One of the brightest comets of the past five years will likely reach its peak brightness this week. Comet Ikeya-Zhang, officially known as C/2002 C1, can now be seen without aide from a dark location above the western horizon shortly after sunset.

In the last week, Comet Ikeya-Zhang has become bright enough to be just visible to the unaided eye. Based on its present activity, observers are optimistic that Ikeya-Zhang will become substantially brighter. This composite...