NASA Stereo: ISON Comet approaching the Sun - video

Now that we have observations of the comet in the NASA STEREO instruments and, more recently, the ESA/NASA SOHO LASCO C3 instrument, CIOC team member Matthew Knight has been able to start recording photometry of the comet.

His results seem to imply that the comet may have experienced an outburst during the (approximate) period Nov 21 - 23 with corresponding brightness increase, followed by a leveling off and then dropping back down to "pre-outburst" levels.

Since entering the LASCO C3 field of view, comet ISON has increased by at least a factor of four, and indications are it may be closer to a factor of ten. In the most recently available images, the comet appears to be around magnitude +0.5.

It is now the opinion of the CIOC Team that Comet ISON is now behaving like a sungrazing comet. We can not comment on whether the nucleus is in tact or not, but our analyses indicate that its rate of brightening is directly in line with that we have experienced with other sungrazing comets.

This has no implication on its chances of survival. We strongly encourage all professional solar observatories who have plans in place for observing the comet, to please do so, and the teams should plan for an object brighter than negative one magnitude (and we are being conservative on this estimate).

Today's tl;dr is somewhat upbeat: we don't know if ISON will survive, and we won't know until it either does it or vaporizes but the comet is still "alive" and brightening dramatically in accordance with the behaviour we expect of sungrazers. Professional observers with solar telescopes should plan for a negative magnitude object, and we urge observation from these facilities.