http://www.space.com/scienceastronom...ho_030326.html
space.com says this is one of the "coolest stars ever known", which is hard to dispute - just look at it! (It's the red thing.)
At an estimated 3600F it's less than half the temperature of the sun. But at the same time, it's gotten much brighter. They are trying to figure out why it's behaving the way it is. In a matter of months, it has gotten brighter without getting hotter, and the dust cloud that surrounds it has been expanding in spectacular fashion. They say it isn't a supernova for that reason - a supernova would get way hotter. The link above has a link to an animation that gives us the detail of the expanding dust, and an explanation of light that I don't understand at all.
This must be one of the nicest-looking Hubble images yet. Simply awesome - and a space mystery, to boot.