It's a free, community project Comets are thought to be small pieces of debris left over from the formation of the solar system . A comet consists of a nucleus, which is a small body, similar to an asteroid , but mostly made up of water ice, CO-ice and dust. When the nucleus get close to the sun , the ices start to evaporate, dragging some of the dust with them. The coma and the tails shine because of reflected solar radiation and heated gas emitting its own radiation.
Most comets are too faint to be visible without the aid of a telescope .
A few each year become bright enough to be visible with the naked eye. Before the invention of the telescope, comets seemed to appear out of nowhere in the sky and gradually vanish out of sight. They were usually considered bad omens of deaths of kings or noble men, or coming catastrophes. From ancient sources, such as Chinese oracle bones, it is known that there appearance have been noticed by humans for millenia. It was not settled whether comets are atmospheric phenomena or interplanetary objects until the 16th century, when Tycho Brahe measured that they must be outside of the Earth's atmosphere.