An "outburst" occurs when a new area on the surface of the nucleus becomes active. Comets are generally rather fragile objects, and they tend to
fragment and break apart over time. When this happens, fresh ices are exposed to the Sun, and these ices start sublimating (changing from a solid
directly to a gas). The overall result is an increase in brightness, because there is more material in the coma to reflect sunlight.
On a side note, I still haven't seen this comet. I became aware of the "outburst" the day after it had occurred (when the skies were clear), and
since then it has been cloudy
[edit on 30-10-2006 by Mogget]
[edit on 30-10-2006 by Mogget]