Although the beauty of comets is unsurpassable, they are merely giant balls of frozen water. Yes, that's right, comets are blocks of frozen ice mixed with cosmic dust. There is also a small percentage of ammonia, methane, and CO2. They are described as snowballs(frozen ice) that have become dirtied by the dirt(cosmic dust) that is washed up by the cars going by.These chunks are theorized to have originated from the forming of giant planets like Saturn, Jupiter, Neptune, and Uranus, and each comet is usually the size of one of the Rocky Mountains. There are four parts to a comet: nucleus, coma, plasma tail, and dust tail. The nucleus is the only permanent part of the comet. Although it has never been seen, there is no doubt of its existence. The brightness of the comet can depend on how large the nucleus' diameter is since these spherical forms can scatter sunlight like a mirror.
Image: CometImage Source: Views of the Solar Sytem
Comets are created all the time. There is an estimated trillion comets on the edge of the solar system. Yet, visibility of comets is very susceptible to light pollution, and because of the growing population and pollution, fewer and fewer comets are being seen.Image: CometImage Credit: Comet
When the comet passes close to the sun, it changes from a solid state to a gaseous one because of the intense heat. When this happens, it releases gas and dust, which forms more or less a circle around it. This is when the comet becomes more visible. The coma absorbs more light than it reflects, but it still reflects a small percentage of it.. The coma tends to blend in with the tail because some of the gas is mixed in with the tail debris. The plasma tail is a tail of ions. This tail only appears separate from the dust tail if its direction is perpendicular to the orbit of the comet's plane, otherwise, it will blend in with the dust tail. The dust tail is the most stunning and beautiful of the comet, often being striped with different colors from different types of gases. The dust tail always faces the opposite direction of the sun because of the exerts a repelling force. The dust tail is nothing more than gases, particles, and cosmic dust that is forced back from the coma from the repelling force, but still held in by the pull of the nucleus, creating an amazing thing to see across the sky. Most comets do not pass Neptune, but some slip past and venture in closer to the Earth's pull. When it comes closer to the sun is when the dust tail forms, and gets pulled in close for a good look. The dust tail can sometimes be up to 100 kilometers long.