Download presentation on comet microsoft powerpoint. Presentation on physics on the topic: Comets Physics teacher of the State Educational Institution “Sanatorium Boarding School of Kalininsk, Saratov Region” Marina Viktorovna Vasylyk

General information Presumably, long-period comets come to us from the Oort Cloud, which contains a huge number of cometary nuclei. Bodies located on the outskirts of the Solar system, as a rule, consist of volatile substances (water, methane and other ices) that evaporate when approaching the Sun.

To date, more than 400 short-period comets have been discovered. Many of them belong to so-called families. For example, approximately 50 of the shortest-period comets (their complete revolution around the Sun lasts 310 years) form the Jupiter family. Slightly smaller than the families of Saturn, Uranus and Neptune.

Comets arriving from deep space look like nebulous objects with a tail trailing behind them, sometimes reaching a length of several million kilometers. The comet's nucleus is a body of solid particles and ice shrouded in a hazy shell called a coma. A core with a diameter of several kilometers can have around it a coma 80 thousand km in diameter. Streams of sunlight knock gas particles out of the coma and throw them back, pulling them into a long smoky tail that moves behind her in space.

The brightness of comets depends very much on their distance from the Sun. Of all the comets, only a very small part comes close enough to the Sun and Earth to be seen with the naked eye. The most prominent ones are sometimes called "great comets."

The structure of comets Comets consist of a nucleus and a surrounding light, foggy shell (coma), consisting of gases and dust. As bright comets approach the Sun, they form a “tail” - a weak luminous stripe, which, as a result of light pressure and the action of the solar wind, is most often directed in the direction opposite to our star. The tails of celestial comets vary in length and shape. Some comets have them stretching across the entire sky. The tails of comets do not have sharp outlines and are almost transparent - stars are clearly visible through them. Its composition is varied: gas or tiny dust particles, or a mixture of both. The tails of comets are: straight and narrow, directed directly from the Sun; wide and slightly curved, deviating from the Sun; short, strongly inclined from the central luminary.

History of the discovery of comets For the first time, I. Newton calculated the orbit of a comet from observations of its movement against the background of stars and became convinced that, like the planets, it moved in the solar system under the influence of the Sun's gravity. Halley calculated and found that the comets observed in 1531, 1607 and 1682 were the same luminary, periodically returning to the Sun. At aphelion, the comet leaves the orbit of Neptune and after 75.5 years returns again to the Earth and the Sun. Halley first predicted the appearance of a comet in 1758. Many years after his death, it actually appeared. It was given the name Halley's Comet and was seen back in 1835 and in 1910 and in 1986.

Halley's Comet is a bright short-period comet that returns to the Sun every 7,576 years. It is the first comet for which an elliptical orbit was determined and the frequency of returns was established. Named in honor of E. Halley. Although many brighter long-period comets appear each century, Halley's Comet is the only short-period comet clearly visible to the naked eye. During its 1986 appearance, Halley's Comet became the first comet to be studied by spacecraft, including the Soviet Vega 1 and Vega 2 spacecraft, which provided data on the structure of the cometary nucleus and the mechanisms of formation of the comet's coma and tail.

The masses of comets are negligible, about a billion times less than the mass of the Earth, and the density of matter from their tails is practically zero. Therefore, “celestial guests” do not affect the planets of the solar system in any way. In May 1910, the Earth, for example, passed through the tail of Halley's Comet, but no changes occurred in the movement of our planet. On the other hand, the collision of a large comet with a planet can cause large-scale effects in the atmosphere and magnetosphere of the planet. A good and fairly well-studied example of such a collision was the collision of debris from comet Shoemaker-Levy 9 with Jupiter in July 1994. Comets and Earth

Presentation on the topic “Comets” Presentation on the topic “Comets” Completed by a student of class 11A of the Municipal Educational Institution Secondary School with UIOP No. 16 Khuzina Daria Head: physics teacher Dyachenko Larisa Borisovna In the past, comets were considered harbingers of misfortune. In the illustration (1579), the Aztec leader Montezuma observes the “heavenly sign” of the fall of his kingdom. Comet - (hairy star) is a small celestial body that has a nebulous appearance and orbits the sun along a conical section

Composition of the comet

• The core is a solid body or several bodies several kilometers long, which consists of a mixture of various ices and carbon dioxide, ammonia and dust
• Coma (appears when a comet approaches the Sun, the ice evaporates) consists of gases and dust
• Tail - (for bright comets when approaching the Sun) a weak luminous stripe directed in the direction opposite to the Sun

Hydrogen corona

Gas tail

Tail of dust

In total there are about 1000 data of celestial bodies.

Famous comets of the past

White dust and blue are clearly visible

plasma tails.

near the Milky Way

The most famous comets

Comet Halley's nucleus

Halley's Comet orbits in the direction opposite to the direction of rotation of the planets. Comet Shoemaker-Levy 9 came close to Jupiter in 1992 and was torn apart by its gravity.

In July 1994, fragments collided with Jupiter, causing fantastic effects in the planet's atmosphere.

Comet Hale–Bopp, 1997

Essay

in astronomy

"Comets"

student of 11 “A” class

Korneeva Maxima

Plan:

1. Introduction.

2. Historical facts, the beginning of the study of comets.

3. The nature of comets, their birth, life and death.

4. Structure and composition of a comet.

5.

6. Conclusion.

7. List of references.

1. Introduction.

Comets are among the most spectacular bodies in the solar system. These are peculiar space icebergs, consisting of frozen gases of complex chemical composition, water ice and refractory mineral matter in the form of dust and larger fragments. Every year 5-7 new comets are discovered and quite often once every 2-3 years a bright comet with a large tail passes near the Earth and the Sun. Comets are of interest not only to astronomers, but also to many other scientists: physicists, chemists, biologists, historians... Quite complex and expensive research is constantly being carried out. What caused such keen interest in this phenomenon? It can be explained by the fact that comets are a capacious and still far from fully explored source of information useful to science. For example, comets “told” scientists about the existence of the solar wind, there is a hypothesis that comets are the cause of the emergence of life on earth, they can provide valuable information about the emergence of galaxies... But it should be noted that the student does not receive a very large amount of knowledge in this area due to time constraints. Therefore, I would like to expand my knowledge and also learn more interesting facts on this topic.

2. Historical facts, the beginning of the study of comets.

When did people first think about bright tailed “stars” in the night sky? The first written mention of the appearance of a comet dates back to 2296 BC. The movement of the comet through the constellations was carefully observed by Chinese astronomers. The ancient Chinese saw the sky as a vast country, where the bright planets were the rulers and the stars were the authorities. Therefore, ancient astronomers considered a constantly moving comet to be a messenger, a courier delivering dispatches. It was believed that any event in the starry sky was preceded by a decree of the heavenly emperor, delivered by a comet-messenger.

Ancient people were terribly afraid of comets, prescribing for them many earthly cataclysms and misfortunes: pestilence, famine, natural disasters... They were afraid of comets because they could not find a sufficiently clear and logical explanation for this phenomenon. This is where numerous myths about comets arise. The ancient Greeks imagined a head with flowing hair as any comet that was bright enough and visible to the naked eye. This is where the name came from: the word “comet” comes from the ancient Greek “cometis”, which means “hairy”.

Aristotle was the first to try to scientifically substantiate the phenomenon. Not noticing any regularity in the appearance and movement of comets, he proposed to consider them as flammable atmospheric vapors. Aristotle's opinion became generally accepted. However, the Roman scientist Seneca tried to refute the teachings of Aristotle. He wrote that “a comet has its own place between celestial bodies..., it describes its path and does not go out, but only moves away.” But his insightful assumptions were considered reckless, since Aristotle’s authority was too high.

But due to uncertainty, lack of consensus and explanation for the phenomenon of “tailed stars,” people continued to consider them something supernatural for a long time. In comets they saw fiery swords, bloody crosses, burning daggers, dragons, severed heads... The impressions from the appearance of bright comets were so strong that even enlightened people and scientists succumbed to prejudices: for example, the famous mathematician Bernoulli said that the tail of a comet is a sign of anger God's

During the Middle Ages, scientific interest in the phenomenon reappeared. One of the outstanding astronomers of that era, Regiomontanus, treated comets as objects of scientific research. Regularly observing all the appearing luminaries, he was the first to describe the trajectory of movement and direction of the tail. In the 16th century, the astronomer Apian, conducting similar observations, came to the conclusion that the tail of a comet is always directed in the direction opposite to the Sun. A little later, the Danish astronomer Tycho Brahe began to observe the movement of comets with the highest accuracy for that time. As a result of his research, he proved that comets are celestial bodies more distant than the Moon, and thereby refuted Aristotle's teaching on atmospheric evaporation.

But, despite the research, getting rid of prejudices was very slow: for example, Louis XIV was very afraid of the comet of 1680, as he considered it a harbinger of his death.

The greatest contribution to the study of the true nature of comets was made by Edmond Halley. His main discovery was to establish the periodicity of the appearance of the same comet: in 1531, in 1607, in 1682. Fascinated by astronomical research, Halley became interested in the movement of the comet of 1682 and began calculating its orbit. He was interested in the path of its movement, and since Newton had already carried out similar calculations, Halley turned to him. The scientist immediately gave the answer: the comet will move in an elliptical orbit. At Halley's request, Newton outlined his calculations and theorems in the treatise “De Motu”, that is, “On Motion”. Having received Newton's help, he began calculating cometary orbits from astronomical observations. He managed to collect information about 24 comets. Thus, the first catalog of cometary orbits appeared. In his catalog, Halley found that the three comets were very similar in their characteristics, from which he concluded that these were not three different comets, but rather periodic appearances of the same comet. The period of its appearance turned out to be 75.5 years. It was subsequently named Halley's Comet.

After Halley's catalog, several more catalogs appeared, which list all comets that appeared both in the distant past and at the present time. The most famous of them are: the catalog of Balde and Obaldia, as well as, first published in 1972, the catalog of B. Marsden, which is considered the most accurate and reliable.

3. The nature of comets, their birth, life and death.

Where do “tailed stars” come to us from? There are still lively discussions about the sources of comets, but a unified solution has not yet been developed.

Back in the 18th century, Herschel, observing nebulae, suggested that comets were small nebulae moving in interstellar space. In 1796, Laplace, in his book “Exposition of the World System,” expressed the first scientific hypothesis about the origin of comets. Laplace considered them to be fragments of interstellar nebulae, which is incorrect due to the differences in the chemical composition of both. However, his assumption that these objects were of interstellar origin was confirmed by the presence of comets with almost parabolic orbits. Laplace also considered short-period comets to come from interstellar space, but once captured by the gravity of Jupiter and transferred by it to short-period orbits. Laplace's theory still has supporters today.

In the 50s, the Dutch astronomer J. Oort proposed a hypothesis about the existence of a comet cloud at a distance of 150,000 AU. e. from the Sun, formed as a result of the explosion of the 10th planet of the Solar system - Phaethon, which once existed between the orbits of Mars and Jupiter. According to Academician V.G. Fesenkov, the explosion occurred as a result of too close a rapprochement between Phaeton and Jupiter, since with such a rapprochement, due to the action of colossal tidal forces, strong internal overheating of Phaeton arose. The force of the explosion was enormous. To prove the theory, one can cite the calculations of Van Flandern, who studied the distribution of elements of 60 long-period comets and came to the conclusion that 5 million years ago, a planet with a mass of 90 Earth masses (comparable in mass to Saturn) exploded between the orbits of Jupiter and Mars. As a result of such an explosion, most of the matter in the form of comet nuclei (fragments of the icy crust), asteroids and meteorites left the solar system, part of it lingered on its periphery in the form of the Oort cloud, part of the matter remained in the former orbit of Phaethon, where it now circulates in in the form of asteroids, comet nuclei and meteorites.

Fig.: Paths of long-period comets to the outskirts of the Solar system (Phaethon explosion?)

Some cometary nuclei have retained relict ice under a loose heat-insulating layer of refractory components, and short-period comets moving in almost circular orbits are still sometimes discovered in the asteroid belt. An example of such a comet is comet Smirnova-Chernykh, discovered in 1975.

Currently, the hypothesis of gravitational condensation of all bodies of the Solar System from a primary gas-dust cloud, which had a chemical composition similar to that of the Sun, is generally accepted. In the cold zone of the cloud, the giant planets condensed: Jupiter, Saturn, Uranus, Neptune. They absorbed the most abundant elements of the protoplanetary cloud, as a result of which their masses increased so much that they began to capture not only solid particles, but also gases. In the same cold zone, icy nuclei of comets also formed, which partly went into the formation of giant planets, and partly, as the masses of these planets grew, they began to be thrown to the periphery of the Solar system, where they formed a “reservoir” of comets - the Oort cloud.

As a result of studying the elements of almost parabolic cometary orbits, as well as the application of celestial mechanics methods, it was proven that the Oort cloud actually exists and is quite stable: its half-life is about one billion years. At the same time, the cloud is constantly replenished from different sources, so it does not cease to exist.

F. Whipple believes that in the Solar System, in addition to the Oort cloud, there is also a closer region densely populated with comets. It is located beyond the orbit of Neptune, contains about 10 comets, and it is it that causes those noticeable disturbances in the movement of Neptune, which were previously attributed to Pluto, since it has a mass two orders of magnitude greater than the mass of Pluto. This belt could have formed as a result of the so-called “diffusion of cometary orbits,” the theory of which was most fully developed by the Riga astronomer K. Steins. It consists of a very slow accumulation of small planetary disturbances, which results in a gradual reduction of the semi-major axis of the comet's elliptical orbit.

Scheme of diffusion of cometary orbits:

Thus, over millions of years, many comets that previously belonged to the Oort cloud change their orbits so that their perihelia (the closest distance from the Sun) begin to concentrate near the most distant giant planet Neptune, which has a large mass and an extended sphere of action. Therefore, the existence of the comet belt predicted by Whipple beyond Neptune is quite possible.

Subsequently, the evolution of the cometary orbit from the Whipple belt proceeds much more rapidly, depending on the approach to Neptune. When approaching, a strong transformation of the orbit occurs: Neptune acts with its magnetic field in such a way that after leaving its sphere of influence, the comet begins to move in a sharply hyperbolic orbit, which leads either to its ejection from the solar system, or it continues to move into the planetary system, where it can again be exposed to the influence of the giant planets, or will move towards the Sun in a stable elliptical orbit, with its aphelion (the point of greatest distance from the Sun) indicating that it belongs to the Neptune family.

According to E.I. Kazimirchak-Polonskaya, diffusion leads to the accumulation of circular cometary orbits also between Uranus and Neptune, Saturn and Uranus, Jupiter and Saturn, which are also sources of cometary nuclei.

A number of difficulties encountered in the capture hypothesis, especially in Laplace's time, in explaining the origin of comets, prompted scientists to look for other sources of comets. For example, the French scientist Lagrange, based on the absence of sharp initial hyperbolas and the presence of only direct movements in the system of short-period comets in the Jupiter family, put forward a hypothesis about the eruptive, that is, volcanic, origin of comets from various planets. Lagrange was supported by Proctor, who explained the existence of comets in the solar system by strong volcanic activity on Jupiter. But in order for a fragment of Jupiter’s surface to overcome the planet’s gravitational field, it would need to be given an initial speed of about 60 km/s. The appearance of such velocities during volcanic eruptions is unrealistic, therefore the hypothesis of the eruptive origin of comets is considered physically untenable. But in our time it is supported by a number of scientists, developing additions and clarifications to it.

There are also other hypotheses about the origin of comets, which are not as widespread as the hypotheses about the interstellar origin of comets, the Oort cloud and the eruptive formation of comets.

4. Structure and composition of the comet.

The small nucleus of the comet is its only solid part; almost all of its mass is concentrated in it. Therefore, the nucleus is the root cause of the rest of the complex of cometary phenomena. Comet nuclei are still inaccessible to telescopic observations, since they are veiled by the luminous matter surrounding them, continuously flowing from the nuclei. Using high magnifications, you can look into the deeper layers of the luminous gas-dust shell, but what remains will still be significantly larger in size than the true dimensions of the core. The central condensation visible in the comet's atmosphere visually and in photographs is called the photometric nucleus. It is believed that the comet’s nucleus itself is located in its center, that is, the center of mass is located. However, as the Soviet astronomer D. O. Mokhnach showed, the center of mass may not coincide with the brightest region of the photometric core. This phenomenon is called the Mokhnach effect.

The hazy atmosphere surrounding the photometric core is called coma. The coma, together with the nucleus, makes up the head of the comet - a gas shell that is formed as a result of the heating of the nucleus as it approaches the Sun. Far from the Sun, the head looks symmetrical, but as it approaches it, it gradually becomes oval, then lengthens even more, and on the side opposite from the Sun, a tail develops from it, consisting of gas and dust that make up the head.

The nucleus is the most important part of a comet. However, there is still no consensus on what it actually is. Even in the time of Laplace, there was an opinion that the comet's nucleus was a solid body consisting of easily evaporating substances such as ice or snow, which quickly turned into gas under the influence of solar heat. This classic icy model of the cometary nucleus has been significantly expanded in recent times. The most widely accepted model is the core model developed by Whipple - a conglomerate of refractory rocky particles and frozen volatile components (methane, carbon dioxide, water, etc.). In such a core, ice layers of frozen gases alternate with dust layers. As the gases heat up, they evaporate and carry clouds of dust with them. This explains the formation of gas and dust tails in comets, as well as the ability of small nuclei to release gases.

According to Whipple, the mechanism for the outflow of matter from the nucleus is explained as follows. In comets that have made a small number of passages through perihelion - the so-called “young” comets - the surface protective crust has not yet had time to form, and the surface of the nucleus is covered with ice, so gas evolution proceeds intensively through direct evaporation. The spectrum of such a comet is dominated by reflected sunlight, which makes it possible to spectrally distinguish “old” comets from “young” ones. Comets with large orbital semi-axes are usually called “young”, since it is assumed that they are penetrating the inner regions of the Solar System for the first time. “Old” comets are comets with a short period of revolution around the Sun, which have passed their perihelion many times. In “old” comets, a refractory screen is formed on the surface, since during repeated returns to the Sun, the surface ice melts and becomes “contaminated.” This screen protects the ice underneath well from exposure to sunlight.

Whipple's model explains many cometary phenomena: abundant gas emission from small nuclei, the cause of non-gravitational forces that deflect the comet from the calculated path. The flows emanating from the core create reactive forces, which lead to secular accelerations or decelerations in the movement of short-period comets.

There are also other models that deny the presence of a monolithic core: one represents the core as a swarm of snowflakes, another as a cluster of rock and ice blocks, the third says that the core periodically condenses from particles of a meteor swarm under the influence of planetary gravity. Still, the Whipple model is considered the most plausible.

The masses of comet nuclei are currently determined extremely uncertainly, so we can talk about a probable range of masses: from several tons (microcomets) to several hundred, and possibly thousands of billions of tons (from 10 to 10-10 tons).

The comet's coma surrounds the nucleus in a hazy atmosphere. In most comets, the coma consists of three main parts, which differ markedly in their physical parameters:

1) the closest area adjacent to the nucleus - internal, molecular, chemical and photochemical coma,

2) visible coma, or radical coma,

3) ultraviolet, or atomic coma.

At a distance of 1 a. That is, from the Sun the average diameter of the internal coma is D = 10 km, visible D = 10-10 km and ultraviolet D = 10 km.

In the internal coma, the most intense physical and chemical processes occur: chemical reactions, dissociation and ionization of neutral molecules. In a visible coma, consisting mainly of radicals (chemically active molecules) (CN, OH, NH, etc.), the process of dissociation and excitation of these molecules under the influence of solar radiation continues, but less intensely than in an internal coma.

Fig.: Photo of Comet Hyakutake in the ultraviolet range.

L.M. Shulman, based on the dynamic properties of matter, proposed dividing the cometary atmosphere into the following zones:

1) wall layer (area of ​​evaporation and condensation of particles on the ice surface),

2) perinuclear region (region of gas-dynamic movement of matter),

3) transition region,

4) the region of free molecular expansion of cometary particles into interplanetary space.

But not every comet must have all the listed atmospheric regions.

As the comet approaches the Sun, the diameter of the visible head increases day by day; after passing the perihelion of its orbit, the head increases again and reaches its maximum size between the orbits of Earth and Mars. In general, for the entire set of comets, the diameters of the heads are within wide limits: from 6000 km to 1 million km.

The heads of comets take on a variety of shapes as the comet moves around its orbit. Far from the Sun they are round, but as they approach the Sun, under the influence of solar pressure, the head takes the form of a parabola or a chain line.

S. V. Orlov proposed the following classification of comet heads, taking into account their shape and internal structure:

1. Type E; - observed in comets with bright comas framed on the Sun's side by luminous parabolic shells, the focus of which lies in the comet's nucleus.

2. Type C; - observed in comets whose heads are four times weaker than type E heads and resemble an onion in appearance.

3. Type N; - observed in comets that lack both coma and shells.

4. Q type; - observed in comets that have a weak protrusion towards the Sun, that is, an anomalous tail.

5. Type h; - observed in comets, in the head of which uniformly expanding rings are generated - halos with a center in the nucleus.

The most impressive part of a comet is its tail. The tails are almost always directed in the direction opposite to the Sun. Tails consist of dust, gas and ionized particles. Therefore, depending on the composition, the tail particles are repelled in the direction opposite to the Sun by forces emanating from the Sun.

F. Bessel, studying the shape of the tail of Halley's comet, first explained it by the action of repulsive forces emanating from the Sun. Subsequently, F.A. Bredikhin developed a more advanced mechanical theory of cometary tails and proposed dividing them into three separate groups, depending on the magnitude of the repulsive acceleration.

Analysis of the spectrum of the head and tail showed the presence of the following atoms, molecules and dust particles:

1. Organic C, C, CCH, CN, CO, CS, HCN, CHCN.

2. Inorganic H, NH, NH, O, OH, HO.

3. Metals - Na, Ca, Cr, Co, Mn, Fe, Ni, Cu, V, Si.

4. Ions - CO, CO, CH, CN, N, OH, HO.

5. Dust - silicates (in the infrared region).

The mechanism of luminescence of cometary molecules was deciphered in 1911 by K. Schwarzschild and E. Kron, who came to the conclusion that this is a mechanism of fluorescence, that is, re-emission of sunlight.

Sometimes quite unusual structures are observed in comets: rays emerging from the nucleus at different angles and collectively forming a radiant tail; halos - systems of expanding concentric rings; contracting shells - the appearance of several shells constantly moving towards the core; cloud formations; omega-shaped tail bends that appear during solar wind inhomogeneities.

Fig.: Comet with a radiant tail.

There are also non-stationary processes in the heads of comets: flashes of brightness associated with increased short-wave radiation and corpuscular flows; separation of nuclei into secondary fragments.

5. Modern comet research.

Project "Vega".

Project Vega (Venus - Halley's Comet) was one of the most complex in the history of space exploration. It consisted of three parts: studying the atmosphere and surface of Venus using landers, studying the dynamics of the atmosphere of Venus using balloon probes, flying through the coma and plasma shell of Comet Halley.

The automatic station “Vega-1” launched from the Baikonur Cosmodrome on December 15, 1984, followed by “Vega-2” 6 days later. In June 1985, they passed near Venus one after another, successfully conducting research related to this part of the project.

But the most interesting was the third part of the project - the study of Halley's Comet. For the first time, spacecraft had to “see” the comet’s nucleus, which was elusive to ground-based telescopes. The meeting of Vega 1 with the comet occurred on March 6, and Vega 2 on March 9, 1986. They passed at a distance of 8900 and 8000 kilometers from its core.

The most important task in the project was to study the physical characteristics of the comet's nucleus. For the first time, the core was considered as a spatially resolved object, its structure, dimensions, infrared temperature were determined, and estimates of its composition and characteristics of the surface layer were obtained.

At that time, it was not yet technically possible to land on the comet's nucleus, since the speed of the encounter was too high - in the case of Halley's comet it was 78 km/s. It was dangerous even to fly too close, as comet dust could destroy the spacecraft. The flight distance was chosen taking into account the quantitative characteristics of the comet. Two approaches were used: remote measurements using optical instruments and direct measurements of matter (gas and dust) leaving the core and crossing the trajectory of the apparatus.

The optical instruments were placed on a special platform, developed and manufactured jointly with Czechoslovak specialists, which rotated during the flight and tracked the trajectory of the comet. With its help, three scientific experiments were carried out: television filming of the nucleus, measurement of the flux of infrared radiation from the nucleus (thereby determining the temperature of its surface) and the spectrum of infrared radiation of the internal “perinuclear” parts of the coma at wavelengths from 2.5 to 12 micrometers in order to determine it composition. IR radiation studies were carried out using an IR infrared spectrometer.

The results of optical research can be formulated as follows: the core is an elongated monolithic body of irregular shape, the dimensions of the major axis are 14 kilometers, and the diameter is about 7 kilometers. Every day, several million tons of water vapor leave it. Calculations show that such evaporation can come from an icy body. But at the same time, the instruments established that the surface of the core is black (reflectivity less than 5%) and hot (about 100 thousand degrees Celsius).

Measurements of the chemical composition of dust, gas and plasma along the flight path showed the presence of water vapor, atomic (hydrogen, oxygen, carbon) and molecular (carbon monoxide, carbon dioxide, hydroxyl, cyanogen, etc.) components, as well as metals with an admixture of silicates.

The project was implemented with broad international cooperation and with the participation of scientific organizations from many countries. As a result of the Vega expedition, scientists saw the cometary nucleus for the first time and obtained a large amount of data on its composition and physical characteristics. The rough diagram was replaced by a picture of a real natural object that had never been observed before.

NASA is currently preparing three large expeditions. The first of them is called “Stardust”. It involves the launch in 1999 of a spacecraft that will pass 150 kilometers from the nucleus of comet Wild 2 in January 2004. Its main task: to collect comet dust for further research using a unique substance called “aerogel”. The second project is called “Contour” (“COmet Nucleus TOUR”). The device will be launched in July 2002. It will encounter Comet Encke in November 2003, Comet Schwassmann-Wachmann 3 in January 2006, and finally Comet d'Arrest in August 2008. It will be equipped with advanced technical equipment that will make it possible to obtain high-quality photographs of the nucleus in various spectra, as well as collect cometary gas and dust. The project is also interesting because the spacecraft, using the Earth's gravitational field, can be reoriented in 2004-2008 to a new comet. The third project is the most interesting and complex. It is called “Deep Space 4” and is part of a research program called “NASA New Millennium Program”. It is expected to land on the nucleus of comet Tempel 1 in December 2005 and return to Earth in 2010. The spacecraft will explore the comet's nucleus, collect and deliver soil samples to Earth.

Figure: Project Deep Space 4.

The most interesting events over the past few years become: the appearance of Comet Hale-Bopp and the fall of Comet Schumacher-Levy 9 on Jupiter.

Comet Hale-Bopp appeared in the sky in the spring of 1997. Its period is 5900 years. There are some interesting facts associated with this comet. In the fall of 1996, American amateur astronomer Chuck Shramek transmitted to the Internet a photograph of a comet, in which a bright white object of unknown origin, slightly flattened horizontally, was clearly visible. Shramek called it a “Saturn-like object” (or “SLO” for short). The size of the object was several times greater than the size of the Earth.

Rice.: SLO is a mysterious satellite of the comet.

The reaction of official scientific representatives was strange. Sramek's image was declared a fake and the astronomer himself a hoaxer, but no clear explanation of the nature of SLO was offered. The picture published on the Internet caused an explosion of occultism, a huge number of stories were spread about the coming end of the world, the “dead planet of an ancient civilization,” evil aliens preparing to take over the Earth with the help of a comet, even the expression: “What the hell is going on?” (“What the hell is going on?”) was paraphrased in “What the Hale is going on?”... It is still not clear what kind of object it was, what its nature was.

Fig.: Mystical “eyes” of a comet.

Preliminary analysis showed that the second “core” was a star in the background, but subsequent images refuted this assumption. Over time, the “eyes” connected again, and the comet took on its original appearance. This phenomenon has also not been explained by any scientist.

Thus, comet Hale-Bopp was not a standard phenomenon; it gave scientists a new reason to think.

Figure: Comet Hale-Bopp in the night sky.

Another sensational event was the fall of the short-period comet Schumacher-Levy 9 onto Jupiter in July 1994. The comet's nucleus in July 1992, as a result of its approach to Jupiter, split into fragments, which subsequently collided with the giant planet. Due to the fact that the collisions occurred on the night side of Jupiter, terrestrial researchers could only observe flashes reflected by the planet’s satellites. The analysis showed that the diameter of the fragments is from one to several kilometers. 20 comet fragments fell on Jupiter.

Fig.: Comet Schumacher-Levy 9 falling on Jupiter.

Fig.: Photograph of Jupiter in the IR range after the fall of the comet.

Scientists say that the breakup of a comet into pieces is a rare event, the capture of a comet by Jupiter is an even rarer event, and the collision of a large comet with a planet is an extraordinary cosmic event.

Recently, in an American laboratory, on one of the most powerful Intel Teraflop computers with a performance of 1 trillion operations per second, a model of the fall of a comet with a radius of 1 kilometer to the Earth was calculated. The calculations took 48 hours. They showed that such a cataclysm would be fatal for humanity: hundreds of tons of dust would rise into the air, blocking access to sunlight and heat, when it fell into the ocean, a giant tsunami would be formed, destructive earthquakes would occur... According to one hypothesis, dinosaurs became extinct as a result of the fall of a great comet or asteroid. In Arizona, there is a crater with a diameter of 1219 meters, formed after the fall of a meteorite 60 meters in diameter. The explosion was equivalent to the explosion of 15 million tons of trinitrotoluene. It is assumed that the famous Tunguska meteorite of 1908 had a diameter of about 100 meters. Therefore, scientists are now working to create a system for early detection, destruction or deflection of large cosmic bodies flying close to our planet.

6. Conclusion.

Thus, it turned out that, despite their careful study, comets still conceal many mysteries. Some of these beautiful “tailed stars”, shining from time to time in the evening sky, can pose a real danger to our planet. But progress in this area does not stand still, and, most likely, our generation will already witness a landing on a cometary nucleus. Comets are not yet of practical interest, but studying them will help to understand the fundamentals and causes of other events. The comet is a space wanderer, it passes through very remote areas inaccessible to research, and perhaps it “knows” what is happening in interstellar space.

7. Sources of information:

· K.I. Churyumov “Comets and their observation” (1980)

· Internet: NASA server (www.nasa.gov), Chuck Shramek's page and other resources.

· B. A. Vorontsov-Velyamov “Laplace” (1985)

· “Soviet Encyclopedic Dictionary” (1985)

· B. A. Vorontsov-Velyamov “Astronomy: textbook for grade 10” (1987)

Description of the presentation by individual slides:

1 slide

Slide description:

The presentation was prepared by G.F. Poleshchuk State Educational Institution JSC "Comprehensive School at Penitentiary Institutions" COMET

2 slide

Slide description:

What a luxurious wonder! Almost occupying half the world, Mysterious, very beautiful, A comet hovers over the Earth. And I want to think: - Where did the bright miracle come to us from? And I want to cry when It flies away without a trace. And they tell us: - This is ice! And her tail is dust and water! It doesn’t matter, a Miracle is coming to us, And a Miracle is always beautiful! Rimma Aldonina Ancient people were afraid of a comet. They called it the tailed star for this. Great sins were attributed to her: Diseases and wars - a whole bunch of nonsense!

3 slide

Slide description:

Any guesses about where comets come from? According to the first, comets are born and come to us from some region located outside the solar system. According to the second assumption, comets are born in a hypothetical Oort cloud, located somewhere at the very borders of the Solar system, perhaps beyond the orbits of Uranus or Pluto. Halley first predicted the appearance of a comet in 1758. Many years after his death, she actually appeared. It was given the name Halley's Comet and was seen back in 1835, 1910 and 1986.

4 slide

Slide description:

Comet (translated from ancient Greek - hairy, shaggy) is a small celestial body revolving around the Sun with a very extended orbit. As the comet approaches the Sun, it forms a coma and sometimes a tail of gas and dust.

5 slide

Slide description:

6 slide

Slide description:

Comet nuclei are similar in size to small asteroids. The diameter of the comet's head sometimes reaches hundreds of thousands of kilometers, and its tails extend for tens and hundreds of millions of kilometers. Coma is a hazy atmosphere that surrounds the photometric core and gradually fades away, merging with the background of the sky.

7 slide

Slide description:

The main part of the comet's matter is concentrated in the nucleus, which apparently consists of a mixture of frozen gases (ammonia, methane, carbon dioxide, nitrogen, cyanide, etc.) and dust particles, metal and stone particles of different sizes. The comet's tail consists of very rarefied matter, through which stars shine through. The upper limit of the mass of comets is 10-4 Earth masses.

8 slide

Slide description:

Comets shine with reflected and scattered sunlight. The cold glow of gas (fluorescence) occurs under the influence of solar radiation. The closer a comet comes to the Sun, the more its core warms up, the release of gases and dust increases, but at the same time the light pressure on it increases. Therefore, the comet's tail grows and becomes more and more noticeable. In addition to the pressure of light, the tails of comets are affected by streams of charged particles emitted by the Sun (solar wind).

Slide 9

Slide description:

The orbits of most comets are highly elongated ellipses. At perihelion, comets come close to the Sun (and to the Earth), and at aphelion they move away from it by hundreds of thousands of astronomical units, going far beyond the orbit of Pluto. Comets whose orbital eccentricities are not very large have short periods of revolution around the Sun.

10 slide

Slide description:

Classification of comets: I. Short-period – comets with an orbital period of less than 200 years. Halley's Comet is the most famous of the short-period comets. In 1704, the English astronomer E. Halley proved that the comets of 1531, 1607 and 1682 are the same, revolving around the Sun in an elongated orbit with a period of 76 years. It was named Halley's Comet in his honor. This is one of the brightest comets. The last time she visited us was in 1986. (Photo from Earth of Comet Halley 1986) Comet Encke is the shortest period of revolution around the Sun - 3.3 years. It has been observed for a century and a half.

11 slide

Slide description:

II. Long-period comets with orbital periods of more than 200 years. Currently, about 700 of them have been discovered. About a sixth of all known long-period comets are “new,” i.e. they were observed only during one approach to the Sun. Obviously, their orbit is not closed (parabolic), so they are called parabolic. The long-period comet Hale-Bopp was discovered in the vicinity of the Sun in July 1995. The name consists of the names of the scientists who discovered it. Comet Hyakutake C/1996 B2 is a long-period comet discovered on January 30, 1996 by Japanese amateur astronomer Yuji Hyakutake.

12 slide

Slide description:

Can the Earth meet a comet? Like any planet, the Earth is not immune from encounters with a comet. And such a meeting took place in May 1910: the Earth passed through the tail of Comet Halley. At the same time, no serious changes occurred in the life of the Earth, although the most incredible assumptions were made. The newspapers were full of headlines like: “Will the Earth perish this year?” Experts gloomily predicted that the shining gas plume contained poisonous cyanide gases, meteorite bombardments and other exotic phenomena in the atmosphere were expected. The fears turned out to be empty. No harmful auroras, no violent meteor showers, or any other unusual phenomena were noted. Even in air samples taken from the upper layers of the atmosphere, not the slightest change was detected.