Comets, Awesome Celestial Objects

Comets are nebulous celestial bodies orbiting the sun. A comet is characterized by a long, white tail, but only in the segment of the orbit of the comet when it happens on the next sun.

Comets are often unaware of other components of the solar system by their appearance rather nebulous and extremely elongated orbits.
Composition

A comet is usually consist of as a small, hot core embedded in a nebulous disk called a coma. American astronomer Fred L. Whipple in 1949 suggested that the core, virtually all of the mass of the comet, is a "dirty snowball" conglomeration of ice and dust.

Comet West Major proof of the theory of snowball effect rest on different data. On the one hand, the observed meteoric gases and particles are ejected to coma and tails of comets, the largest part of the gases are fragmentary molecules or radicals, the most common elements in space: hydrogen, carbon, nitrogen and oxygen. The radicals, for example, CH, NH, and OH May be broken away from the stable molecules CH4 (methane), NH3 (ammonia) and H2O (water), which is how ICES or complex, very cold compounds in the Core. Another fact to support the snowball theory is that the best-observed comet move in orbits that differ from Newton's gravitational constant movement. This provides clear evidence that the gases escape, a jet-action, the propulsion systems of the nucleus of a comet a little away from its otherwise predictable path. Besides the short-period comet, observed over many revolutions, tend to fade very slowly over time, than might be expected on the nature of the proposed structure of Whipple. Finally, the existence of the comet groups shows that the cometary nuclei are pretty solid.

The head of a comet, including the hazy coma, can the planet Jupiter in size. The fixed part of most comets, however, this represents only a few cubic kilometers. The dust-black core of the comet Halley, for example, is about 4 of 15 km (about 9 by 2.5 miles) in size with an estimated mass of 1017 grams

Comet KohoutekAs nucleus of the comet approaches the sun, dust the surface is hotter, more heat is through the crust, and the underground ice begins to sublimate. The resulting gas from the comet and carries with it some of the loosely bound dust particles. Sublimation begins when the comets are closer than about three astronomical units from the sun (an astronomical unit [AU] is about 150000000 km or miles 93000000). The chemical composition of gases is dominated by vaporising water (80 percent), followed by carbon monoxide, carbon dioxide, methane, ammonia, sulphur and carbon, quantitatively, in that order. Parents molecules from the cell nucleus fast break in subsidiaries molecules, radicals and ions. These absorb the sun's radiation and then reradiate it in a different wavelength. The dust and sunlight scattered. If within 1 AU from the Sun, a typical comet nucleus is surrounded by a spherical envelope, or coma, of gas and dust, which can take up to 100000 km (62000 km) across. The coma gases travel outwards with a speed of about 0.6 km per second, pull away dust particles from the nucleus.

On the eve of the sun, a comet can develop two tails. The solar wind of high-speed protons and electrons sweeps cometary ions in one direction, away from the sun, the production of a straight plasma. A second tail, consisting of dust particles on a micro-meters. The dust tail has a stronger curvature than the plasma tail and is usually shorter. He also points away from the sun because of the repulsive force exerted by solar radiation pressure on the minute particles. Larger particles from the nucleus, that the railways have almost the same parameters as the parent comet. Some profit from the Comets and others fall behind, until finally a ring of dust around the orbit of the comet. This is seen as a Meteoroid Stream.

Comet Hale BoppA meteor shower is in the earth's upper atmosphere when it passes through such a stream. As a comet back from the sun, the loss of gas and dust accompanying decline in the quantity, and the tails disappear. Some of the small comets with orbits have tails so short that they practically invisible. On the other hand, the tail of a comet has exceeded 320 million kilometers (200 million miles) long. The differences in the length of the tail, together with the degree of rapprochement with the sun and the earth, accounts for the differences in the visibility of the comet. From about 1400 comets on record, less than half of the tails were visible to the naked eye and less than 10 percent were striking.

Comets were once believed that the interstellar space. Although no detailed theory of origin is generally accepted, many astronomers now believe that comets from the outer, colder part of the solar system residual value of planetary material in the early days of the solar system. The Dutch astronomer Jan Hendrik Oort has proposed that a "storage cloud" of comet material has accumulated far beyond the orbit of Pluto, and that the gravitational effects of passing stars can send some of the material sunward, where they are visible, as comets.

Some accretion models of the solar system suggests that an early cometary bombardment of the planet may have an important role in the formation of the atmosphere and the oceans. In addition, comets May, the organic molecules necessary for the development of life on the planet. This theory remains unproved.

Comets are usually divided into short period comets (with periods of less than 200 years) and long-period comets (with periods of more than 200 years). Among the comet, you can easily with the naked eye, Comet Halley, with an average duration of 76 years is the only one that returns in a single life.

Comets have long been the superstitious as a sign of disaster or major events. The appearance of a comet has also led to the fear of the collision between the comet and the earth. The Earth, in fact, has passed through the tails of occasional comet without measurable effect. The collision of a comet nucleus with a large city would probably destroy the city but the probability of such an event is very small. Some scientists suggest, however, that collisions have taken place in the past and can even be astronomical for example, have a climatic role in the extinction of the dinosaurs.

Kometaren bodies were examined for the first time with spacecraft during the mid-1980s. In 1985 the U.S. probe known as the International cometary Explorer (ICE) by the Staubschweif of comet Giacobini-Zinner. The following year, spacecraft, which Japan and the Soviet Union, together with the above Giotto probe of the European Space Agency (ESA), flew by Comet Halley, transfer a lot of useful data on their composition and send photos from their core and coma .

In 1992 Comet Shoemaker-Levy 9 broke apart into 21 large fragments as reflected in the strong gravitational field of the planet Jupiter. During a week-long bombardment in July 1994, the fragments plunged into Jupiter's dense atmosphere at speeds of more than 210000 km / h (130000 mph). After the impact, the kinetic energy of the huge comet was converted into heat by massive explosions, so that some fireballs larger than the Earth.