Comets and The Kuiper Belt
Comets are a big rock of ice and silicates. These usually hang out in the Kuiper Belt but when they complete their orbit, in which they get close to the sun, is when their ice starts to evaporate due to the temperatures in which the ice cannot be to stay solid. This is apparent in our planets that of which the terrestrial planets are made of silicates and the gas giants are made of gas because of the cold temperatures which allow for such gas to form. This is where the comets are formed. There is such a thing called the Kuiper belt where there are small rocks that did not get used in the formation of the solar system, either got caught in the orbit of the sun, not used, or the gas giants prevented them to have gravitational forces great enough to form into something. These comets, however, formed in the Oort cloud which contains the Kuiper belt. This makes sense in a way because where would new ones come from? There is a satellite launched on Jan. 9th, 2006 in which took a photo of Pluto on July 14, 2015 which is believed to be close to the Oort cloud. This could mean a big discovery in this decade and/or a good explanation.