In August of 2007, R Coronae Borealis, or 'R Cor Bor' as we variable star enthusiasts call her, began one of its R CrB-type fading episodes. These fadings are what make R CrB type stars interesting and unique. R CrB is normally a 6th magnitude star, easily observed in binoculars. Occasionally, suddenly and totally unpredictably, the star will fade by as much as eight magnitudes, becoming a faint 14th magnitude star requiring a telescope to observe.
These fading episodes are believed to be caused by the star being dimmed by huge amounts of stellar dust and soot, dredged up from within the star and belched out into its outer atmosphere. Typically, the fading happens rather abrubtly, measured in weeks, and recovery back to maximum light can take several months or a year.
This particular fade has taken on new proportions. Not only has it attained the faintest magnitude in the historical record, it has remained at minimum for longer than ever before also. Some of us are beginning to wonder if the star will ever come back to maximum light again.
Above is the light curve showing the last fifteen years of R CrB activity. Several fading episodes can be seen, but none compares in depth or duration compared to this current fade. The unpredictability and rarity of these type stars makes them favorite targets for variable star observers.
R CrB is heading for solar conjunction. It will be interesting to see what happens when she pops up again in the morning sky. I'll keep you updated.