Comets are basically packs of ice, made of water and gas, and dust orbiting stars at high speeds. What is strange about these celestial objects is that they did not form any planets during the early parts of their lives while the solar system was forming. This queer aspect makes them an interesting specimen to study if one is interested in the early universe.
The comets in our solar system, such as Comet Halley, usually have very long orbits and spend most of this time away from the sun. During these periods, comets appear to be just simple heaps of rock, dust and ice traveling through the cosmos. But when a comet is traveling towards and near the sun, it has several clear parts: the nucleus, coma, hydrogen cloud, dust tail and ion tail. The nucleus is a mostly solid, stable core composed of ice, gas, dust and some other solids. The coma is the part of the comet in which the water, carbon dioxide and other gases have sublimed, or turned from a solid phase directly to a gaseous phase. The Hydrogen cloud is a giant envelope of hydrogen gas surrounding the comet. The dust tail is the very prominent feature of the comet that can be seen with the unaided eye. This tail can often be millions of kilometers long and is made up of small sized dust particles driven off the nucleus by the escaping gas. The ion tail is even longer than the dust tail, often as much as 100 million kilometers in length. This tail is made of plasma and other effects created by the comet's interaction with the solar wind.

As said before, many comets in our solar system often have huge orbits; some even exceed the orbit of Pluto. But as they make their return trip to the sun, they begin to encounter more and more solar wind. But what is solar wind? The sun does not only emit vast amounts of heat and energy, it emits large amounts of protons and electrons: charged particles. These particles, when emitted in large quantities and at high speeds have the power to affect many things. This solar wind is known to cause beautiful events such as Aurora Borealis but also causes unwanted effects like power surges.
Due to their size and speed, comets have the power to severely damage anything in their path. The chances of any comet impacting the planets in our solar system are greatly increased because the comet's orbit often intersects the orbits of other planets, and many close encounters have been recorded. Comets are amazing objects and continue to fascinate many people today.