The main part of the comet is the solid core. Its diameter is usually from 1 to 10 km. The core consists of ice, frozen gases and solid particles of some other substances.
As the comet approaches the Sun, the core heats up, and its substances begin to evaporate. A gas shell forms around the core, and then a long tail appears. The tail of a comet can stretch for millions of kilometers! It is always directed away from the Sun and consists of gases and fine dust. When a comet moves away from the Sun, its tail and gas shell gradually disappear.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.