Comets and asteroids
Us flies a terrible comet,
It sent the angered Creator.
We are powerless. Doomed planet.
Everyone died. Inevitable end.
In the obdurate depravity without measure
Meanwhile, talking to the peoples of the hypocrites:
We’ve had enough! Old our world.
And drink and eat and continue the feast.
Made in the epigraph of this section of row P. J. Beranger has written more than two hundred years ago, when astronomy was in the beginning of the knowledge of the laws of the Universe and every cosmic phenomenon was perceived as a supernatural manifestation of higher powers beyond the human mind. Over the past two hundred years of science, including astronomy, made a giant breakthrough in the understanding of the basic law of the structure and evolution of micro – and macro worlds, however, as before astronomers around the world are closely looking at the screen monitor in the hope of finding precursors “inevitable end”: large meteorites . comets and asteroids .
The problem of the study of comets can be divided into two parts, astrophysical and astrological. The first of them, in fact, is the subject of this section. The second is a tribute to the history, although like any branch of science, physics of comets would not have achieved such impressive results, not whether it is based on a descriptive “astrological” period. It is noteworthy that long before nachalnoi era of the ancient Babylonians and Egyptians knew how to predict eclipses of the Sun and understood that the number of comets in the Solar system is enormous. The Apollonia of the Medes and Pythagoras believed that the properties and structure of the comet, like the planets, and their frequency of occurrence in the sky is associated with the circulation around the Sun. But between these predictions and space travel to comet Halley could fit almost 26 centuries!
However, as in our day, science and charlatanism down to history side by side. And now, in the middle ages when the Royal names of Europe appear commentators comets, linking their appearance with various misfortunes caused by sky on reigning monarchs. So Charles V was convinced that the comet of 1556 is a harbinger of his death. This same comet, but already in 1664 made pretty worried Louis XIV. In 1856, according to descriptions of eyewitnesses, Europe was shaken by predictions about a collision with earth of a comet of Charles V. Fortunately, the collision did not happen, but the fear is still there – the fear of powerlessness before human civilization cosmic threat. And it should be noted that this fear is not unfounded.
Already in our century one of the most intriguing mysteries has been the phenomenon of the Tunguska meteorite . There is a strong argument in favor of the hypothesis that throughout the geological history of the Earth, she was repeatedly subjected to bombardment by large asteroids and even comets. Recently, in March 1989, a giant asteroid 1989FS diameter from 200 to 500 meters passed by Earth at a distance of only 700,000 kilometers, and its a thousand times more massive counterpart in the end of 1994 approached already at a distance of 100,000 km. But the most fantastic spectacle unfolded in the Solar system, July 16-22, 1994, when comet shoemaker-levy was torn apart and its pieces fell to the surface of Jupiter. Calculations show that if the path of this comet was not Jupiter, and the Earth, the consequences of such a collision would lead to destruction of our planet – the impact energy of fragments at the surface and perturbations of the atmosphere were in line to be the atomic bomb with a capacity of several million megatons of TNT! Recall that the power of the atomic bomb dropped on Hiroshima was only 25 thousand tons.
The above examples in no way exhaust the list of space objects that pose a potential danger for the Earth. In fact, it comprises about a thousand large asteroids and comets every year and updated with several new candidates.
Where “taken” by comets and asteroids in the Solar system? Easiest way to this question would be to get an answer in about 5-6 centuries BC, the philosophers of ancient China. Unlike Pythagoras, Eastern philosophy ocidental comets with the cosmic couriers, carrying on star provinces the will of the Emperor, governing the whole Universe.
How to write Sergey Kirsanov: “the News through the constellations of the Comet were taken: – On the mountain! Die a great star. ”
Unfortunately, modern science such elegant poetic response is unlikely to satisfy.
First of all, we are interested in the nature of these objects, the similarities and differences of their physical-chemical properties, history and evolution. These problems are, as twenty centuries ago, not only on the cutting edge of astronomy, but also attract permanent human interest. What is the difference between comets and asteroids . First of all, it should be emphasized that comets and asteroids have different physical and chemical composition . The basis of the comet’s nucleus is a conglomerate of ICES of methane, ammonia and water, covered with a relatively thin crust of rock. As it approaches the Sun there is an active evaporation of ice together with dust, thereby forming the atmosphere of the comet. This atmosphere, however, the properties and dynamics dramatically different from earth. The fact that the main factor determining the form of the atmosphere of the comet, is the pressure of solar radiation, which leads to the development of the “tail” of the comet.
For asteroids, the formation of the “tail” is completely absent. Cosmochemistry data show that the majority of asteroids are composed of carbonaceous chondrites, the efficiency of evaporation which under the influence of solar radiation is extremely small compared to the nuclei of comets. However, comets and asteroids have one common property. The age of comets and asteroids are virtually the same and is approaching the age of the Earth (4,5-4,6 billion. years). In addition, the timing of the appearance of comets is due to their rotation around the Sun. Therefore, along with the planets, asteroids and comets are part of the Solar system, its chemical composition and dynamics of rotation around the Sun “canning” information about the main stages of its formation!