List the four main parts of a comet, and identify their physical characteristics?

When the comet approaches to the Sun, it becomes warmer. During this time, several distinct parts are noticeable:

Nucleus is the main and solid part of the comet. Its diameter ranges between 1 to 10 kilometer.

The coma consists of evaporated gas (water vapor, ammonia, carbon dioxide) and dust surrounding the nucleus. It is bigger than the nucleus and together with nucleus they form the head of the comet.

The comet's dust tail is always away from the sun. It is made of small dust particles. The dust tail is easy to see because it reflects sunlight. It is also very long extending several million kilometers.

The second tail called a gas tail. It is also known as the plasma or ion tail. It is made of electrically charged gas molecules (carbon dioxide, nitrogen, water). Depending on the reversion of the Sun's magnetic field sometimes the tail disappears and reappears.