What are comets? – They are often described as huge, dirty, cosmic snowballs. They consist of e.g. from water ice, dry ice – solidified carbon dioxide, admixtures of rocks and dust. They were most likely formed during the formation of the solar system and are its most primal elements. It is believed that the reservoir of comets is the so-called. The Oort cloud, which surrounds the solar system in a huge sphere at a distance of about 100,000 km. astronomical units (1 astronomical unit is the average distance from the earth to the sun). The objects it contains move in unstable orbits, and any gravitational swirl can knock them towards the central regions of the solar system. Such a comet has been traveling towards the Sun for hundreds of thousands of years. When it finally approaches it, the matter contained in its core heats up and sublimates; a head and a comet tail are formed, the researcher says.