What is a Comet: Comet Facts

A comet is a small body in space. It was matter of great interest to astronomers like Sir Edmond Halley. Many decades later, comets still remain a challenging mystery for the field of astronomy. Space research institutes around the world have reported the existence of 3628 comets that are known and studied. Annually, an average of one comet is sighted by the naked eye from the surface of the Earth.

So what exactly is a Comet?

According to the definitions given by the various space research organizations, a comet can be defined as a space body that travels in an elliptical orbit around the sun. Most of the comets travel in elliptical orbits. When the comet comes in the vicinity of the star it is orbiting around, its comma-like tail gets illuminated. A majority of comets are visible only through telescopes and other aids. There are however, some comets which are also visible to the naked eye.

What is a Comet made up of?

A comet is principally made up of ice, dust and different forms of gases. The nature of the components differs from comet to comet. The central part of a comet that looks like a ball is termed as the nucleus. The nucleus is principally made up of ice and frozen gases. The frozen components also include many other compounds like ammonia, methane and carbon dioxide. Rocks are another component of the nucleus. Due to such composition, the nucleus of the comet often resembles a huge ball of dirt and snow.

It is also believed by some astronomers, that the nucleus of a comet is rather fragile because several comets have split into parts without any explainable reason except immense velocity.

The huge elliptical orbit takes the comet in the range of heat of the star around which it is orbiting. When the comet enters the inner parts of the solar system, the frozen content of the nucleus starts melting. The gases and water within the nucleus vaporize as a result of radiation from the star and the solar wind. The immense velocity of the comet and the solar wind, push the vaporized matter away from the nucleus. This gives the comet it's distinct tail and the comma-like appearance. The high amount of heat and the ions (charged particles that are formed due to the heat of the sun) cause the tail of the comet to glow.

How are Comets Formed?

According to their formation or birth, the comets can be classified into two types. The first type is short-term comets which originate in the Kuiper belt as space bodies beyond the orbit of Pluto. The gravitational pull of the planets in the solar system, causes the origin of short term comets. These comets enter the solar system and take the form of active and glowing comets.

Long term comets originate as traveling bodies in the Oort cloud (located around 50,000 light years away from the sun). The gravitational attraction of the planets in the solar system and other gravitational forces cause these comets to form elliptical orbits.

Death of a Comet

The study of comets has revealed that they have a fragile structure. Sometimes, comets split into parts due to sheer velocity. The entry and exit of comets in the solar system in course of its orbit, reduces the amount of matter (ice and frozen gases) in it. Due to this reduction in matter, the comets break-up and disperse into clouds. A dead comet is nothing but an asteroid or a similar form of a space body. Sometimes the comets also crash in other planets when their orbits cross each other. The most famous example of such a comet is the Shoemaker Levy 9, that crashed into Jupiter.

For astronomers who have spent their lives studying comets, it a very heart-breaking moment to gaze at a dying comet. The Halley's Comet is said to be one of the most beautiful comets. Another very beautiful comet is the Hale-Bopp, that was discovered in the year 1995, on 23rd July.

It was predicted by astronomers that the Halley's Comet would be sighted in the November of 1835. Mark Twain, the famous writer, was born just two weeks after the sighting. He developed a very special liking towards the Halley's Comet. In his biography he comments,"I came in with the Halley's Comet, and expect to go with it. The Almighty has said no doubt, Now here are two unaccountable freaks; they came in together; they must go out together." Halley's Comet was next sighted on 20th April, 1910. Twain ended the journey of his life the very next day.

The journey of any comet is indeed like that of Mark Twain. It is remarkably long, fast, adventurous as it streaks across the dark sky.