Since ancient times, people have sought to uncover the secrets that the sky is fraught with. Since the first telescope was created, scientists have been gradually collecting grains of knowledge that are hidden in the boundless expanses of space. It's time to find out where the messengers from space came from - comets and meteorites.

What is a comet?

If we examine the meaning of the word "comet", then we come to its ancient Greek equivalent. It literally means "with long hair". Thus, the name was given in view of the structure of this Comet has a "head" and a long "tail" - a kind of "hair". The head of a comet consists of a nucleus and perinuclear substances. The loose core may contain water, as well as gases such as methane, ammonia, and carbon dioxide. The Churyumov-Gerasimenko comet, discovered on October 23, 1969, has the same structure.

How the comet was previously represented

In ancient times, our ancestors were in awe of her and invented various superstitions. Even now there are those who associate the appearance of comets with something ghostly and mysterious. Such people may think that they are wanderers from another world of souls. Where did this one come from? Perhaps the whole point is that the appearance of these heavenly creatures has ever coincided with some kind of unkind incident.

However, time passed, and the idea of ​​\u200b\u200bwhat small and large comets were changed. For example, such a scientist as Aristotle, investigating their nature, decided that it was a luminous gas. After a while, another philosopher named Seneca, who lived in Rome, suggested that comets are bodies in the sky moving in their orbits. However, it was only after the creation of the telescope that real progress in their study was made. When Newton discovered the law of gravity, things went up.

Current ideas about comets

Today, scientists have already established that comets consist of a solid core (from 1 to 20 km in thickness). What is the nucleus of a comet made of? From a mixture of frozen water and space dust. In 1986, pictures of one of the comets were taken. It became clear that its fiery tail is an ejection of a stream of gas and dust that we can observe from the earth's surface. What is the reason for this "fiery" release? If an asteroid flies very close to the Sun, then its surface heats up, which leads to the release of dust and gas. Solar energy puts pressure on the solid material that makes up the comet. As a result, a fiery tail of dust is formed. This debris and dust is part of the trail that we see in the sky when we observe the movement of comets.

What determines the shape of a comet's tail

The comet post below will help you better understand what comets are and how they work. They are different - with tails of various shapes. It's all about the natural composition of the particles that make up this or that tail. Very small particles quickly fly away from the Sun, and those that are larger, on the contrary, tend to the star. What is the reason? It turns out that the former move away, pushed by solar energy, while the latter are affected by the gravitational force of the Sun. As a result of these physical laws, we get comets whose tails are curved in various ways. Those tails, which are mostly composed of gases, will be directed away from the star, and corpuscular (consisting mainly of dust), on the contrary, will tend to the Sun. What can be said about the density of a comet's tail? Usually cloud tails can be measured in millions of kilometers, in some cases hundreds of millions. This means that, unlike the body of a comet, its tail consists mostly of rarefied particles, having almost no density. When an asteroid approaches the Sun, the comet's tail can split in two and become complex.

Particle speed in a comet tail

Measuring the speed of movement in the tail of a comet is not so easy, since we cannot see individual particles. However, there are cases when the velocity of matter in the tail can be determined. Sometimes gas clouds can condense there. From their movement, you can calculate the approximate speed. So, the forces moving the comet are so great that the speed can be 100 times greater than the attraction of the Sun.

How much does a comet weigh

The entire mass of comets largely depends on the weight of the comet's head, or rather, its nucleus. Supposedly, a small comet can weigh only a few tons. Whereas, according to forecasts, large asteroids can reach a weight of 1,000,000,000,000 tons.

What are meteors

Sometimes one of the comets passes through the orbit of the Earth, leaving behind a trail of debris. When our planet passes over the place where the comet was, these debris and cosmic dust left from it enter the atmosphere with great speed. This speed reaches more than 70 kilometers per second. When the fragments of the comet burn up in the atmosphere, we see a beautiful trail. This phenomenon is called meteors (or meteorites).

Age of comets

Fresh asteroids of huge size can live in space for trillions of years. However, comets, like any other, cannot exist forever. The more often they approach the Sun, the more they lose the solid and gaseous substances that make up their composition. "Young" comets can drop in weight very much until a kind of protective crust forms on their surface, which prevents further evaporation and burnout. However, the "young" comet is aging, and the nucleus is decrepit and losing its weight and size. Thus, the surface crust acquires many wrinkles, cracks and breaks. Gas flows, burning, push the body of the comet forward and forward, giving speed to this traveler.

Comet Halley

Another comet, similar in structure to the Churyumov-Gerasimenko comet, is an asteroid discovered. He realized that comets have long elliptical orbits along which they move with a large time interval. He compared the comets that were observed from the earth in 1531, 1607 and 1682. It turned out that it was the same comet, which moved along its trajectory through a period of time equal to approximately 75 years. In the end, she was named after the scientist himself.

Comets in the solar system

We are in the solar system. At least 1000 comets have been found not far from us. They are divided into two families, and they, in turn, are divided into classes. To classify comets, scientists take into account their characteristics: the time it takes for them to travel all the way in their orbit, as well as the period from circulation. Taking Halley's comet, mentioned earlier, as an example, it takes less than 200 years to complete one revolution around the sun. It belongs to periodic comets. However, there are those that cover the entire path in much shorter periods of time - the so-called short-period comets. We can be sure that in our solar system there are a huge number of periodic comets that orbit around our star. Such celestial bodies can move so far from the center of our system that they leave behind Uranus, Neptune and Pluto. Sometimes they can get very close to the planets, because of which their orbits change. An example is

Comet Information: Long Period

The trajectory of long-period comets is very different from short-period comets. They go around the Sun from all sides. For example, Heyakutake and Hale-Bopp. The latter looked very spectacular when they last approached our planet. Scientists have calculated that the next time from Earth they can be seen only after thousands of years. A lot of comets, with a long period of movement, can be found at the edge of our solar system. Back in the middle of the 20th century, a Dutch astronomer suggested the existence of a cluster of comets. After a while, the existence of a comet cloud was proved, which is known today as the "Oort Cloud" and was named after the scientist who discovered it. How many comets are in the Oort Cloud? According to some assumptions, not less than a trillion. The period of movement of some of these comets can be several light years. In this case, the comet will cover its entire path in 10,000,000 years!

Fragments of Comet Shoemaker-Levy 9

Reports of comets from all over the world help in their study. A very interesting and impressive vision could be observed by astronomers in 1994. More than 20 fragments left from the comet Shoemaker-Levy 9 collided with Jupiter at a crazy speed (approximately 200,000 kilometers per hour). Asteroids flew into the planet's atmosphere with flashes and huge explosions. The incandescent gas influenced the formation of very large fiery spheres. The temperature to which the chemical elements warmed up was several times higher than the temperature that is recorded on the surface of the Sun. After that, telescopes could see a very high column of gas. Its height reached enormous proportions - 3200 kilometers.

Comet Biela - double comet

As we have already learned, there is plenty of evidence that comets break down over time. Because of this, they lose their brightness and beauty. We can consider only one example of such a case - Biela's comets. It was first discovered in 1772. However, subsequently it was noticed more than once again in 1815, after - in 1826 and in 1832. When it was observed in 1845, it turned out that the comet looks much larger than before. Six months later, it turned out that it was not one, but two comets that were walking next to each other. What happened? Astronomers have determined that a year ago the Biela asteroid split in two. The last time scientists recorded the appearance of this miracle comet. One part of it was much brighter than the other. She was never seen again. However, after a while, a meteor shower was more than once striking, the orbit of which exactly coincided with the orbit of Biela's comet. This case proved that comets are capable of collapsing over time.

What happens in a collision

For our planet, a meeting with these celestial bodies does not bode well. A large fragment of a comet or meteorite about 100 meters in size exploded high in the atmosphere in June 1908. As a result of this disaster, many reindeer died and two thousand kilometers of taiga were knocked down. What would happen if such a block exploded over a large city such as New York or Moscow? It would cost the lives of millions of people. And what would happen if a comet with a diameter of several kilometers hit the Earth? As mentioned above, in mid-July 1994, it was “fired upon” by debris from the comet Shoemaker-Levy 9. Millions of scientists watched what was happening. How would such a collision end for our planet?

Comets and the Earth - the views of scientists

Information about comets known to scientists sows fear in their hearts. Astronomers and analysts draw terrible pictures in their minds with horror - a collision with a comet. When an asteroid hits the atmosphere, it will cause destruction inside the cosmic body. It will explode with a deafening sound, and on Earth it will be possible to observe a column of meteorite fragments - dust and stones. The sky will be engulfed in a fiery red glow. There will be no vegetation left on Earth, because due to the explosion and fragments, all forests, fields and meadows will be destroyed. Due to the fact that the atmosphere will become impervious to sunlight, it will become sharply cold, and plants will not be able to perform the role of photosynthesis. Thus, the nutrition cycles of marine life will be disrupted. Being without food for a long time, many of them will die. All of the above events will affect the natural cycles. Widespread acid rain will have a detrimental effect on the ozone layer, making it impossible to breathe on our planet. What happens if a comet falls into one of the oceans? Then it can lead to devastating environmental disasters: the formation of tornadoes and tsunamis. The only difference will be that these cataclysms will be much larger than those that we could experience for ourselves over several thousand years of human history. Huge waves of hundreds or thousands of meters will sweep away everything in their path. There will be nothing left of towns and cities.

"Don't Worry"

Other scientists, on the contrary, say that there is no need to worry about such cataclysms. According to them, if the Earth comes close to a celestial asteroid, then this will only lead to sky lighting and meteor showers. Should we worry about the future of our planet? Is there any chance that we will ever be met by a flying comet?

Comet fall. Should I be afraid

Can you trust everything scientists present? Do not forget that all the information about comets recorded above is just theoretical assumptions that cannot be verified. Of course, such fantasies can sow panic in the hearts of people, but the likelihood that something like this will ever happen on Earth is negligible. Scientists who explore our solar system admire how thoughtful everything is in its design. It is difficult for meteorites and comets to reach our planet because it is protected by a giant shield. The planet Jupiter, due to its size, has a huge gravity. Therefore, it often protects our Earth from asteroids and comet remnants flying by. The location of our planet leads many to believe that the whole device was thought out and designed in advance. And if this is so, and you are not a zealous atheist, then you can sleep peacefully, because the Creator will undoubtedly preserve the Earth for the purpose for which he created it.

The names of the most famous

Reports on comets from various scientists around the world form a huge database of information about cosmic bodies. Among the most famous, there are several. For example, comet Churyumov - Gerasimenko. In addition, in this article we could get acquainted with the comet Fumaker-Levy 9 and the comets Encke and Halley. In addition to them, Sadulaev's comet is known not only to researchers of the sky, but also to lovers. In this article, we have tried to provide the most complete and verified information about comets, their structure and contact with other celestial bodies. However, just as it is impossible to embrace all the expanses of space, it will not be possible to describe or list all comets known at the moment. Brief information about the comets of the solar system is presented in the illustration below.

sky exploration

The knowledge of scientists, of course, does not stand still. What we know now was not known to us some 100 or even 10 years ago. We can be sure that man's tireless desire to explore the expanses of space will continue to push him to try to understand the structure of celestial bodies: meteorites, comets, asteroids, planets, stars and other more powerful objects. Now we have penetrated into such expanses of space that thinking about its immensity and unknowability plunges one into awe. Many agree that all this could not have appeared by itself and without a purpose. Such a complex structure must have an intention. However, many questions related to the structure of the cosmos remain unanswered. It seems that the more we learn, the more reason to explore further. In fact, the more information we acquire, the more we realize that we do not know our solar system, our Galaxy, and even more so the Universe. However, all this does not stop astronomers, and they continue to struggle further on the mysteries of life. Every nearby comet is of particular interest to them.

Computer program “Space Engine”

Fortunately, today not only astronomers can explore the Universe, but also ordinary people, whose curiosity encourages them to do so. Not so long ago, a program for computers “Space Engine” was released. It is supported by most modern mid-range computers. It can be downloaded and installed completely free of charge using a search on the Internet. Thanks to this program, information about comets for children will also be very interesting. It presents a model of the entire universe, including all comets and celestial bodies that are known to modern scientists today. To find a space object of interest to us, for example, a comet, you can use the oriented search built into the system. For example, you need the Churyumov-Gerasimenko comet. In order to find it, you must enter its serial number 67 R. If you are interested in another object, for example, Sadulaev's comet. Then you can try to enter its name in Latin or enter its special number. Thanks to this program, you can learn more about space comets.

In 2009, Robert McNaught opened Comet C/2009 R1, which is approaching the Earth, and in mid-June 2010, the inhabitants of the northern hemisphere will be able to see it with the naked eye.

Comet Morehouse(C / 1908 R1) - a comet discovered in the USA in 1908, which was the first of the comets to be actively studied using photography. Amazing changes were seen in the structure of the tail. During the day of September 30, 1908, these changes occurred continuously. On October 1, the tail broke off and could no longer be observed visually, although a photograph taken on October 2 showed three tails. The rupture and subsequent growth of the tails occurred repeatedly.

Comet Tebbutt(C/1861 J1) - A bright comet, visible to the naked eye, was discovered by an Australian amateur astronomer in 1861. The Earth passed through the comet's tail on June 30, 1861.

Comet Hyakutake(C/1996 B2) is a large comet that reached magnitude zero in March 1996 and produced a tail estimated to be at least 7 degrees long. Its apparent brightness is largely due to its proximity to the Earth - the comet passed from it at a distance of less than 15 million km. The maximum approach to the Sun is 0.23 AU, and its diameter is about 5 km.

Comet Humason(C / 1961 R1) - a giant comet, discovered in 1961. Its tails, despite being so far from the Sun, still extend 5 AU in length, which is an example of unusually high activity.

Comet McNaught(C/2006 P1), also known as the Great Comet of 2007, is a long-period comet discovered on August 7, 2006 by British-Australian astronomer Robert McNaught and has become the brightest comet in the last 40 years. Residents of the northern hemisphere could easily observe it with the naked eye in January and February 2007. In January 2007, the comet's magnitude reached -6.0; The comet was visible everywhere in daylight, and the maximum length of the tail was 35 degrees.

Halley's comet is undoubtedly the most popular of the comets. With amazing constancy, approximately every 76 years, it appears nearby, and every time for 22 centuries, earthlings have recorded this rare event. Let us clarify that the period of revolution of a comet around varies from 74 to 79 years, so 76 years is the average period for the past centuries.

Not all appearances of Halley's comet in the earth's sky were remarkable. Sometimes, however, the brightness of its core exceeded the brightness of Venus during the period of the best visibility of the planet. In such cases, the comet's tails became long and spectacular, and the records in the annals reflected the excitement of observers caused by the "ominous" tailed star. In other years, the comet looked like a dim, hazy star with a small tail, and then the records in the chronicles were very short.

Over the past 2000 years, Halley's Comet has never approached the Earth closer than 6 million km. Approach to the Earth in 1986. was the most unfavorable in the entire history of observations of the comet - the conditions for its visibility from Earth were the worst.

For those who have never seen a real comet, but judge the appearance of comets from drawings in books, we will inform you that the surface brightness of cometary tails never exceeds the brightness of the Milky Way. Therefore, in the conditions of any large modern city, it is no easier to see a comet than the Milky Way. At best, it is possible to consider its core in the form of a more or less bright, slightly foggy and somewhat “smeared” star. But where the sky is clear, its background is black, and the scattering of stars of the Milky Way is clearly visible, a large comet with bright tails is, of course, an unforgettable sight.

Not all people manage to see the passage of Halley's comet near the Earth twice in their lives. Still, 76 years is a long period, close to the average duration of human life, and therefore the list of famous people who twice observed the return of Halley's comet is not so long.

Among them we find Johann Galle (1812-1910) - the astronomer who discovered the planet Neptune according to W.'s predictions, Caroline Herschel (1750 -1848) - the sister of the famous founder of stellar astronomy, Leo Tolstoy (1828-1910) and others. It is curious that the famous American writer Mark Twain was born two weeks after the appearance of Halley's comet in 1835, and died the day after its next closest approach to the Sun in 1910. Shortly before this, Mark Twain jokingly told his friends that since he was born in the year of the next appearance of Halley's comet, he would die immediately after her next return!

It is interesting to trace how the Earth met the famous comet throughout the history of its observations. Only in 1682. suspected that they were dealing with a periodic comet. In 1759 this suspicion was confirmed. But this year, as well as the next visit of the comet in 1835, astronomers were able to make only telescopic observations of this cosmic body, which said little about its physical nature. Only in 1910. scientists met Halley's comet fully armed. The comet flew near the Earth, hitting it (in May 1910) with its tail. It was very convenient to observe it from the Earth, and photography, spectroscopy and photometry were already in service with astronomers.

By that time, the great Russian researcher of comets, Fyodor Alexandrovich (1831-1904), had created a mechanical theory of cometary forms, and his followers were able to successfully apply the new theory to the interpretation of observed cometary phenomena. In general, the previous meeting with Halley's comet in 1910. can be called a celebration of cometary astronomy. At this time, the foundations of the modern physical theory of comets were laid, and it would not be an exaggeration to say that the current ideas about comets are largely due to the successes of 1910.

On its thirtieth return to the Sun, Halley's comet was in 1986. met unusually. For the first time, spacecraft flew to the comet in order to explore it in close proximity. Soviet scientists headed by academician R.Z. Sagdeev developed and implemented the Vega project - sending special interplanetary stations Vega-1 and Vega-2 to the comet. Their task included photographing the nucleus of Halley's comet at close range and studying the processes occurring in it. The European project "Giotto" and the Japanese projects "Planet-A" and "Planet-B" were also included in the international program of research on Halley's comet, which began to be developed as early as 1979.

Now it is pleasant to state that this program has been successfully completed, and in the course of its implementation fruitful international cooperation of scientists from different countries has been manifested. So, for example, during the implementation of the Giotto program, American specialists helped restore normal communication with the station, and later Soviet scientists ensured its flight at a given distance from the cometary nucleus.

Astronomical tracking stations were of considerable use in receiving information from stations flying near Halley's comet. Now, by joint efforts, we can imagine what Halley's comet is and what, therefore, comets are in general. The main part of the comet - its nucleus - is an elongated body of irregular shape with dimensions of 14x7.5x7.5 km. It rotates around its axis with a period of about 53 hours. This is a huge block of polluted ice, where small solid particles of a silicate nature are included as “pollutions”.

Recently in the press for the first time appeared a comparison of the nucleus of Halley's comet with a dirty March snowdrift, in which the mud crust protects the snowdrift from rapid evaporation. Something of this kind also occurs in a comet - under the influence of sunlight, the ice component sublimates and, in the form of gas streams, moves away from the nucleus, which very weakly attracts all objects to itself. These streams of gases also carry away solid dust, which forms the dust tails of the comet.

The apparatus "Vega-1" found that every second 5 - 10 tons of dust are ejected from the core - some of it still remains, covering the icy core with a protective dust crust; Because of this crust, the reflectivity (albedo) of the core is markedly reduced and the surface temperature of the core is quite high. Water is constantly evaporating from a comet near the Sun, which can explain the presence of a hydrogen corona in comets. In general, the "ice model" of the nucleus was brilliantly confirmed, which has now become a fact from a hypothesis. The size of Halley's comet is so small that its nucleus could easily be placed on the territory of Moscow inside the ring road. Once again, humanity was convinced that comets are small bodies that are in a state of continuous destruction.

Meeting in 1986 was very successful for science, and now we will meet with Halley's comet only in 2061.

The life of comets is relatively short - even the largest of them is able to complete only a few thousand revolutions around the Sun. After this period, the comet's nucleus completely disintegrates. But such a decay occurs gradually, and therefore, during the life of a comet, a plume is formed along the entire orbit from the decay products of its nucleus, resembling a donut. That is why every time when meeting with such a "donut" a large number of "shooting stars" flies into the earth's atmosphere - meteor bodies generated by a decaying comet. Then they talk about the meeting of our planet with a meteor shower.

Twice a year, in May and October, the Earth passes through a "meteor donut" generated by the nucleus of Halley's comet. In May, meteors fly out of the constellation of Aquarius, in October - from the constellation of Orion.

http://www.astronos.ru/2-5.html

In our solar system, along with the planets and their satellites, there are space objects that are of great interest in the scientific community and are popular among the inhabitants. A place of honor in this series is rightfully occupied by comets. It is they who add brightness and dynamics to the solar system, turning near space into a testing ground for a short time. The appearance of these space wanderers in the sky is always accompanied by bright astronomical phenomena that even an amateur astronomer can observe. The most famous space guest is Halley's comet, a space object that regularly visits near-Earth space.

The last appearance of Halley's comet in our near space was in February 1986. She appeared for a short moment in the sky in the constellation of Aquarius and quickly disappeared into the halo of the solar disk. During the passage of perihelion in 1986, the space guest was in the field of view from the Earth and a short period could be observed. The next visit of the comet should take place as early as 2061. Will the usual schedule for the appearance of the most famous space visitor after 76 years be violated, will the comet fly back to us in all its glory and splendor?

When did Halley's comet become known to man?

The frequency of occurrence of known comets in the solar system does not exceed 200 years. The visits of such guests have always evoked an ambiguous reaction in a person, causing concern to some unenlightened people and delighting the scientific fraternity.

For other comets, visits to our solar system are rare. Such objects fly into our near space with a frequency of more than 200 years. It is not possible to calculate their exact astronomical data due to their rare occurrence. In both cases, humanity has constantly dealt with comets throughout its existence.

For a long time, man was in the dark about the nature of this astrophysical phenomenon. Only at the beginning of the 18th century was it possible to initiate a systematic study of these most interesting space objects. Halley's comet, discovered by the English astronomer Edmund Halley, became the first celestial body about which it was possible to obtain reliable information. This became possible due to the fact that this space wanderer is clearly visible to the naked eye. Using the observational data of his predecessors, Halley was able to identify a space guest who had visited the solar system three times before. According to his calculations, the same comet appeared in the night sky in 1531, in 1607 and in 1682.

It is today that astrophysicists, using the nomenclature of comets and the available information about their parameters, can confidently say that the appearance of Halley's comet was noted in the earliest sources, approximately in 240 BC. Judging by the descriptions available in the Chinese chronicles and in the manuscripts of the Ancient East, the Earth has already met this comet more than 30 times. The merit of Edmund Halley lies in the fact that it was he who managed to calculate the periodicity of the appearance of a space guest and quite accurately predict the next appearance of this celestial body in our night sky. According to him, the next visit was to take place in 75 years, at the end of 1758. As expected by the English scientist, in 1758 the comet once again visited our night sky and by March 1759 flew within sight. This was the first predicted astronomical event associated with the existence of comets. From that moment on, our constant celestial guest was named after the famous scientist who discovered this comet.

On the basis of long-term observations of this object, the dates of its subsequent appearances are approximately drawn up. Despite the fact that in comparison with the transience of human life, the period of revolution of Halley's comet is quite long (74-79 Earth years), scientists are always looking forward to the next visit of the space wanderer. In the scientific community, it is considered great luck to observe this enchanting flight and the astrophysical phenomena that accompany it.

Astrophysical features of the comet

In addition to its rather frequent appearance, Halley's comet has interesting features. This is the only well-studied cosmic body that, at the moment of approach to the Earth, moves with our planet on a collision course. The same parameters are observed in relation to the motion of other planets in our star system. Hence, there are quite ample opportunities for observing a comet that makes its flight in the opposite direction along a highly elongated elliptical orbit. The eccentricity is 0.967 e and is one of the highest in the solar system. Only Nereid, a moon of Neptune, and the dwarf planet Sedna have orbits with such similar parameters.

The elliptical orbit of Halley's comet has the following characteristics:

• the length of the semi-major axis of the orbit is 2.667 billion km;
• at perihelion, the comet moves away from the Sun at a distance of 87.6 million km;
• during the passage of Halley's comet near the Sun at aphelion, the distance to our star is 5.24 billion km;
• the comet's orbital period according to the Julian calendar averages 75 years;
• the speed of Halley's comet in orbit is 45 km/s.

All the above data on the comet became known as a result of observations made over the past 100 years, from 1910 to 1986. Due to the large elongation of the orbit, our guest flies past us at a huge oncoming speed - 70 kilometers per second, which is an absolute record among the space objects of our solar system. Halley's comet of 1986 provided the scientific community with a lot of detailed information about its structure and physical characteristics. All data obtained was obtained by direct contact of automatic probes with a celestial object. Research was carried out with the help of the Vega-1 and Vega-2 spacecraft, specially launched for a close acquaintance with the space guest.

Automatic probes made it possible not only to obtain information about the physical parameters of the nucleus, but also to study in detail the shell of a celestial body and get an idea of ​​​​what the tail of Halley's comet is.

In terms of its physical parameters, the comet was not as large as previously thought. The size of an irregularly shaped cosmic body is 15x8 km. The greatest length is 15 km. with a width of 8 km. The mass of the comet is 2.2x1024 kg. By its size, this celestial body can be equated to medium-sized asteroids wandering in the space of our solar system. The density of the space wanderer is 600 kg/m3. For comparison, the density of water in the liquid state is 1000 kg/m3. Data on the density of a comet's nucleus vary depending on its age. The latest data is the result of observations made during the last visit of the comet in 1986. It is not a fact that in 2061, when the next arrival of a celestial body is expected, its density will be the same. The comet is constantly losing weight, collapsing, and may eventually disappear.

Like all space objects, Halley's comet has its own albedo of 0.04, comparable to the albedo of charcoal. In other words, the nucleus of a comet is a rather dark cosmic object with a weak surface reflectivity. Sunlight barely reflects off the comet's surface. It becomes visible only due to its rapid movement, which is accompanied by a bright and spectacular effect.

During its flight through the expanses of the solar system, the comet is accompanied by the Aquarids and Orionids meteor showers. These astronomical phenomena are natural products of the destruction of the comet's body. The intensity of both phenomena can increase with each successive passage of the comet.

Versions about the origin of Halley's comet

In accordance with the accepted classification, our most popular space guest is a short-period comet. These celestial bodies are characterized by a small inclination of the orbit with respect to the axis of the ecliptic (only 10 degrees) and a short period of revolution. As a rule, such comets belong to the Jupiter family of comets. Against the background of these space objects, Halley's comet, like other similar space objects, stands out strongly for its astrophysical parameters. As a result, such objects were assigned to a separate, Halley type. At the moment, scientists could detect only 54 comets of the same type as Halley's comet, which in one way or another visit near-Earth space throughout the entire existence of the solar system.

There is an assumption that such celestial bodies were previously long-period comets and moved to another class only due to the influence of the force of attraction of the giant planets: Jupiter, Saturn, Uranus and Neptune. In this case, our current regular guest could have formed in the Oort cloud - the out-of-bounds region of our solar system. There is also a version about a different origin of Halley's comet. The formation of comets is allowed in the boundary region of the solar system, where trans-Neptunian objects are located. In many astrophysical parameters, small bodies in this region are very similar to Halley's comet. We are talking about the retrograde orbit of objects, strongly reminiscent of the orbit of our space guest.

Preliminary calculations showed that the celestial body that comes to us every 76 years has existed for more than 16,000 years. At least the comet has been moving in its current orbit for quite some time. It is not possible to state whether the orbit was the same for 100-200 thousand years. A flying comet is constantly influenced not only by the forces of gravity. Due to its nature, this object is strongly affected by mechanical stress, which in turn causes a reactive effect. For example, when a comet is at aphelion, the sun's rays heat up its surface. In the process of heating the surface of the core, sublimating gas flows arise, acting like rocket engines. At this moment, the comet's orbit fluctuates, affecting the deviations in the period of revolution. These deviations are clearly visible already at perihelion and can be 3-4 days.

Soviet robotic spacecraft and vehicles of the European Space Agency during their trip to Halley's comet in 1986 almost missed. Under terrestrial conditions, it turned out to be impossible to predict and calculate possible deviations in the period of revolution of a comet, which caused oscillations of a celestial body in orbit. This fact confirmed the version of scientists that the period of revolution of Halley's comet may change in the future. In this aspect, the composition and structure of comets become interesting. The preliminary version that these are huge blocks of cosmic ice is refuted by the long existence of comets that have not disappeared or evaporated in outer space.

Composition and structure of a comet

The nucleus of Halley's comet was first studied at close range by automatic space probes. If earlier a person could observe our guest only through a telescope, viewing her at a distance of 28 06 AU. That is, now the pictures were obtained from a minimum distance of just over 8000 km.

In fact, it turned out that the nucleus of a comet is relatively small and in appearance resembles an ordinary potato tuber. Examining the density of the core, it becomes clear that this cosmic body is not a monolith, but is a pile of fragments of cosmic origin, closely connected by gravitational forces into a single structure. A giant stone block does not just fly in outer space, tumbling in different directions. The comet has a rotation, which, according to various sources, is 4-7 days. Moreover, the rotation is directed towards the movement of the comet in orbit. Judging by the images, the core has a complex relief, which includes depressions and hills. A crater of cosmic origin was even discovered on the surface of the comet. Even despite the small amount of information obtained from the images, it can be assumed that the comet's nucleus is a large fragment of another large cosmic body that once existed in the Oort cloud.

The comet was first photographed in 1910. At the same time, data were obtained from a spectral analysis of the composition of our guest's coma. As it turned out, during the flight, as it approaches the Sun, volatile substances, represented by frozen gases, begin to evaporate from the heated surface of a celestial body. Vapors of nitrogen, methane and carbon monoxide are added to the water vapor. The intensity of emission and evaporation leads to the fact that the size of the coma of Halley's comet exceeds the size of the comet itself by a thousand times - 100 thousand km. against 11 km of average size. Together with the evaporation of volatile gases, dust particles and small fragments of the comet's nucleus are released. Atoms and molecules of volatile gases refract sunlight, forming the effect of fluorescence. Dust and large fragments scatter reflected sunlight into outer space. As a result of ongoing processes, the coma of Halley's comet is the brightest element of this celestial body, which ensured its good visibility.

Do not forget about the comet's tail, which has a special shape for a comet and is its trademark.

Three types of comet tails should be distinguished:

• type I comet tail (ionic);
• comet tail type II;
• type III tail.

Under the influence of the solar wind and radiation, the ionization of the substance that creates the coma occurs. Charged ions under the pressure of the solar wind are pulled into a long tail, the length of which exceeds hundreds of millions of kilometers. The slightest fluctuations in the solar wind or a decrease in the intensity of solar radiation leads to a partial tail break. Often, such processes can lead to the complete disappearance of the tail of a space wanderer. Astronomers observed this phenomenon with Halley's comet in 1910. Due to the huge difference in the speed of movement of charged particles that make up the comet's tail, and the orbital speed of a celestial body, the direction of development of the comet's tail is located strictly in the opposite direction from the Sun.

As for solid fragments, cometary dust, the influence of the solar wind is not so significant here, so the dust spreads at a speed obtained as a result of a combination of the acceleration imparted by the pressure of the solar wind to the particles and the initial orbital velocity of the comet. As a result, the dust tails lag far behind the ion tail, forming separate type II and III tails directed at an angle to the direction of the comet's orbit.

In terms of their intensity and frequency of ejection, the dust tails of a comet are a short-term phenomenon. If the ion tail of a comet, when fluorescing, gives a violet glow, then the dust tails of types II and III have a reddish tint. Our guest is characterized by the presence of tails of all three types. Astronomers are familiar with the first two quite well, while the tail of the third type was noticed only in 1835. On its last visit, Halley's comet rewarded astronomers with the opportunity to observe two tails: the first and second types.

Analysis of the behavior of Halley's Comet

Judging by the observations made during the last visit of the comet, the celestial body is a fairly active space object. The side of the comet facing the Sun at a certain moment is a boiling source. The temperature on the surface of the comet facing the Sun varies in the range of 30-130 degrees with a plus sign on the Celsius scale, while the temperature on the rest of the comet's nucleus drops to below 100 degrees. Such a discrepancy in temperature readings speaks in favor of the fact that only a small part of the comet's nucleus has a high albedo and can heat up quite strongly. The remaining 70-80% of its surface is covered with a dark substance and absorbs sunlight.

Such studies have suggested that our bright and dazzling guest is actually a lump of dirt mixed with cosmic snow. The main mass of cosmic gases is water vapor (more than 80%). The remaining 17% are carbon monoxide, particles of methane, nitrogen and ammonia. Only 3-4% is carbon dioxide.

As for cometary dust, it mainly consists of carbon-nitrogen-oxygen compounds and silicates, which form the basis of the terrestrial planets. The study of the composition of the water vapor emitted by the comet put an end to the theory of the cometary origin of the Earth's oceans. The amount of deuterium and hydrogen in the nucleus of Halley's comet turned out to be much greater than their amount in the earth's water.

If we talk about how much this lump of dirt and snow has enough material for life, then here you can consider Halley's comet from different angles. Scientists' calculations, based on data on 46 comet appearances, speak in favor of the fact that the life of a celestial body is chaotic and constantly changing depending on external conditions. In other words, throughout its existence, the comet is in a state of dynamic chaos.

Presumably, the duration of the existence of Halley's comet is estimated at 7-10 billion years. Calculating the amount of matter lost during the last visit to our near-Earth space, scientists concluded that the comet's nucleus has already lost up to 80% of its original mass. It can be assumed that now our guest is at an advanced age and in a few millennia will fall apart into small fragments. The finale of this brightest life can happen within the solar system, in front of us, or, conversely, take place in the backyards of our common home.

Finally

The last visit of Halley's comet, which took place in 1986 and was expected for so many years, was the greatest disappointment for many. The main reason for the massive disappointment was the inability to observe a celestial body in the northern hemisphere. All preparations for the upcoming event went down the drain. On top of that, the period of observation of the comet turned out to be very short. This has led to the fact that few observations have been made by scientists around the world. A few days later, the comet disappeared behind the solar disk. The next meeting with the space guest has been postponed for 76 years.

HALLEY'S COMET, the only one of the short-period comets (orbital period approx. 76 years), easily accessible for observation with the naked eye.

Relatively small nuclei of comets, consisting of ice interspersed with dust particles, approaching the Sun, are enveloped in a huge atmosphere (coma) of gas and dust hundreds of thousands of kilometers long. Intense solar heating vaporizes ice from the comet's nucleus, expelling gas and dust into its surrounding atmosphere. Then, under the pressure of solar photons and high-speed particles of the solar wind, this substance flies away in the opposite direction from the Sun, forming a gas-dust comet tail, reaching a length of millions of kilometers.

In March 1986, Halley's comet was observed not only by numerous amateur astronomers and professional scientists, but also by five international spacecraft ( see also SPACE PROBE). The Japanese probes Sakigake and Suisei observed a huge hydrogen cloud surrounding the comet and studied the interaction of the comet with charged particles of the solar wind. The Soviet probes "Vega-1 and -2" passed on March 6 and 9 at distances of 8,871 and 8,014 km from the comet. On March 14, 1986, the Giotto probe of the European Space Agency passed closest to the comet's nucleus - only 605 km. Television images transmitted by European and Soviet probes showed the comet's pitch black nucleus. Comparing ground and space observations of gas and dust surrounding the core, scientists concluded that it is about 50% ice, and the rest is dust and other non-volatile substances. Ice is composed primarily of water (80%) and carbon monoxide (10%), with the remainder being formaldehyde, carbon dioxide, methane, ammonia and hydrocyanic acid. The non-volatile part, mainly represented by micron-sized dust particles, consists of either rocky matter or light hydrocarbons.

Externally, the nucleus of Halley's comet is a potato-shaped object measuring approx. 14ґ 10ґ 8 km. Its very black crust of carbonaceous (organic) matter is in many places covered with faults, through which the subcrustal substance is visible, consisting mainly of water ice interspersed with dark dust grains. Since the comet's nucleus rotates around its axis with a period of several days, this ice evaporates under the influence of sunlight and turns into gas, which, flying out of the nucleus, captures dust particles with it. It was this core, like a small, dirty iceberg, that supplied all the gas and dust that formed the vast atmosphere and tail of the comet.

Halley's comet was the first to be predicted to return periodically to the central region of the solar system. Using the mathematical apparatus developed by I. Newton, his colleague E. Halley (1656–1742) calculated the parameters of the orbits of 24 comets observed by astronomers in previous years. It turned out that the comets that appeared in 1531, 1607 and 1682 had similar orbits. Halley suggested that in reality it was one and the same object, and predicted that the comet now bearing his name would return to the Sun at the end of 1758 or at the beginning of 1759. When at the end of 1758 the German amateur astronomer I. Palich discovered the comet in the sky, this was a triumph for Halley's calculations and Newton's underlying laws.

On its long path along the orbit, Halley's comet falls under the influence of the gravitational attraction of the planets it passes by, and approaching the Sun, it feels a weak force return from the gases evaporating from the surface of its nucleus. Under the influence of these perturbations, the orbital period of a comet can change for several years from one of its appearances to another. Calculating the past motion of Halley's Comet allows us to calculate each of its 30 appearances between 240 B.C. and 1986. Its next two solar transits are expected on July 28, 2061 and March 27, 2134. The comet's 1986 flyby was a bit of a disappointment to observers because it didn't get close enough to Earth. Its minimum distance from our planet on April 10, 1986 was 63 million km. Unfortunately, during the return in 2061, the comet will not come closer to the Earth than 71 million km. This will happen on July 29, 2061. And the return of 2134 will be more impressive, since the comet on May 7, 2134 will be at a distance of 13.7 million km from the Earth.