Comets are unsteady body,
which usually include little not many kilometers in distance. When you are at a
great distance from the Sun are down, its small core, which can vary from a few
hundred meters to about 10 km. only reflects light. Near the sun the core is
surrounded by a "head", the comma, whose diameter can be up to 30,000
km. The coma is composed of gas emerged from the nucleus by sublimation and
dust. Its production increases severely as we advance the Sun.
