Bad Astronomy — The fact that ISON is blooming means it’s getting very bright, probably around magnitude 0.5, about as bright as Mercury as seen from Earth. This is expected, and a good sign! It means gas is pouring off the solid nucleus of the comet and being illuminated by the intense light of the Sun. If it manages to hold itself together, ISON will get even brighter over the next day, and the pictures from SOHO will be spectacular.
Don’t forget: I’ll be participating in a NASA Google+ Hangout Thanksgiving day at 18:00 UTC (I’ll be on at 18:30 for an hour), talking about the comet with several scientists, and showing live images from SOHO and other observatories. Stay tuned to the blog and I’ll have the link and an embedded video so you can watch it live. The Planetary Society also has links where you can get more ISON info, and the Comet ISON Observing Campaign is another great source of news.
I plan to post on this tomorrow and throughout the holiday weekend, providing more viewing info in the hope ISON survives the next few days.