The cold water areas beyond Pluto are the regions of comets. During the early stage of solar system, when the sun was just ignited, its heat took lighter elements to the outer solar system. Hydrogen, oxygen and carbon collected into snow cotton like balls that float like a cloud. Comets are made of 'ices', ie ordinary water mixed with frozen gases such as methane, CO2 and ammonia.
Comets move slowly in the enormous orbits around the sun. Comets do not shine while they are in the cloud. When the gravity of a passing star disturbs this cloud, comets are lost into the solar system. As comets move towards the sun, due to heat the frozen ice turns into gas forming a rapidly glowing cloud called its head or coma around its centre.
As it gets closer to the sun, the gas evaporates making its head bigger and brighter. A tail made of dust and gas is pushed out by the pressure of sunlight and solar wind. The tail will be away from the sun. When it passes very close, it gets enormous speeds and the tail points ahead.