over the inner region of said tail. This is a hallmark signature of a destroyed comet. It looked like the party was over, especially when the first images of ISON after its closest approach to the Sun were very faint and wispy.
ISON appeared to be gone.
Today? Not so much. Time lapse images from the SOHO spacecraft show a small ball of fuzz appearing out from behind the making plate the spacecraft uses to block the direct light from the Sun (SOHO studies the region surrounding the Sun). It didn’t appear to be much, but it was more than we saw last yesterday. As the frames tick past, the fuzzy patch brightens, forms a ball, and grows a pair of tails!
We have no idea the scope of the damage done to ISON. What once promised to be a spectacular December viewing experience may yet be over before it ever began, if ISON has been significantly depleted by its encounter with the Sun. If, on the other hand, the bulk of the nucleus has remained in tact, the comet could just as easily outburst in the coming days and weeks, and become a grand fixture on our skies into early January.
If nothing else, a whole slew of new photographs of ISON should start appearing on the web as early as Sunday night.