All about kites
Comets can be spectacular objects seen in the night sky. They were associated by the superstitious with disasters and other events important historical. Until the opposition from 1986 of Comet Halley, the actual nature of a comet nucleus has been the subject of debate among astronomers. The passage of the Giotto spacecraft near the nucleus of comet Halley and the many comments that have been undertaken around the world have greatly enhanced our understanding of nature of comets.
Because comets can be seen easily if the records of the observation of comets date back several centuries. It was a study of the observations history of several comets Halley, using the new theory of gravitation Newton showed that the orbits of several comets around the sun were almost identical. He postulates that all were the same object and predicts it would be reviewed sometime in the future. As we Soap, Halley comet will reappear in the calendar and has been in each of their travels in the direction of the sun.
target = "_blank" Kites>, as seen from Earth appear to have a kind of nucleus, which is surrounded by a brighter, more or less circular region called the "coma" from which one or more queues can be seen staggering Steering remote Sun These tails when the picture you can see different colors. Often there is a tail which is bluish filamentary structure and a series of amorphous tails are yellow. The comet's nucleus is expected that the center light coma. Coma and tail grow significantly as the comet approaches the sun to queue lengths, sometimes grows as much as 100 million miles.
The orbits of comets
The first calculation of orbits Halley's comet was made by, as mentioned above. Since then, the orbits of several hundreds of comets that were identified. Almost all are divided into two types, orbits periodicals, which are shaped very eccentric ellipses, and parabolic orbits.
The orbits Many comets have periods ranging from several hundred years to tens of millions of years, indicating that they spend much time far outside the orbit of Neptune and Pluto. The orbits of long-period comets are not confined to a plane as the orbits of the planets, these comets can appear anywhere in the sky. To explain the orbits of comets, astronomers have speculated the existence of two groups of comets at the edge of the solar system:
The Oort Cloud:
In 1950 the Dutch astronomer Jan Oort proposed that a large spherical cloud of comets surrounding the solar system. The Oort cloud is supposed to be about 1 light year radio, and can contain up to one billion small icy comets. Small perturbations in the slow movements of these bodies causes them to begin their long journey stop the inner solar system under the gravitational pull of the sun. The orbit of a body is a parabola with the sun as his home. As the comet approaches the sun, its speed increases to a maximum at its closest point is the result of which begins its journey home to the confines of the solar system, never seen again. The Oort cloud never has been observed, only theory, but its existence could explain the orbits of long period comets have orbital periods of more than 200 years.
At times during its journey through the solar system, a comet may pass near one of the major planets. If it's a close encounter, then the gravitational force the world will radically change the comet's orbit and may alter the parabolic orbit in a closed, elliptical orbit. The comet becomes a comet periodic with a period to return near the sun. Comet Halley is the best known example of such a comet. The existence of periodic comets, with periods orbitals of less than 200 years, has led to the proposal for a second source of comets:
The Kuiper Belt:
The Oort Cloud does not explain the existence of the comets that have orbital periods 200 years or less. In 1951, astronomer Gerald Kuiper suggested that another belt of comets existed beyond the orbit of Neptune, between 30 and 50 astronomical units (4.5 to 7.5 billion kilometers) from the sun. In 1988, a group of astronomers from the University Hawaii and the University of California at Berkeley, began the search for objects in the Kuiper belt, using a 2.2m telescope in Hawaii. They found that the first belt Kuiper in 1992. Further observations of Hawaii and the Hubble Space Telescope have discovered dozens of icy objects, each a few hundred kilometers in size and with periods orbital of a few hundred years. The Kuiper belt may be composed of Oort Cloud comets, which have been diverted in small orbits of Jupiter and other planets external.
Some comets have orbits very near future. For example, Comet Encke has a period of 3.5 years, the best known, putting its orbit within the orbit of Jupiter. It is generally believed that these inner solar system comets originate in the Oort Cloud and the Kuiper Belt, but spent enough about to be one of the giant planets deflected by its gravitational pull on a much smaller orbit.
The comet's nucleus
Until the probe Giotto showed us pictures of the nucleus of Halley's Comet was discussed in detail the nature of a comet nucleus. Now we know that the core is small, about 10-20 miles in diameter, is irregularly shaped (like a peanut), and is almost black. Therefore, the jets of gas and dust are forced by lightning the sun. We believe that under the black skin is a solid body composed of ices of all kinds, including water-ice, dry ice (carbon dioxide), ammonia, methane carbon and many other organic compounds across the ice mixed with dust. The dust contains silicates, carbon and carbon compounds.
Cometary coma
Around the nucleus is the bright coma. It is composed of gas and dust that was ejected from the sun evaporates the ice core. The parent molecules are distributed mainly in energy ultraviolet radiation from the Sun in simple compounds. These are not necessarily stable as the chemicals that we know on Earth, but that are simple combinations of atoms. For example, some of the most numerous are CN, C2, OH, C3 and NH2 + H2O. These pieces are broken most chemicals, such as water (H2O) and carbon compounds. The expelled gas and dust form a roughly spherical ball around the nucleus. This is much larger than the nucleus – coma of a bright comet may be millions of miles in diameter, while the core only 10 km more or less in width. Eat of the great comet of 1811 was larger than the sun.
The action of solar radiation and magnetic field associated with the solar wind remove the gas and dust of the coma and is "burned" away to form the comet's tail.
The tail of a comet
The gas is burned in the coma is ionized by solar radiation and is electrically charged. Is strongly affected by magnetic fields associated with the solar wind (a stream of particles charged particles ejected by the sun). The tail gas is made visible by the emission line gas excitation by radiation from the sun. This gives the gas tail characteristic blue color. The geometric shape of the tail is governed by the magnetic structures in the solar wind, but above all the gas tail points directly opposite committed to the direction of Dom
The dust is blown from the coma by radiation pressure from sunlight absorbed by the individual dust grains. It moves in a direction that is governed by the motion of the comet, the size of dust particles and the ejection velocity of the coma. The dust tail can be complex curve, multiple, even, but in general, will be the distance from the sun. Sometimes part due to projection effects, dust tail can be seen pointing the sun. It is only because the comet and the Earth are in motion and it was this part of the tail "Left Behind" in a place where it seems to point toward the sun. The dust tail is yellow, as it reflects sunlight to us.
The tail gas may be about 100 million kilometers long, while the dust tail is about 10 million km. The long tail observed in the folder is the great comet of 1843, he had a tail that was 250 million kilometers long (greater than the distance between Sun and Mars!).
The names of comets
A comet is named after its discoverer or discoverers. He also composed a series Series the year and a letter designation. Thus, all comets are a unique name. Comet Halley is one of the rare exceptions to the rule name. Halley discovered "his" comet, but has the honor of having his name associated with this for his pioneering work in determining the orbits of comets and demonstrating that this comet was periodic.
Comet Forecast
In addition to the periodic comets, whose orbital periods are well known and therefore, whose performance can be predicted with great accuracy, it is impossible to predict when comets can be seen in the sky. Most comets brightest and most spectacular were those that appeared only once and never seen again. When a comet is discovered, far from the Sun, it is difficult to predict how bright that will appear when it approaches the Earth and sun. Some comets appear to emit a large amount of gas and dust and cause long lines and other dramatic, while producing only a small amount of gas and dust, and almost no tail at all.
Name
Orbital period
Perihelion Date
Perihelion distance
Halley
76.1 years.
1986-02-09
UA 0587
Encke
3.30 years.
2003-12-28
UA 0340
Arrest
6.51 years.
2008-08-01
UA 1346
Tempel 1
5.51 years.
2005-07-07
UA 1500
Borrelly
6.86 years.
2001-09-14
UA 1358
Giacobini-Zinner
6.52 years.
1998-11-21
UA 0996
Grigg-Skjellerup
5.09 years.
1992-07-22
UA 0989
Crommelin
27.89 years.
1984-09-01
UA 0743
Honda-Pajdusakova Mrkos
5.29 years.
1995-12-25
UA 0528
Wirtanen
5.46 years.
2013-10-21
UA 1063
Tempel-Tuttle
32.92 years.
1998-02-28
UA 0982
Schwassmann-Wachmann 3
5.36 years.
2006-06-02
UA 0937
Kohoutek
6.24 years.
1973-12-28
UA 1571
West-Kohoutek-Ikemura
6.46 years.
2000-06-01
UA 1596
Wild 2
6.39 years.
2003-09-25
UA 1583
Chiron
50.7 years.
1996-02-14
UA 8460
Wilson-Harrington
4.29 years.
2001-03-26
UA 1000
Hale-Bopp
4000 years.
1997-03-31
UA 0914
Hyakutake
~ 40,000 years.
1996-05-01
UA 0230
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