Click on image for full-sized view. Discovered nearly as far out as Jupiter last September, this comet will pass 114 million kilometers from our star and only 56 million km from Earth. As a result this initially very faint comet should brighten considerably, even to the point of becoming a distinct naked-eye object. The prospect of having a fairly bright comet to observe during the summer of 2000 set the Internet abuzz last September. The most optimistic individuals speculated that it would reach 3rd magnitude or even brighter, but any forecast of a comet's peak brightness is fraught with uncertainty.
Many factors influence a comet's luster, the main one being whether it is new or old.
There usually is a significant difference in the way each type performs. The surfaces of new comets are believed to be covered almost completely by a very thin, fragile layer of highly volatile ices intermixed with dust. Rapid outgassing takes place over the entire Sunward surface of the comet, expelling copious amounts of entrapped dust and creating a large, highly reflective coma about the nucleus. The comet looks anomalously bright. However, after a few weeks or months the thin, active mantle is exhausted and the comet's rate of brightening slows dramatically.