Tailed comets. Comets are tailed stars. Why does a comet have a tail?

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Comets. Where are they from?

The appearance in the sky of a celestial body with a brightly glowing head and a long tail is an amazing and unforgettable sight. But if modern man knows that this object is one of the celestial bodies called a comet, and when he sees it he experiences only a feeling of delight, then the feelings of ancient man when he saw tailed objects were completely different.

Since comets were considered harbingers of various kinds of misfortunes and misfortunes, people, when they saw them, experienced natural horror.

In addition to the fact that comets are endowed with a unique beauty, they are also the most extensive bodies in the solar system. For example, a comet that appeared in the sky in 1811 has only a head that is six to eight times larger in volume than the Sun. And the comet of 1882 had a tail that reached Jupiter.

Usually a comet consists of three parts: the nucleus, in which the bulk of the comet's mass is concentrated, the head, or "coma", and the tail. The tail, consisting of plasma, gas and smoke, is so rarefied that under terrestrial conditions such a medium is considered a vacuum. And the tail, as well as the head of the comet, is visible only when it approaches the Sun.

Thus, to some approximation, a comet is practically empty space, or visible nothingness. But at the heart of this “clump of vacuum” there is a small, usually several kilometers in diameter, solid core consisting of a mixture of various ices, more than 80% of which is water. The rest of the core is represented by solid carbon dioxide, or “dry ice,” as well as methane and ammonia ice and other frozen gases.

Scientists, in particular astrobiologists, believe that the substance of the core requires detailed study, since this giant “refrigerator” can store ancient organic compounds, that is, those from which life on Earth arose.

Comet ice also contains dust and small rocky substances. And when the comet approaches approximately 4.5 AU. towards the Sun, the temperature of its outer layer rises to -140 °C. This causes the ice to begin to evaporate, leaving a crust of microscopic dust particles on the surface of the core. Moreover, they are so small that they are difficult to see even with a magnifying glass. True, there are also larger particles: for example, grains of sand and pebbles...

During the process of evaporation, substances leave the comet in a certain sequence. First, methane, ammonia, hydrogen and cyanogen evaporate, from which the transparent atmosphere of the comet is formed - its head. Then the carbon dioxide sublimes. And this process is completed by water, which requires higher temperatures for its evaporation.

But not only streams of photons rush from the Sun, but also the solar wind, which is a stream of charged particles that carry with them fragments of the solar magnetic field.

Colliding with the head of a comet, this wind, using magnetic fields like networks, picks up ions of cometary gas and carries them away from the Sun at a speed of 500-1000 kilometers per second. The result is a long and straight plasma tail, like a searchlight beam.

And since the solar wind does not act on neutral gas particles, they remain within the nucleus, filling the head of the comet, which becomes larger and larger...

Some more time passes, and the comet begins to demonstrate a real extravaganza: gas geysers burst out from under its brown crust, and a cold luminescent glow pours from its head. In this case, the cometary gas glows in exactly the same way as rarefied gas in fluorescent lamps.

During gas eruptions, huge plumes of tiny dust particles rise upward. Quanta of sunlight strike these microparticles, carrying them away from the Sun. As a result, a different tail appears - not straight, but curved, which, like a bride’s train, stretches behind her, arching along the orbit.

Thanks to their tails, comets can have different appearances: some have a tail made of ions, others have a tail made of dust; some even have two tails and almost real “beards”.

When a comet flies into Earth's orbit, it enters an area of ​​relatively high temperatures and begins to heat up greatly. For this reason, geysers of gas and dust are now flowing in continuous streams. During this period, the core loses 30-40 tons of steam every second. At the same time, subcortical emissions occur, reminiscent of explosions of depth charges.

The closer the comet is to the Sun, the more intensely the ice evaporates from it. And the escaping gas forms a luminous sphere, or coma, around the core, the diameter of which can reach a million kilometers.

All these processes have raised many questions for astronomers that still remain unanswered: for example, what makes a volume of ice the height of an 8-10-story building suddenly evaporate from the depths of a comet, or what forces eject a huge amount of gas over 20-30 thousand kilometers?

Astronomers have no doubt that comets arrive in the solar system from somewhere far away. But they cannot say exactly where exactly, although they have been looking for an answer to this question for a long time.

To date, several hypotheses for the origin of comets have been proposed. And they all have their pros and cons.

The oldest of the hypotheses was put forward in the Middle Ages. Then astronomers assumed that comets appear during volcanic eruptions on Jupiter and Saturn. By the way, the idea of ​​​​medieval scientists about the volcanic nature of comets, although in a slightly modified form, has survived to this day. Moreover, many modern astronomers believe that comet nuclei are ejected not only by the giant planets themselves, but also by their satellites. And proof of this point of view can be the fact of the discovery of volcanic activity on the satellite Io, closest to Jupiter.

Adherents of another hypothesis adhere to the point of view that comets arrive into the Solar system from its periphery, where at a distance of 50-150 thousand AU. there is a huge accumulation of these “tailed” objects.

After the Dutch astronomer J. Oort, this region was called the Oort cloud. It is assumed that from this region, under the influence of the gravity of stars located close to the solar system, comets slowly move towards the Sun. But over time, the speed of their movement gradually increases, and after millions of years they accelerate so much that they rush into the vicinity of our star like a whirlwind, go around it and fly away again.

However, sometimes it happens that, flying close to one of the large planets, they are exposed to its gravitational influence, change their flight path and, heading deep into the solar system, become its permanent inhabitants, or periodic comets.

According to the third hypothesis, comets are of interstellar origin. It is possible that the Oort cloud, which appeared after the formation of the Solar System, periodically delivers comets into the interstellar medium to this day. And from here they are “captured” by large planets: for example, Jupiter or Saturn.

But this hypothesis also has a number of weak points. Thus, it is not able to explain the frequent appearance of comets in the solar system.

Thus, none of the above hypotheses found full support among astronomers, since they could not explain many features of the structure, composition and movement of comets. That is why the question of their origin remains open to this day.

As an addition, apparently, one exotic hypothesis should be mentioned. The few scientists who support it believe that individual comets are reconnaissance ships of alien civilizations that have been collecting information about the solar system and, in particular, about the Earth for more than 1000 years.

And some of the available data do not even seem to contradict this idea. For example, the movement of a number of comets cannot be explained by the attraction of known objects of the solar system: in particular, some comets demonstrate secular accelerations of movement, while others, on the contrary, slow down. Hence the question: how can a lifeless body in airless space change its speed? Moreover, every time the comet is close to the Sun, a significant part of its matter is spent on the formation of its tail. But, having disappeared from the sky, after some time it returns again. What is the reason for this consistency? Where is the law of conservation of matter? Obviously, somewhere in the cosmic abyss, comets are undergoing changes unknown and incomprehensible to us today...

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Since ancient times, people have watched the starry sky with admiration and surprise, trying to understand its secrets. Throughout human history, astronomers, step by step, bit by bit, have collected information about space, including very interesting space objects - comets, which our article is about today.

What is a comet

The word “comet” itself is of ancient Greek origin, and our language translates as “with long hair.” Of course, this name is not accidental, because a mandatory attribute of any decent comet is the presence of a long tail, which the poetic ancient Greeks thought of as “hair.”

So, a comet is a small celestial object moving around the Sun in a highly elongated orbit, having a “head” and a “tail.” At first, astronomers considered comets to be travelers from outside ours who were “passing through” here, but later they found out that comets never leave the solar system, that is, they are not “tourists” here, but “permanent residents.”

Comets are also very often confused with other flying celestial objects: asteroids and meteorites, but we will try to clarify at this point and formulate the difference between them.

How are asteroids different from comets?

In general, comets and asteroids have many common features: they revolve around the Sun, have unusual orbits, and comets and asteroids can fly, including close to the Earth, as well as other planets in the Solar System. But what is their difference? In fact, a comet differs from an asteroid in many ways:

• By composition: asteroids consist of rocky material and, comets are formed of ice, dust, rocks and organic compounds. Due to the presence of ice in its composition, it is dangerous for comets to fly close to the Sun; the ice begins to melt, and comets lose a significant part of their volume. Asteroids can fly close to the Sun without any consequences.
• By the presence of a tail: comets have tails, asteroids, as a rule, do not. Although not so long ago, astronomers noticed asteroids (for example, an asteroid code-named P/2010 A2) that also had tails, but the nature of the formation of tails in asteroids is different than in comets. An asteroid's tail is formed due to its impact with other asteroids, which causes a large emission of dust and gas from its surface, creating the “tail effect.” But in general, an asteroid’s tail is the exception rather than the rule. We will talk about the nature of the comet's tail below.
• By orbit: asteroids have shorter and more circular orbits, while comets have wider and longer orbits.

What is the difference between a meteorite and a comet?

The meteorite is also very similar to a comet, but there are many differences between them:

• Size: meteorites are several times smaller than comets; if a comet can have a diameter of several kilometers, then meteorites can boast only a few meters.
• Meteorites, like most asteroids, do not have a tail, this decoration of all comets. In general, the shape of a meteorite is different from that of a comet.
• The composition of a comet and a meteorite is also different, as we wrote above, a comet consists of ice, dust, rocks and organic compounds, while a meteorite is created from some solid substance (rock, metal, ore).
• And the main difference is in the essence of a meteorite, because in essence it is an object that represents the process of the fall of a celestial body, while a comet is a full-fledged “inhabitant of outer space”, unlike a meteorite, it does not fall anywhere (although there are exceptions), but simply flies around within the solar system.

Comets and history

In ancient times, comets were the cause of numerous superstitions, and even miracles. Often their appearance in the night sky was associated, either with omens of various misfortunes, or, on the contrary, with great beneficial events. Thus, the famous “Star of Bethlehem”, described in the Bible, which, according to the Gospel of Matthew, the wise men saw in the starry sky and realized that the “King of the Jews” was born, was most likely just a comet.

Prominent scientists of antiquity also wrote about comets in their works, in particular, Aristotle believed that comets are luminous gas, and the Roman philosopher Seneca suggested that comets are celestial bodies that move in their orbits.

The famous Halley's comet made a lot of noise in history, which was seen more than once in the starry sky and its appearance was always associated with various historical events. For example, it is believed that the arrival of Halley's comet in 1066 brought with it the death of the English king Harold II and the victory of William the Conqueror - one of the turning points in the history of the European Middle Ages.

The appearance of Halley's Comet in 1066, a fragment of the Bayeux Tapestry glorifying the victory of William the Conqueror.

What are comets made of?

Today, science has made significant progress in the study of these interesting celestial objects, including determining their composition. So, comets consist of a solid core, which in turn consists of frozen water and cosmic dust. The comet itself, as we wrote above, consists of ice, dust, rock and organic compounds.

How a comet's tail is formed

Where does a comet's tail come from, in general, what causes the formation of comet tails? The characteristic fiery tail of a comet is an emission of gas and dust occurring under the influence of solar energy. As a comet flies closer to the Sun, its surface heats up, leading to this ejection, which creates the comet's tail. Moreover, if asteroids have tails only when they collide with something, a comet will have tails simply when it flies a little closer to the Sun due to the structural features of the comet itself. It is also interesting that the comet's tail is always directed away from the Sun.

Age of comets

Nothing lasts forever under the Moon, even stars have their age, and comets even more so. Moreover, comets have a peculiar life cycle; at first they are young and then grow old. Aging in comets is manifested in the fact that while flying around the Sun, they gradually lose their volume, which is from the comet under the influence of solar energy (the tail of the comet is precisely the product of this evaporation).

Comet crash

The fall of a comet on any planet (including our Earth) is an unlikely event, but the key word here is “probable”, that is, as a result of a certain set of circumstances, the comet may fall (or rather even crash) into one or another planet. As you probably guessed, this does not bode well for the planet, since as a result of the fall of the comet, a huge explosion will follow, comparable in power to the explosions of hundreds of thousands of atomic bombs.

• There is also a mention of a comet as a bad omen in our history, namely the Tale of Bygone Years, which astronomers at that time considered to be “moving tailed stars.”
• Some scientists believe that the famous Comet Halley, which appears in our starry sky every 75 years, could well be the no less famous “Star of Bethlehem” from the Bible.

Comets, video

And in conclusion, an interesting documentary about the most legendary comets living in our solar system.

Among other “extraordinary” celestial phenomena that we have not yet talked about, comets have attracted and continue to attract human attention (the word comet comes from the Greek word “cometes”, which means “tailed”, “hairy”). Large comets - bright celestial bodies with a long luminous tail - are a rare, memorable sight.

The suddenness of the appearance of such comets, their unusual appearance and increasing size have caused fear in people since ancient times. Churchmen and all kinds of “foretellers” associated various disasters with the appearance of comets - crop failures, diseases, wars, the death of the Earth. Comets were considered a manifestation of God’s wrath, an ominous celestial sign.”

Most medieval scientists also had an ignorant view of comets. Thus, back in the 17th century, the German Hildebrandt divided comets into eight groups according to their “malicious actions.” He included comets that cause illness in the first group, and comets that portend hard times and famine in the second group, etc.

Almost everyone was sure that comets could spread harmful fumes into the air that affected people.

Thanks to this look at these, in fact, they are completely safe for the Earth and its inhabitants.

Cosmic bodies, every appearance of comets was described in detail by historians.

Here is how, for example, a comet that appeared in 1066 is described in the Russian chronicle:

“At these times there was a sign in the west, a great star, with a ray like a bloody one, rising in the evening after sunset and remaining for seven days; These manifestations are not for good: therefore, there was a lot of strife and the invasion of the filthy on the Russian land, and therefore the star was like bloody, showing bloodshed.”

Apparently, the tail of the comet of 1066 was visible against the background of the evening dawn and therefore appeared “bloody,” that is, red.

The medieval view of comets as something terrible persisted until the very recent past. More recently, many superstitious conversations and rumors were associated with the appearance of a bright comet with the question: what will happen if the comet collides with the Earth?

In May 1910, when the bright Comet Halley appeared in the sky, the newspapers reported: “Viennese astronomers are convinced that the comet’s tail will touch the Earth. There is panic among the population, especially in the provinces.” Many residents of Tehran (Iran) dug holes and hid in them from “heavenly wrath.”

Many ridiculous rumors about Halley's Comet of 1910 spread in Tsarist Russia. The population, not knowing the true reasons for this completely natural natural phenomenon, believed any nonsense fiction. Taking advantage of this, the churchmen frightened people with the “end of the world” and “God’s punishment” for their sins. Prayer services were held on the streets of the cities. At the same time, the authorities prohibited scientific conversations about comets. Thus, in Moscow, a popular lecture on Halley’s Comet by astronomer K-L was banned. Baeva in the work circle “Knowledge of the Sky”.

Currently, the nature of comets is well studied. The comet appears in the sky as a small, inconspicuous, foggy speck. But several days pass, and in the night sky you can already see a bright star, as if shrouded in a light cloud. The "star" is growing rapidly. With great speed it rushes towards the Sun. A few more days pass, and the comet takes on a new unusual appearance: a long luminous tail, reminiscent of fiery hair, appears behind it! Its brightness is increasing, the comet is already visible during the day, in the sun.

Having circled the Sun, the bright “tailed star” begins to move away from it. As it moves away from the Sun, the brightness of the comet decreases, its tail gradually disappears, and after a short time the comet again becomes an inconspicuous nebulous speck.

The appearance of such a bright comet, clearly visible to the naked eye, is a rare phenomenon. Over the past century, large comets of 1843, 1858 and 1910 have been known, for example. Most recently, a bright comet was observed in the southern hemisphere in December 1947.

But the total number of comets in global space is enormous. Most of them are invisible to the naked eye, but with the help of telescopes they can often be seen. Astronomers usually observe several comets every year.

Science has established that, like planets, comets move around the Sun under the influence of its gravity, approaching it at certain intervals.

Comet Halley, which we have already mentioned, which was last observed near the Sun in 1910, completes its complete revolution around the Sun in 75-77 years (Fig. 22). Before 1910 she visited close

Sun in 1835, 1759 and earlier. A total of 28 cases of its occurrence were noted. The appearance of Halley's comet was noted in Chinese chronicles, 240 years BC.

The next appearance of Halley's Comet should be expected around 1986.

The orbital time of comets around the Sun varies. Thus, the small comet Encke orbits the Sun in just over three years. On the other hand, there are also known comets whose period of complete revolution around the Sun is more than one thousand years.

The paths of movement of many comets have now been studied so well that scientists know in advance where and when this or that “tailed star” will be visible in the sky.

By studying comets, astronomers have found that the mass of comets is negligible; for the largest comets it is many millions of times less than the mass of the Earth. Observations show that comets are not a solid solid body: stars shine through the foggy body of the comet. On the other hand, it has been established that the accumulation of gases and fine dust cannot exist for long. A stable accumulation of small particles of matter, such as comets, should consist of fairly large fragments - from 1 centimeter or more.

Observations of passing comets made it possible to establish that comets contain fragments hundreds of meters in size.

Typically, a comet's head, nucleus, and tail are distinguished. The nucleus of a comet's head is the brightest part of the head; it consists of small fragments and stones. The core is shrouded in a shell of dust and gases.

When a comet approaches the Sun, its core heats up and begins to release gases: nitrogen, carbon monoxide (carbon monoxide) and others - they form a foggy shell and one or more tails of the comet.

The tails of comets point away from the Sun. This occurs due to the fact that the hot gases and tiny particles that make up the comet's tail are under pressure from the sun's rays. The pressure of light on solids and gases was proven by the famous Russian physicist P. N. Lebedev.

The works of the greatest Russian scientist F.A. Bredikhin and the Soviet scientist S.V. Orlov, who was awarded the Stalin Prize, were of great importance in the study of comets and comet tails. Prof. S.V. Orlov showed that the size of cometary nuclei cannot exceed 10 kilometers in diameter. From this it is clear that even a direct collision of a comet with the Earth does not threaten our planet with any kind of catastrophe, about which so much was written quite recently in science fiction stories. The earth has a fairly strong armor - an air shell. And the mass of comets itself, in comparison with the mass of the Earth, as we have already said, is insignificant.

And such direct collisions of the Earth with comets have already happened more than once. In 1872, for example, the Earth collided with the remnants of Comet Biela, which disintegrated in 1846. The result of this collision was only an abundant “star rain” (the “star rains” are discussed further). It was the smallest fragments and dust particles flying through our atmosphere that entered the comet's nucleus. Most of them did not reach Earth.

A collision with comet tails does not promise anything terrible for the Earth. Such cases have also happened many times. So, in May 1910, the Earth, as astronomers expected, actually passed through the tail of Comet Halley and this did not harm us in any way. The air envelope of the Earth reliably protects us from the penetration of meteoric dust and gases.

What does the Milky Way look like?

The most mysterious and beautiful thing in the sky, apparently, is the Milky Way, stretching like a necklace of precious stones from one end of the sky to the other. In ancient times, people, looking at this picture, like us, were surprised and delighted by this beauty. Not knowing what it could be, they gave unusual and sometimes beautiful explanations for the Milky Way.

For example, at the birth of Christianity, people believed that this was the road of angels along which they could ascend to heaven. They also thought that this was a hole in the sky that allowed those living on Earth to see what was beyond the firmament.

Our current knowledge of the Milky Way does not prevent us from admiring it. The reality is as amazing as the ancient legends about its supposed creation.

Our galaxy, round and flat, is shaped like a clock. If we could look at it from above, we would see that the galaxy really does look like a clock. But we are inside the galaxy, and when we look up, it is as if we are looking at the edge of a clock from the inside. We watch their edge curve around us. These millions of stars make up the Milky Way.

Did you know that the galaxy consists of 3 billion stars? And we have an idea of ​​its size. Light from the Sun reaches the Earth in 8 minutes, and a ray of light will travel the distance from the center of the galaxy to the Sun in 27,000 years.

The galaxy rotates around its axis like a wheel. A complete revolution takes 200 million years.

What is the Southern Cross?

To the south of the equator, four stars are visible in the sky, forming a cross-like figure. This is the so-called Southern Cross. It gives directions and helps travelers find their way at night.

As we have already said, the Southern Cross refers to the constellations that are visible only in the Southern Hemisphere. The constellation Ursa Minor plays approximately the same role in the Northern Hemisphere. Indeed, both are located on the north-south axis of the globe and are almost motionless. Therefore, they always show only one direction: the North Star in Ursa Minor is north, and the Southern Cross Quartet is south.

What is star shower?

Have you ever observed so-called “shooting stars” in the night sky - single luminous points sweeping across the sky? There is even a belief: if you see a “shooting star” and make a wish, it will definitely come true. Meanwhile, these are not “stars” at all, but meteors - flashes and glows that are caused by the invasion of tiny solid cosmic particles into the Earth’s atmosphere. Every year there are nights when dozens, hundreds of meteors flash in the sky. This is star or meteor shower.

Particles moving in interplanetary space, formed due to the gradual disintegration of comets, sometimes fall into the upper layers of the Earth's atmosphere and, before reaching the surface of the planet, burn up. This is due to the enormous speeds of movement of meteoroids (by the way, they weigh no more than a gram) and the relatively high density of air. The particles instantly heat up to several thousand degrees and evaporate. The result – luminous gas – is what we see in the night sky. Meteor showers are the result of our planet encountering a swarm of meteor particles or a meteor shower. “Falling stars” appear one after another, as if from one point in the sky (it is called the radiant) and scatter in all directions. In fact, all the particles of the meteor shower move parallel to each other and seem to fly apart only in perspective.

A real shower of stars, when thousands (!) of meteors can be registered in an hour, is a rare phenomenon in our country. And it happens in cases where the Earth crosses the orbits of large comets. Such as the famous Comet Halley or Comet Giacobini-Zinner (named after the two astronomers who first discovered it). It is clear that you cannot see so many meteors with your eye. Therefore, since the 30s, “shooting stars” have been photographed. A system of cameras covering the entire starry sky and designed to record meteors is called a meteor patrol. However, it does not always help, since it is not able to “catch” dim particles. Since the 1940s, astronomers have also used radars.

What is a planet?

Nine celestial bodies revolve around our Sun. These are planets. In turn, small celestial bodies - satellites - revolve around the planets. So, the Earth is a planet, and the Moon is its satellite.

A planet is a celestial body that does not have its own radiation. It glows only with the reflected light of the Sun. There are nine planets in our solar system. Mercury and Venus are closer to the Sun than the Earth. Pluto is the most distant planet. There is also Mars, Jupiter, surrounded by the rings of Saturn, Uranus and Neptune. The Earth has only natural satellite - the Moon. But Jupiter has sixteen of them. Venus is called the Morning Star: it is located close to the Sun and appears in the sky immediately after sunset or early in the morning, at dawn.

What is a comet?

A comet is the same celestial body as the Earth or the Moon, only small in size (up to 20 kilometers in the core). Comets move around the Sun in highly elongated orbits. When we see a comet, it looks like a bright point with a long sparkling tail. In all centuries, the appearance of “tailed monsters” has caused fear among people. People considered them harbingers of disasters and wars.

Scientists believe that comets are balls of frozen water and gas mixed with dust and rock particles.

The light source is the “head”, or nucleus, of the comet. As it approaches the Sun, a comet develops a tail. It consists of very rarefied gas and tiny particles that fall off the comet's nucleus under the influence of the Sun. The comet's nucleus is surrounded by a third part called the "envelope". This is a luminous cloud of solid matter that can reach a diameter of 250,000 kilometers or more.

The tails of comets vary in shape and size. Some are short and wide, others are long and thin. Usually their length reaches about 10 million kilometers, and sometimes – 180 million kilometers. And some comets have no tail at all.

As the tail grows, the speed of the comet increases as it approaches the Sun. At this time, the comet moves head first. And then something strange happens. A comet, moving away from the Sun, moves tail first. This occurs because the rays of the Sun tear off the smallest particles of matter from the comet's nucleus, forming the comet's tail, in the direction opposite to the Sun.

Therefore, as a comet moves away from the Sun, it moves tail first. At this time, the speed of the comet's movement decreases, and we gradually lose sight of it. Comets can disappear for many years, but most gradually return. Every 76 years a large comet appears near the Earth. It's called Halley's Comet. Halley was first depicted in a Chinese drawing in 168 BC. e. In 1682, Edmund Halley, the British Astronomer Royal, observed the movement of this comet, and after carefully checking his records, he decided that this particular comet appeared every 76 years. In 1986, a spacecraft was launched to collect data on Halley's Comet. He transmitted 2,000 photographs to Earth showing the shape and size of the comet. It turned out that Halley's comet is 2 times larger than scientists thought. Its length is over 16 kilometers and its width is almost 10 kilometers.

Currently, astronomers have recorded almost 1,000 comets, but there may be several hundred thousand comets in our solar system that are invisible to us.

Why does a comet have a tail?

If you look at a comet through a telescope, you will notice that it has a “head” and a “tail.” The "head" is a large cloud of glowing gas called the comet's epicenter. The epicenter can reach more than 1,609,300 kilometers in diameter. These gases are so light that the solar winds blow them back. Thus, a “tail” is formed.

As a comet approaches the Sun, its tail becomes larger and larger because the pressure from the solar winds increases. As the comet moves away from the Sun into the cold Universe, the pressure of the solar winds decreases, but they still continue to blow out the gases of the comet. For this reason, the comet's "tail" is always directed away from the Sun.

A small, shining point of light can sometimes be seen at the epicenter of a comet. This point of light is called the comet's nucleus. Astronomers believe that the core is a mixture of ice and dust particles that form a ball up to 50 kilometers in diameter.

As they orbit the Sun, most comets move in elongated orbits. They are shaped like a long, thick cigar. It takes a comet thousands of years to complete one circle in its orbit.

Three or four times a century, a comet passes so close to the Sun that its bright, shining “tail” is easily visible from Earth. We can only observe a comet when it passes close to the Sun. The Sun then turns the ice of the comet's nucleus into gas. Radiation emanating from the Sun passes through the gases and ionizes them, causing the gases to glow.

Can a comet explode?

In previous centuries, people believed that comets foreshadowed terrible disasters, epidemics of terrible diseases, wars, earthquakes and the like. Now this superstitious fear is a thing of the past, but many still think that comets can cause great harm to the Earth. For example, what will happen if some comet currently located near our planet explodes?

As far as we know, comets don't explode. However, sometimes they fall apart. For example, one comet, the appearance of which was observed several times, in 1846 broke up into two. Eventually, each of them crumbled into small fragments, forming a meteor shower that can be regularly observed in the last days of November. Thus, sooner or later, each comet dies, collapsing into small parts, which then scatter along its orbit in the form of meteoric dust.

A comet, contrary to widespread misconception, is by no means one huge block rushing at terrible speed through outer space. According to scientists, it is a gigantic stream of solid particles and gases held near them by the force of attraction.

The brightest part of a comet is its head. The center of the comet's head consists of the heaviest particles and is called the nucleus. A part of the comet called the envelope is concentrated around the nucleus. It is a nebulous, cloud-like formation 250,000 kilometers or more in diameter. Behind the comet stretches a tail consisting of rarefied gases and very small particles.

Why do comets disappear?

In addition to planets and their satellites, the Solar System also includes comets. Comets move along specific paths, called orbits, around the Sun at specific speeds. The orbits of many comets are highly elongated and resemble the shape of an elongated thick cigar. Comets orbit past nearby stars. It takes thousands of years for a comet to complete its entire orbit. Therefore, they seem to disappear, but in fact they simply move out of sight.

Comets are greatly affected by the gravitational forces of the planets. Some comets leave their orbits under the influence of these forces, their orbit becomes shorter. Jupiter, for example, has collected a large number of comets, each of which orbits the Sun with an orbital period of 6 years. Comets that appear with a certain regularity are called periodic comets.

Do comets disappear forever? Some disappear. In 1826, astronomer Wilhelm von Biela discovered one of these “vanished comets.” It appeared several times, and each time it was observed by hundreds of astronomers. Then in 1846 the comet split in two, creating two comets. Then both of these parts of Comet Beale broke up into a large number of small ones.

It is believed that these fragments formed the meteor shower that appears in the sky at the end of November. The history of Comet Beale shows that some comets do die; they disintegrate, leave their orbits and become meteorite dust.

What is an asteroid?

Discoveries in the world of celestial bodies often resemble the discovery of a mystery. This is how asteroids were discovered.

Scientists Titius and Bode at different times came to the conclusion that there must be some kind of planet between Mars and Jupiter: there was some kind of gap in the distance between them. Therefore, several astronomers began searching for this planet.

In 1801, a planet was actually discovered at this site, which was named Ceres. But it was a very small planet with a diameter of only 600 miles. Scientists decided that it could be just one of a group of small planets, and the search continued.

After some time, three more planets were discovered, the largest of which was half the size of Ceres. Astronomers decided that these planets were four fragments left after the explosion of some large planet. But after fifteen years of searching, one astronomer found another small planet, and the hunt continued.

By 1890, 300 minor planets had been discovered, and between 1890 and 1927, 2,000 planets! These small planets, mostly orbiting in the space between Mars and Jupiter around the Sun, are called asteroids.

There are an estimated 100,000 of them, although many are too small to be easily detected. Some are only a few hundred meters across, and their total mass is only a small fraction of the Earth's mass.

Regarding the appearance of asteroids, there is a hypothesis according to which they are fragments of an exploded satellite of Jupiter.

What are meteors made of?

Perhaps you have seen a picture where one of the stars suddenly fell from the sky and rushed to the ground. For a long time, these shooting stars remained a mystery to people. In fact, these objects have nothing to do with real stars and are meteors.

Today they have already been quite well studied by astronomers, who believe that meteors are fragments of comets. When comets are broken into millions of small and large pieces, the latter continue to move in the form of “swarms”, or meteor showers. These meteor showers or individual particularly large meteors move through space in constant orbits.

Most meteors are small, but some can weigh several tons. Passing through the earth's atmosphere, they usually burn up completely, and only the largest manage to reach the earth's surface.

A meteor that falls to earth is called a meteorite. The largest of them, weighing 60–70 tons, was found in Africa and still lies at the site of its fall.

Among meteorites, two main types can be distinguished. Those belonging to the first consist mainly of iron and nickel. They are called metal meteorites. Others contain mainly various minerals and look like stone blocks burned by fire. Such meteorites are called stone meteorites, or aeromets. As a rule, both types of meteorites have a black crust on the outside - the result of the strong heating they experienced as they passed through the atmosphere.

How do objects move in space?

Gravity is the force that attracts one object to another in the Universe. This is the force that causes space objects to move towards the Earth.

It was not until the time of Galileo Galilei (1564–1642) that attempts were made to determine the magnitude of gravity. Until this time, it was believed that the speed at which a falling object hits the Earth's surface depended only on the weight of that object.

Galileo threw objects of various weights from a leaning tower in the Italian city of Pisa in order to study the effect of the “force” of gravity on them. He proved that heavy and light objects thrown down together reach the surface of the Earth at the same time.

He made the ball roll down the slope, measuring its position at certain periods of time. Galileo discovered that the increase in speed of a ball is proportional to its time of motion. This means that at the end of the second second he was moving 2 times faster than at the end of the first, at the end of the third - 3 times faster, and so on.

He also calculated that the distance traveled by the ball is proportional to the square of the time of its movement (the square of the number is obtained by multiplying this number by the same value), that is, by the end of the second second the ball had covered a distance 4 times greater than at the end of the first second, at the end of the third - 9 times more, and so on.

Isaac Newton continued his discoveries in the field of gravity. He proposed that the force that attracts an object to the Earth decreases as the distance between the Earth and the object increases. As a result of experiments and observations, Newton derived the law of universal gravitation. The basic principle of the law is that if the mass (amount of matter) of one of the attracted objects doubles, the force of gravity also doubles, but if the distance between the objects doubles, the force of attraction will be 1/4 of its original value.

Albert Einstein tried to answer the question: “What is gravity?” by proving that space-time has four dimensions. This is a very complex theory that requires deep scientific knowledge to understand. According to his latest theory, the gravitational field is connected by electric, magnetic and electromagnetic fields. However, it should be noted that to date no one has yet proposed a definition of gravity that would satisfy everyone.

However, we know that the increase in speed caused by gravity is 10 meters for each subsequent second. This means that the speed of a falling object increases by 10 m/s every second. At the end of the first second the falling speed is 10 m/s, at the end of the second it is 20 m/s, and so on. If at the end of the first second the falling object flies 5 meters, then at the end of the second - 20 meters, at the end of the third - 45 meters.

Why is gravity in space not the same as on Earth?

Every object in the Universe affects another object, they attract each other. This is called gravity, or gravitation. The force of attraction, or gravity, depends on two factors.

Firstly, it depends on how much substance the object, body, item contains. The greater the mass of a body's substance, the stronger the gravity. If a body has very little mass, its gravity is low. For example, the mass of the Earth is many times greater than the mass of the Moon, so the Earth has a greater gravity than the Moon.

Secondly, gravity depends on the distance between bodies. The closer the bodies are to each other, the greater the force of attraction. The farther they are from each other, the less gravity there is.

The Earth has more mass than a person, so gravity keeps him on the Earth. But the Earth acts as if all its matter, all its substance were in the center. Therefore, the force of gravity anywhere on the Earth must be calculated taking into account the distance to its center.

The force of gravity on the sea coast is greater than on the top of the mountain. Now imagine a person who has moved far away from the surface of the Earth. There the force of gravity will be much weaker.

When a person is in space, he completely disappears from the field of gravity. The Earth's gravity has no effect on him at all. He is in a state of weightlessness. Therefore, rockets, spaceships, and astronauts can fly freely in open space.

Do other planets move the same way as Earth?

The Earth has two types of motion. It moves around the Sun along a fixed path called an orbit. The time it takes the Earth to complete this orbit is called a year. The earth also rotates around its axis. The time required for this is called a day. The direction of the axis changes very slowly. This movement is called precession. Other planets also revolve around the Sun and on their own axis, but their rotation speed is different from the Earth's.

The Earth revolves around the Sun at an average distance of 150,000,000 kilometers from it. It takes the Earth more than 365 days to complete its orbit. It takes a little less than 24 hours to rotate around its axis.

Now let's take a look at other planets. Mercury's average distance from the Sun is 58,000,000 kilometers and it takes 88 Earth days to orbit the Sun. It is believed that Mercury rotates around its axis in 58–59 days.

Venus is located at a distance of 108,000,000 kilometers from the Sun. It takes 225 days to make one revolution around it. Venus takes 243 days to rotate on its axis, and it also rotates in a completely different direction. In other words, Venus is a planet rotating from East to West.

Mars, located 228,000,000 kilometers from the Sun, takes 687 days to complete its orbit, and it rotates around its own axis at approximately the same speed as the Earth. Jupiter is 789,000,000 kilometers from the Sun and takes 11.9 years to orbit the Sun, but rotates on its axis in less than 10 hours. Saturn, located at a distance of 1,426,000,000 kilometers from the Sun, takes 29.5 Earth years to complete its orbit. But it only takes 10 hours for it to turn around its axis.

Uranus is located 2,870,000,000 kilometers from the Sun and orbits it every 84 years. Neptune is 4,493,000,000 kilometers away from the Sun. It takes 165 Earth years to complete its orbit.

What is a vacuum?

Most people believe that a vacuum is a space in which there is absolutely nothing.

However, according to scientists, this is simply impossible. They believe that there is no place where there would be no matter at all: not a single molecule of gas or particle of dust. Thus, a vacuum is actually a space where there is very little matter. A deep vacuum means its almost complete absence. However, the main role in this phrase is played by the word “almost”.

One of the simplest ways to obtain a vacuum is to pump out air from the vessel in which it is created.

Currently, there are quite powerful pumps capable of creating very deep vacuums, necessary for both scientific and various industrial purposes. Such pumps, for example, create a vacuum in light bulbs during their production. If the oxygen contained in the air remained in the light bulb, then when it was turned on, the filament would burn out in a split second.

In the most modern light bulbs, it is possible to pump out almost all the air using vacuum pumps. The same can be said about vacuum tubes in televisions or radios, in which as much air as possible is pumped out before sealing.

Another familiar item that uses a vacuum is a regular thermos. It has double walls; a vacuum is created in between them. Since the number of gas molecules in this space is small, they are located at a large distance from each other, and thus the transfer of heat between them is reduced. Therefore, if you pour cold milk into a thermos on a hot summer day, it will remain cold. Conversely, hot tea will not cool down in a thermos, even in the coldest weather.

What is the speed of light?

Light travels at a gigantic speed of 300,000 km/s. When you press a button on an electrical switch, the light appears to come on instantly. And it is true. But it still takes some period of time, albeit very short, for the light of the bulb to reach your eyes.

If the Earth rotated around its axis at the speed of light, it would make 7 revolutions per second. But light, that is, light rays, of course cannot rotate. The rays travel only in a straight line. Light from the Sun reaches us in 8 minutes, covering 150 million kilometers during this time.

What is the speed of sound?

If we hear any sound, then there must be a vibrating object nearby. But this is not enough. Sound has to travel somewhere. Something must carry it from the source to the receiver. This is something called "environment". The medium can be anything - air, water, objects, even earth. The Indians put their ears to the ground to hear distant sounds.

No environment - no sound. If a vacuum is created in some volume, sound will not be able to propagate in it. This is due to the fact that sound travels in waves. A vibrating object transmits its vibration to neighboring molecules or particles. Motion is transferred from one particle to another, which leads to the appearance of a sound wave.

The medium for propagation of sound waves can be various materials - wood, air, water; therefore, the speed of propagation of sound waves must be different. If we talk about the speed of sound, we must ask: in what medium?

The speed of sound in air is 335 m/s. But this is at a temperature of 0 °C. As temperature increases, the speed of sound also increases.

Sound travels faster in water than in air. At a temperature of 8 °C, its propagation speed is about 1,435 m/s, or about 6,000 km/h. In metal, this speed reaches about 5,000 m/s, or 20,000 km/h.

You might think that a strong sound has a higher speed than a weak sound, but this is not true. Its speed does not depend on its height (high or low).

You can conduct an experiment yourself comparing the speed of sound in different environments. Go into the water and hit two stones against each other. Now go under the water and tap those stones again. You will be surprised that sound travels better in water than in air.

What is the sound barrier?

When we say “sound barrier,” we imagine that when an airplane reaches the speed of sound, something like a “barrier” appears. However, nothing like that happens!

To understand all this, consider an airplane flying at a low, normal speed. When an airplane moves in front of it, a compression wave is formed from compressed air particles.

This wave moves ahead of the aircraft at the speed of sound. And its speed is higher than the speed of an airplane, which, as we have already said, flies at low speed. Moving ahead of the plane, this wave forces air currents to flow around the plane of the plane.

Now imagine that the plane is flying at the speed of sound. No compression waves are formed ahead of the plane, since both the plane and the waves have the same speed. Therefore, the wave forms in front of the wings.

As a result, a shock wave appears, which creates large loads on the aircraft's wings. Before airplanes reached and exceeded the sound barrier, it was believed that such shock waves and g-forces would create something like a barrier for the airplane—the “sound barrier.” However, there was no sound barrier, as aviation engineers developed a special design for the aircraft.

By the way, the strong “blow” that we hear when an airplane passes the “sound barrier” is the shock wave that we have already talked about - when the speed of the airplane and the compression wave are equal.

What is a perfect black body?

In physics, an absolute black body is an object that, at any temperature, completely absorbs electromagnetic radiation incident on it. Real physical objects are not absolutely black, but some of them, such as soot, platinum black, black velvet and others, in the region of visible light radiation exhibit properties very close to the properties of an absolutely black body. For example, a surface coated with pure carbon absorbs approximately 97% of the light incident on it.

Some objects exhibit blackbody properties in certain wavelength ranges of electromagnetic radiation and temperatures. Thus, a red filter at room temperature almost completely absorbs green light.

Despite the fact that the concept of a “black body” is purely abstract, it plays an important role in physics in describing the processes of absorption and emission of electromagnetic waves by real objects.

What is a satellite?

In astronomy, a satellite is a body that revolves around a larger body and is held by the force of its gravity. The Moon is the Earth's satellite. The Earth is a satellite of the Sun.

When we use the word satellite, we usually mean a man-made spacecraft orbiting the Earth. Artificial satellites are sent into space for various purposes. Some are used for scientific research, others collect information for weather forecasting.

Some satellites have television and radio antennas. Satellites can be used in navigation and cartography. Man-made satellites give scientists insight into the state of living organisms in space.

Satellites can be of any size, from a small container with tools to a huge cylinder reaching 30 meters in diameter. They can weigh from a few kilograms to many tons. Their shape can be very diverse: round, like a ball, hat-shaped, resembling a tin box, a bell, a cigarette.

Satellites are launched at speeds of 30,000 km/h or more. If no other forces acted on it after the satellite was launched, it would fly far into outer space. But direct flight cannot continue, because the satellite is affected by the force of gravity of the Earth, and it begins to move in orbit around the Earth. This is how the satellite goes into orbit.

The orbit of some satellites is at a distance of 177 kilometers from the Earth, while others have no more than 35,500 kilometers. The orbit is selected by scientists in advance, taking into account the tasks assigned to the satellite.

What is a black hole?

To explain what a black hole is, we must first talk about what happens to huge stars whose mass is millions of times greater than the mass of the Sun.

All stars are born, develop, live and die. During this process, they gradually cool and shrink. And in the place where the star was located, a black hole is formed - an area with enormous gravitational field intensity. The gravity in this area is so strong that not even light can escape from it. Astronomers learn about the existence of such stars due to the fact that they emit streams of neutral particles - neutrons.

Currently, astronomers have discovered several black holes. All of them are located at a great distance from the Earth and have a mass several tens of thousands of times greater than that of the Sun.

For a long time, researchers were unclear about the properties of black holes, so many science fiction works were born that tell how a spaceship seems to fall into a “black hole” and disappear.

However, today the study of this astronomical phenomenon has begun, and let's hope that the black hole will gradually reveal all its secrets.