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C O M E T S

 

History

           Comets were known at antiquity. More of them are more brillants & they appear so surprised in the sky, with a large trails that superstition saw them spell stars. This terror in the comets survived in the Middle Age at a little of Modern Age.

            Aristoteles & Ptolomeo knew that they are an irregular atmospherical effect. Seneca (4 a.C.-65d.C.), on the other hand, he spoke first time of them of autonomic celestial bodies. Regiomontano measured at 1472 the angular diameter of comets, & the first meditions of distances accomplished Tycho Brahe at 1577, with a conclusion that its comet was at 230 terrestial radium, only; & moved outside of our atmosphere. Therefore, it was abandoned last teories of terrestial origin of these phenomenons.

            But, it was necessary to pass some decades to change this opinion against the catholic church. Curiously, Galileo showed against this theory. Edmund Halley obtain to try at 1682 the comet that he saw it was the same one at 1607, 1531 & 1456, & he assigned eliptical orbit around the Sun with traslation period of 76 years. His precition of the comet that it will see again at 1758-9, but, he didn't live to see it. After, this comet was named Halley.

        The comets already were known in the Antiquity. Many of them are so shining and appear of so surprising way in skies, with their long tails, that the superstition saw in them maleficent stars. This terror to comets survived the Average Age and leaves from the Modern Era.

        Aristotle and Ptolomeo thought that they were irregularities of the terrestrial atmosphere. Séneca (4 a.C.-65d.C.), however, spoke for the first time of them like independent celestial bodies. Regiomontano measured in 1472 the angular diameter of comets, and the first measurements of distances made Tycho Brahe in 1577, reaching the conclusion that the comet observed by him had to be in favor of less to 230 terrestrial radios and moving, therefore, well outside the radius of attraction of the Earth. Therefore, before the evidence it had to leave the theories that defended the terrestrial origin of these phenomena.

        But still they had to spend several decades until this idea prevailed, the church, like no, influenced in it. Peculiarly Galileo was in opposition to her.   Edmund Halley was able to prove in 1682 that the comet that was observed that year was the same one of 1607, 1531 and 1456 and assigned to this object an extended elliptical orbit around the Sun, with a period of transfering of 76 years. Its prediction that the comet would return fulfilled, was year 1758-9 but it did not live to see it. Later, he received the comet name Halley in his honor.

 

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First appearance of the comet Halley

This drawing is the carpet of Bayeux of the century XI, that counts the history of the conquest of England by the normandos. This scene describes an appearance of the comet that later took its name from Edmund Halley.

Mary Evans Picture Library/Photo Researchers, Inc.

   

        Later after the invention of the eyeglass, they began to increase the numbers of discoveries. The oldest documents on comets date from millenium III a.C. The comet catalogue of Faldet , published in 1950, includes until year -2315 and registers until 1948 a total of 1738 objects. At the present time it is necessary to count on average of 20 comet discoveries per year.

        After telescope invention, they grow the numbers of comets. Documents formest about comets dated about III milenium b.C. The Faldest catalogue of comets, published at 1950, they have comets from -2315 to 1948 with a 1738 comets. Today, we have a new comets aproximality 20 per year.

 

Nomenclature

        A provisional denomination in agreement with the number of order of its discovery within every year is assigned to them of entrance. To the number of the year one adds a Latin letter to, b, c to him, etc.

        The comet receives in addition the last name to its discoverer, when it is discovered simultaneously and independently or more than a person, are used multiple names, so is the case of the Hale-Bopp comet.

        Later, once it is had definitive orbital elements, it is come to re-baptize it with the definitive form, that consist of already ordering them within every year by the date of their passage by the perihelion, for which Roman numbers are used, I, II, III, etc.

 

Composition

        A comet consists of a clear nucleus, of ice and rock, surrounded by a cloudy atmosphere called hair or comma. The American astronomer Fred L. Whipple described in 1949 the nucleus of the comets, that contains almost all the mass of the comet, as " dirty a snow ball " composed by a mixture of ice and dust.

        There are diverse data that sustain the theory of the snow ball. Of observed gases and meteoric particles that are expelled to form the hair and the tail of comets, most of gases is fragmentary or radical molecules of the elements most common in the space: hydrogen, carbon, nitrogen and oxygen. The radicals, for example CH, NH and OH, come from the breakage of some of stable molecules CH 4 (methane), NH 3 (ammoniac) and H 2 Or (water), that can remain in the nucleus like ice or like composed more complexes and very cold. Another fact that supports the theory of the snow ball is more that it has been verified, in observed comets, than their orbits are turned aside enough of the anticipated ones by the Newtonian laws. This demonstrates that the gas escape produces jet propulsion that slightly moves the nucleus of a comet outside its trajectory, on the other hand, easy to predict. In addition, the comets of short periods, observed throughout many revolutions, tend to vanish with time as it could be expected of those of the type of propose structure by Whipple. Finally, the existence of comet groups demonstrates that the cometarios nuclei are solid units.

 

           The head of a comet, including its diffuse hair, can be greater than the Jupiter planet. Nevertheless, the solid part of most of comets only has a volume of some cubical kilometers. For example, the nucleus darkened by the dust of the comet Halley has an approximated size of 15 by 4 kilometers.

halley.GIF (5982 bytes)

 

 

Periods and orbits

        The comets describe elliptical orbits, and the periods (the time that a comet in giving a return around the Sun takes) of about 200 have calculated I commit. The periods vary from 3.3 years for the comet Encke to 2,000 years for 1858 the Donati comet. The orbits of most of comets are so ample that they can seem parabolas (curved open that they would separate to comets from the Solar System), but as they suppose the astronomers from the technical analyses, they are ellipses of great eccentricity, possibly with periods of up to 40,000 years or mayores.

        Any comet is not known that has come near to the Earth with a hyperbolic orbit; this would mean that its origin was in the outer space of the Solar System. Nevertheless, some comets can never return to the Solar System due to the great alteration of their original orbits by the gravitational action of planets. This action has been observed in one more a smaller scale: about 60 I commit of short periods have orbits that have received the influence of the Jupiter planet, and it says that they belong to the Jupiter family. Their periods vary of 3.3 to 9 years.

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I commit: classification per period

           The comets are classified by their period, the time that take in completing an orbit around the Sun a comet of short period has an orbit nongreater than the one of Jupiter. A comet of long period follows a comparable route the orbit of Neptune; the comet Halley, with a period of about 76 years, is a comet example of long period. A comet of very long period can take thousands of years in turning around the Sun, or can happen through the Sun once and not return more.

 

Meteor comets and rains

            There are also one narrow relation between the orbits of comets and those of meteor rains . The Italian astronomer Giovanni Virginio Schiaparelli demonstrated that meteor shower Perseidas, that appears in August, moves in the same orbit that Comet III of 1862. Of the same form meteor shower Leonids, that appears in November, was in the same orbit that Comet I of 1866. It has been known of other rains different related to the orbits from comets and one assumes that are rest scattered by a comet throughout their orbit.

 

  Curves of light

            Next it is the comet relation in which I have made to date observations of its curves of light.   In all the related curves of light down, it is possible independently to obtain the curve of light of the table of values.

            Those that appears next they are in Word format (last version) computerized. If you wish that you it sends it, you send to me Correo / E-mail

 

Click Hyakutake (1996 B2)
Click Hale-Bopp (1995 O1)
Click Mc-Naught (2006 P1)

 Masm © (Last update 01.11.2007)