Which comets can I see right now?

A comet is a lump of ice and dust a few kilometres across, left over from the birth of the solar system. Far from the Sun it is dark and frozen; as it comes closer, the heat turns its ice into gas that carries dust away, forming a glowing head and tails that can stretch for millions of kilometres. The list below gives, for each comet Perigee follows, an estimated magnitude: the smaller the number, the brighter it is, and only comets below about magnitude 6 can be seen with the naked eye under a dark sky. Comets are famously unpredictable, so these estimates are a guide, not a promise.