These "tailed" inhabitants of the solar system are comets. The very name of the comet in Greek means "hairy", "shaggy". In ancient Greece, and later in the Middle Ages, comets were usually depicted as severed heads with flying hair.

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She was visible in March 2002. It is famous, in particular, for the fact that it was visible in the sky near the famous galaxy of the Andromeda Nebula.

Comets are shapeless cosmic bodies in the solar system. They move in highly elongated elliptical orbits. Many comets have a very long period of revolution by human standards and is more than 200 years. Such comets are called long-period comets. Comets with a period of less than 200 years are called short-period comets. Currently, several dozen long-period and more than 400 short-period comets are known.

Comet orbit compared to planetary orbits

These space objects have an insignificant mass and do not reveal themselves in anything far from the Sun. Comets consist of a stone or metal core enclosed in an icy shell of frozen gases (carbon dioxide, ammonia). As it approaches the Sun, the comet begins to evaporate, forming a "coma" - a cloud of dust and gas that surrounds the nucleus. Moreover, these substances of the comet pass into the gaseous state immediately from the solid, bypassing the liquid - such a phase transition is called sublimation. The nucleus and coma form the head of the planet. As it approaches the Sun, the gas cloud forms a huge gas plume - a tail tens or even hundreds of millions of kilometers long.

Light rays emanating from the Sun and streams of electrical particles deflect comet tails in the opposite direction from the luminary. The same solar wind causes the glow of rarefied gas in the tails of comets.

comet parts
Pay attention to two tails - dust and plasma

The bulk of the comet's mass is concentrated in its nucleus, but 99.9% of the light radiation comes from the tail, because the nucleus is very compact, and also has a low reflectivity.

Large comets can remain visible for several weeks. Having circled the Sun, they move away and disappear from the field of view. Many comets are observed regularly.

Comet McNaught.
This comet became a real sensation in January 2007. Bright, with a huge fan-shaped tail, she did not leave indifferent among those who were lucky enough to see her. But in all its glory, Comet McNaught was observed only in the southern hemisphere of the planet.

Comets attract everyone's attention. Their appearance in ancient times caused fear and was perceived as a heavenly sign of future terrible events.

Human history in antiquity was very rich in various tragic events, such as wars, epidemics, palace coups, assassinations of rulers. Some of these events were accompanied by the appearance of bright comets, and the predictors began to connect the phenomena of heaven and earth with each other.
This famous antique French tapestry from the time of William the Conqueror shows Halley's Comet as it appeared in 1066. That year there was a battle in which the duke defeated the army of the Anglo-Saxon king Harold II and took the English throne. This victory was then attributed to the influence of a heavenly sign - a comet. The inscription on the tapestry says - "marvel at the star."

In fact, the comet cannot have any noticeable impact on our planet because of its insignificant size: the mass of the comet is about a billion times less than the mass of the Earth, and the density of the tail matter is almost zero. So, in May 1910, the Earth passed through the tail of Halley's comet, but did not experience any changes.

The comet approached Jupiter in 1992 and was torn apart by its gravity. In July 1994, its fragments collided with Jupiter, causing fantastic effects in the planet's atmosphere.
The comet was discovered on March 24, 1993, when it was already a chain of fragments.

By their origin, comets are remnants of the primary matter of the solar system. Therefore, their study helps to restore the picture of the formation of planets, including the Earth.

The most famous comet is Halley's Comet.

Comet Halley

The orbital period of Halley's comet around the Sun is 76 years, the semi-major axis of the orbit is 17.8 AU. e, eccentricity 0.97, orbital inclination to the ecliptic plane 162.2°, perihelion distance 0.59 AU. e. The size of Halley's comet is 14 km long and 7.5 km across.

It was thanks to her that the English astronomer Edmund Halley discovered the periodicity of the appearance of comets. Comparing the parameters of the orbits of several bright comets of the past, he concluded that these were not different comets, but the same one, periodically returning to the Sun along a highly elongated path. He predicted the return of this comet, and his prediction was brilliantly confirmed. This comet was named after him.

From 239 BC Halley's comet has been observed 30 times. The last time it appeared in 1986 and the next time it will be observed in 2061. On the last visit of a space guest to our region, it was studied at close range by 5 interplanetary probes - two Japanese ("Sakigake" and "Suisei"), two Soviet ( "Vega-1" and "Vega-2") and one European ("Giotto").

Bibliographic description: Falkovskaya VD, Kosareva VN Comets and their research using spacecraft // Young scientist. - 2015. - No. 3. — S. 132-134..02.2019).



In this paper, I will tell you about comets and their research using spacecraft. First, let's look at the very definition of a comet. A comet is a small, nebulous celestial body that revolves around the Sun in a conic section with an extended orbit. When approaching the Sun, a comet forms a coma and sometimes a tail of gas and dust. It is believed that comets arrive in the solar system from the Oort cloud, which contains a huge number of cometary nuclei. Bodies, as a rule, consist of volatile substances that evaporate when approaching the Sun.

Comets are divided into short-period and long-period comets. At the moment, more than 400 short-period comets have been discovered. Many of them are included in the so-called families. For example, most of the shortest period comets (their full revolution around the Sun lasts 3–10 years) form the Jupiter family. A little smaller than the families of Saturn, Uranus and Neptune. Comets look like nebulous objects with trailing tails sometimes reaching millions of kilometers in length. The nucleus of a comet is a body of solid particles wrapped in a hazy shell called a coma. A nucleus with a diameter of several kilometers can have around it a coma 80,000 km across. Streams of sunlight knock gas particles out of the coma and throw them back, pulling them into a long smoky tail that follows her through space.

The brightness of comets is highly dependent on their distance from the Sun. Of all the comets, only a very small part approaches the Sun and the Earth enough to be seen with the naked eye. The structure of the comet. A comet consists of a nucleus, a coma and a tail. The nucleus of a comet is a solid part, in which almost all of its mass is concentrated. The most common is the Whipple model. According to this model, the core is a mixture of ice interspersed with particles of meteoric matter. With such a structure, layers of frozen gases alternate with dust layers. As the gases heat up, they carry clouds of dust with them. This makes it possible to explain the formation of gas and dust tails in comets. However, according to studies that were carried out using the American automatic station ‘Deep Impact’, the core consists of loose material and is a lump of dust with pores.

The coma is a light foggy shell surrounding the nucleus, consisting of gases and dust. It usually stretches from 100,000 to 1.4 million kilometers from the core. The coma, together with the nucleus, makes up the head of the comet. Coma is made up of three main parts:

a) Internal coma, where the most intense physical and chemical processes take place.

b) Visible coma.

c) Ultraviolet (atomic) coma.

In bright comets, as they approach the Sun, a ‘tail’ is formed - a luminous band, which, as a result of the solar wind, is directed in the opposite direction from the Sun. Comet tails vary in length and shape. For example, the tail of the 1944 comet was 20 million km long. The "Big Comet" of 1680 had a tail 240 million km long. There were also cases of separation of the tail from a comet (Comet Lulin). The tails of comets do not have sharp outlines and are almost transparent, as they are formed from rarefied matter. The composition of the tail is varied: gas or dust particles, or a mixture of both.

The theory of tails and forms of comets was developed by the Russian astronomer Fyodor Bredikhin. He also belongs to the classification of comet tails. Bredikhin proposed three types of comet tails:

a) straight and narrow, directed directly from the Sun;

b) wide and curved, deviating from the Sun;

c) short, strongly deviated from the central luminary.

The particles that make up comets have different compositions and properties and respond differently to solar radiation. Thus, the paths of these particles in space “diverge”, and the tails of space travelers take on different shapes. The speed of the particle is the sum of the speed of the comet and that acquired as a result of the action of the Sun. How far the comet's tail will differ from the direction from the Sun to the comet depends on the mass of the particles and the action of the Sun.

The study of comets. We all know that people have always taken a special interest in comets. Their unusual appearance and unexpected appearance served as a source of superstition. The ancients associated the appearance of these cosmic bodies in the sky with impending troubles and the onset of hard times. to the comet "Halley" of the spacecraft "Vega-1" and "Vega-2" and the European "Giotto". Numerous devices of these devices transmitted to Earth images of the comet's nucleus and information about its shell. It turned out that the nucleus of Halley's comet consists of ice, as well as dust particles. They form the shell of a comet, and as it approaches the Sun, some of them turn into a tail. The nucleus of Halley's comet has an irregular shape and rotates around an axis that is almost perpendicular to the plane of the comet's orbit.

At present, the study of the Churyumov-Gerasimenko comet is carried out using the Rosetta spacecraft. Let's take a closer look at the Rosetta spacecraft. The Rosetta spacecraft was designed and manufactured by the European Space Agency in collaboration with NASA. It consists of two parts: the Rosetta probe and the Fila descent vehicle. The spacecraft was launched on March 2, 2004 to the Churyumov-Gerasimenko comet. Rosetta is the first spacecraft to orbit a comet.

The work of the apparatus near the comet. In July 2014, Rosetta received the first data on the state of the Churyumov-Gerasimenko comet. The device determined that the comet's nucleus releases about 300 milliliters of water into the surrounding space every second. On August 3, 2014, an image with a resolution of 5.3 meters / pixel was obtained from a distance of 285 km. Images of the surface of the comet were obtained using the OSIRIS system (the scientific image processing system installed on Rosetta). At the beginning of September 2014, a map of the surface was compiled, highlighting several areas, each of which is characterized by a specific morphology. The presence of hydrogen and oxygen in the comet's coma was recorded.

On November 12, the ESA reported that the Philae spacecraft had undocked from the Rosetta probe and descended to the surface of the comet's nucleus. It took about seven hours. During this time, the device took pictures of both the comet itself and the Rosetta probe. Thus, on November 12, 2014, the world's first soft landing of a descent vehicle on the surface of a comet took place. On November 14, the Philae lander completed its main scientific tasks and transmitted all the results from scientific instruments to Earth through the Rosetta.

On November 15, Philae switched to power saving mode. The illumination of the solar batteries was too low to charge the batteries and perform communication sessions with the device. According to scientists, as the comet approached the Sun, the amount of energy generated should have increased to values ​​sufficient to turn on the apparatus.

On June 13, 2015, Philae exited the low power mode, communication with the device was established. On August 13, 2015, the Churyumov-Gerasimenko comet reached perihelion - the point of its closest approach to the Sun. This event has a symbolic meaning, since for the first time in the history of space exploration, an automatic station created by man passed along with the perihelion comet. At the point of closest approach to the Sun, the comet and the Rosetta station were at a distance of about 186 million km from our star. In this area, a space object appears once every six and a half years - this is how long the period of revolution of a comet around the Sun lasts. Now the Churyumov-Gerasimenko and Rosetta comets are moving at a speed of approximately 34.2 km / s. The pair is located at a distance of about 265.1 million km from the Earth. The Rosetta science program will last about another year - until September 2016. This will allow to collect a lot of important scientific information in addition to that already received. The European Space Agency said that the conditions necessary for the emergence of life have been found on the Churyumov-Gerasimenko comet.

The Philae probe found 16 organic compounds rich in carbon and nitrogen on the surface of the comet, including four compounds that had not previously been found on comets. Some of these compounds "play a key role in the synthesis of amino acids, sugars and nucleins," which are essential components for the origin of life, the ESA said in a statement. Formaldehyde, for example, is involved in the formation of ribose, a derivative of which is a component of DNA,” the agency said.

The presence of such complex molecules in a comet, scientists believe, suggests that chemical processes may have played a key role in helping shape the conditions for life to emerge. A hypothesis has been put forward, according to which microbes of alien origin may be present on the comet. It is the presence of living organisms under the ice that makes it possible to explain the black crust rich in organic compounds. It is impossible to confirm the theory, since neither the Rosetta nor the Philae were equipped with instruments that made it possible to search for traces of life.

The members of the Rosetta mission came to the conclusion that the Churyumov-Gerasimenko comet does not have its own magnetic field.

The study of the properties of comets should help researchers shed light on the processes that took place during the formation of objects in the solar system. In particular, the presence of a magnetic field in comets may be evidence that it was due to the magnetic interaction that the smallest particles united with each other. Meanwhile, the absence of its own magnetic field may force scientists to somewhat revise the accepted theory of the formation of objects in the solar system.

Literature:

1. Comet. https://ru.wikipedia.org/wiki/ %D0 %9A %D0 %BE %D0 %BC %D0 %B5 %D1 %82 %D0 %B0#.D0.98.D0.B7.D1.83. D1.87.D0.B5.D0.BD.D0.B8.D0.B5_.D0.BA.D0.BE.D0.BC.D0.B5.D1.82
2. Comet Churyumov-Gerasimenko reached perihelion http://www.3dnews.ru/918592?from=related-block
3. The work of the apparatus near the comet http://tunguska.ru/forum/index.php?topic=1019.0

The outer space around us is constantly in motion. Following the movement of galactic objects, such as galaxies and clusters of stars, other space objects, including astroids and comets, move along a well-defined trajectory. Some of them have been observed by humans for thousands of years. Along with the permanent objects in our sky, the Moon and planets, our sky is often visited by comets. Since the time of its appearance, mankind has repeatedly been able to observe comets, attributing a wide variety of interpretations and explanations to these celestial bodies. Scientists for a long time could not give clear explanations, observing the astrophysical phenomena that accompany the flight of such a swift and bright celestial body.

Characteristics of comets and their difference from each other

Despite the fact that comets are a fairly common phenomenon in space, not everyone was lucky to see a flying comet. The thing is that, by cosmic standards, the flight of this cosmic body is a frequent phenomenon. If we compare the period of revolution of such a body, focusing on Earth time, this is a rather large period of time.

Comets are small celestial bodies moving in outer space towards the main star of the solar system, our Sun. Descriptions of the flights of such objects observed from the Earth suggest that they are all part of the solar system, once participating in its formation. In other words, each comet is the remnants of cosmic material used in the formation of planets. Almost all known comets today are part of our star system. Like the planets, these objects obey the same laws of physics. However, their movement in space has its own differences and features.

The main difference between comets and other space objects is the shape of their orbits. If the planets move in the right direction, in circular orbits and lie in the same plane, then the comet rushes through space in a completely different way. This bright star, suddenly appearing in the sky, can move in the right direction or in the opposite direction, in an eccentric (elongated) orbit. Such movement affects the speed of the comet, which is the highest among all known planets and space objects in our solar system, second only to our main star.

The speed of Halley's comet when passing near the Earth is 70 km/s.

The plane of the comet's orbit does not coincide with the ecliptic plane of our system. Each celestial guest has its own orbit and, accordingly, its own period of revolution. It is this fact that underlies the classification of comets according to the period of revolution. There are two types of comets:

• short-period with a period of circulation from two, five years to a couple of hundred years;
• long-period comets, orbiting with a period of two, three hundred years to a million years.

The former include celestial bodies that move fairly quickly in their orbit. Among astronomers, it is customary to designate such comets with the prefixes P/. On average, the period of revolution of short-period comets is less than 200 years. This is the most common type of comet encountered in our near-Earth space and flying in the field of view of our telescopes. Halley's most famous comet takes 76 years to orbit the sun. Other comets visit our solar system much less frequently, and we rarely see them. Their period of revolution is hundreds, thousands and millions of years. Long-period comets are designated in astronomy by the prefix C/.

It is believed that short-period comets have become hostages of the gravity of the major planets of the solar system, which managed to snatch these celestial guests from the strong embrace of deep space in the Kuiper belt region. Long-period comets are larger celestial bodies that come to us from the far corners of the Oort cloud. It is this region of space that is the birthplace of all comets that regularly visit their star. After millions of years, with each subsequent visit to the solar system, the size of long-period comets decreases. As a result, such a comet can become a short-period comet, shortening its cosmic lifetime.

During space observations, all comets known to date have been recorded. The trajectories of these celestial bodies are calculated, the time of their next appearance within the solar system, and approximate sizes are established. One of them even showed us his death.

The fall in July 1994 of the short-period comet Shoemaker-Levy 9 on Jupiter was the brightest event in the history of astronomical observations of near-Earth space. The comet near Jupiter broke into fragments. The largest of them measured more than two kilometers. The fall of the heavenly guest on Jupiter continued for a week, from July 17 to July 22, 1994.

Theoretically, a collision of the Earth with a comet is possible, however, of the number of celestial bodies that we know today, not one of them intersects with the flight path of our planet during its journey. There is still a threat that a long-period comet will appear on the path of our Earth, which is still beyond the reach of detection tools. In such a situation, the collision of the Earth with a comet can turn into a catastrophe on a global scale.

In total, more than 400 short-period comets are known that regularly visit us. A large number of long-period comets come to us from deep, outer space, being born at 20-100 thousand AU. from our star. In the 20th century alone, more than 200 such celestial bodies were recorded. It was almost impossible to observe such distant space objects through a telescope. Thanks to the Hubble telescope, images of the corners of space appeared, in which it was possible to detect the flight of a long-period comet. This distant object looks like a nebula adorned with a tail millions of kilometers long.

The composition of the comet, its structure and main features

The main part of this celestial body is the nucleus of a comet. It is in the nucleus that the main mass of the comet is concentrated, which varies from several hundred thousand tons to a million. By their composition, celestial beauties are ice comets, therefore, upon closer examination, they are dirty ice lumps of large sizes. In its composition, an ice comet is a conglomerate of solid fragments of various sizes, held together by cosmic ice. As a rule, the ice of the nucleus of a comet is water ice with an admixture of ammonia and carbon dioxide. Solid fragments are composed of meteoric matter and can have dimensions comparable to dust particles or, conversely, have dimensions of several kilometers.

In the scientific world, it is generally accepted that comets are cosmic deliverers of water and organic compounds in outer space. Studying the spectrum of the core of the celestial traveler and the gas composition of its tail, the icy nature of these comic objects became clear.

The processes that accompany the flight of a comet in outer space are interesting. For most of their journey, being at a great distance from the star of our solar system, these celestial wanderers are not visible. Highly elongated elliptical orbits contribute to this. As it approaches the Sun, the comet heats up, as a result of which the process of sublimation of cosmic ice, which forms the basis of the comet's nucleus, starts. In plain language, the ice base of the cometary nucleus, bypassing the melting stage, begins to actively evaporate. Instead of dust and ice, under the influence of the solar wind, water molecules are destroyed and form a coma around the comet's nucleus. This is a kind of crown of a celestial traveler, a zone consisting of hydrogen molecules. A coma can be huge, stretching for hundreds of thousands, millions of kilometers.

As the space object approaches the Sun, the speed of the comet rapidly increases, not only centrifugal forces and gravity begin to act. Under the influence of the attraction of the Sun and non-gravitational processes, the evaporating particles of cometary matter form the tail of a comet. The closer the object is to the Sun, the more intense, larger and brighter the tail of the comet, which consists of rarefied plasma. This part of the comet is the most noticeable and is considered by astronomers to be one of the brightest astrophysical phenomena visible from Earth.

Flying close enough to the Earth, the comet allows us to examine in detail its entire structure. Behind the head of a celestial body, a plume necessarily stretches, consisting of dust, gas and meteoric matter, which most often falls on our planet in the future in the form of meteors.

History of Comets Observed from Earth

Various space objects constantly fly near our planet, illuminating the sky with their presence. With their appearance, comets often caused unreasonable fear and horror in people. Ancient oracles and astrologers associated the appearance of a comet with the beginning of dangerous life periods, with the onset of cataclysms on a planetary scale. Despite the fact that the tail of a comet is only a millionth of the mass of a celestial body, it is the brightest part of a cosmic object, giving 0.99% of the light in the visible spectrum.

The first comet to be detected with a telescope was the Great Comet of 1680, better known as Newton's Comet. Thanks to the appearance of this object, the scientist was able to obtain confirmation of his theories regarding Kepler's laws.

During the observation of the celestial sphere, mankind has managed to create a list of the most frequent space guests who regularly visit our solar system. Halley's comet definitely tops this list, a celebrity that has lit up us with its presence for the thirtieth time. This celestial body was observed by Aristotle. The nearest comet got its name thanks to the efforts of the astronomer Halley in 1682, who calculated its orbit and the next appearance in the sky. Our companion with a regularity of 75-76 years flies in our visibility zone. A characteristic feature of our guest is that, despite the bright trace in the night sky, the comet's nucleus has an almost dark surface, resembling an ordinary piece of coal.

In second place in popularity and celebrity is Comet Encke. This celestial body has one of the shortest periods of revolution, which is 3.29 Earth years. Thanks to this guest, we can regularly observe the Taurids meteor shower in the night sky.

Other most famous recent comets, which made us happy with their appearance, also have enormous orbital periods. In 2011, comet Lovejoy was discovered, which managed to fly in close proximity to the Sun and at the same time remain safe and sound. This comet is a long-period comet with an orbital period of 13,500 years. From the moment of its discovery, this celestial guest will stay in the region of the solar system until 2050, after which it will leave the limits of near space for a long 9000 years.

The brightest event of the beginning of the new millennium, literally and figuratively, was Comet McNaught, discovered in 2006. This celestial body could be observed even with the naked eye. The next visit to our solar system by this bright beauty is scheduled in 90 thousand years.

The next comet that may visit our firmament in the near future will probably be 185P/Petru. It will become noticeable starting on January 27, 2018. In the night sky, this luminary will correspond to the brightness of 11 magnitudes.

If you have any questions - leave them in the comments below the article. We or our visitors will be happy to answer them.

General information

Presumably, long-period comets fly to us from the Oort Cloud, which contains millions 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.

More than 400 short-period comets have been discovered so far. Of these, about 200 have been observed in more than one perihelion passage. Many of them are included in the so-called families. For example, approximately 50 of the shortest period comets (their full revolution around the Sun lasts 3-10 years) form the Jupiter family. Slightly smaller than the families of Saturn, Uranus and Neptune (the latter, in particular, includes the famous comet Halley).

Comets emerging from the depths of space look like nebulous objects, behind which a tail stretches, sometimes reaching a length of millions of kilometers. The nucleus of a comet is a body of solid particles and ice, shrouded in a foggy shell called a coma. A nucleus with a diameter of several kilometers can have around it a coma 80,000 km across. Streams of sunlight knock particles of gas out of the coma and throw them back, pulling them into a long smoky tail that drags 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 approaches the Sun and the Earth enough to be seen with the naked eye. The most notable ones are sometimes referred to as the "Great Comets".

The structure of comets

Comets move in elongated elliptical orbits. Notice the two different tails.

As a rule, comets consist of a "head" - a small bright clot-core, which is surrounded by a light foggy shell (coma), consisting of gases and dust. In bright comets, as they approach the Sun, a “tail” is formed - a weak luminous band, which, as a result of light pressure and the action of the solar wind, is most often directed in the opposite direction from our luminary.

The tails of celestial wanderers of comets differ in length and shape. Some comets have them stretching across the sky. For example, the tail of a comet that appeared in 1944 [ specify], was 20 million km long. Comet C/1680 V1 had a tail stretching for 240 million km.

Comet tails do not have sharp outlines and are practically transparent - stars are clearly visible through them - as they are formed from extremely rarefied matter (its density is much less than the density of gas released from a lighter). Its composition is diverse: gas or the smallest dust particles, or a mixture of both. The composition of most of the dust grains is similar to the asteroid material of the solar system, which was revealed as a result of the study of Comet Wild (2) by the Stardust spacecraft. In essence, it is "visible nothing": a person can observe the tails of comets only because the gas and dust glow. At the same time, the glow of the gas is associated with its ionization by ultraviolet rays and streams of particles ejected from the solar surface, and the dust simply scatters sunlight.

The theory of tails and shapes of comets was developed at the end of the 19th century by the Russian astronomer Fyodor Bredikhin (-). He also owns the classification of comet tails, which is used in modern astronomy.

Bredikhin suggested that the tails of comets be classified into three main types: straight and narrow, directed directly from the Sun; wide and slightly curved, deviating from the sun; short, strongly deviated from the central luminary.

Astronomers explain such different forms of comet tails as follows. The particles that make up comets have different compositions and properties and respond differently to solar radiation. Thus, the paths of these particles in space "diverge", and the tails of space travelers take on different shapes.

Comets up close

What are comets themselves? Astronomers got an exhaustive idea of ​​them thanks to the successful "visits" to Halley's comet by the spacecraft "Vega-1" and "Vega-2" and the European "Giotto". Numerous instruments installed on these vehicles transmitted to Earth images of the comet's nucleus and various information about its shell. It turned out that the nucleus of Halley's comet consists mainly of ordinary ice (with small inclusions of carbon dioxide and methane ice), as well as dust particles. It is they that form the shell of the comet, and as it approaches the Sun, some of them - under the pressure of the sun's rays and the solar wind - pass into the tail.

The dimensions of the nucleus of Halley's comet, as scientists correctly calculated, are equal to several kilometers: 14 in length, 7.5 in the transverse direction.

The nucleus of Halley's comet has an irregular shape and rotates around an axis, which, as the German astronomer Friedrich Bessel (-) suggested, is almost perpendicular to the plane of the comet's orbit. The rotation period turned out to be 53 hours - which again agreed well with the calculations of astronomers.

NASA's Deep Impact spacecraft rammed Comet Tempel 1 and transmitted images of its surface.

Comets and Earth

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, the "celestial guests" do not affect the planets of the solar system in any way. In May, the Earth, for example, passed through the tail of Halley's comet, but there were no changes in the motion of our planet.

On the other hand, a collision of a large comet with a planet can cause large-scale consequences in the planet's atmosphere and magnetosphere. 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.

Links

• Collision of comet Shoemaker-Levy 9 with Jupiter: what we saw (Physics of our days)

Since ancient times, people have sought to uncover the secrets that the sky is fraught with. Ever since the first telescope was created, scientists have begun, step by step, to collect 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 of revolution. 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 on a much larger scale 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 reflection on 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.