Surprise! Amateur Astronomers Report a Comet Outburst
Sky & Telescope said:
Remember Comet Holmes? In 2007 it exploded from practically nothing to become a weird, slowly expanding, glowing ball easily visible to the naked eye for several weeks. It brightened by about 14.2 magnitudes: half a million times.
Now something similar, though less dramatic, has happened to Comet C/2012 X1 (LINEAR) in the pre-dawn sky. It has flared up by 6 magnitudes, or 250 times, to reach magnitude 8.