Satellites of planets asteroids comets meteors meteorites. Asteroids, comets, meteorites and meteors. A meteorite is a solid body of cosmic origin that has fallen to the surface of the Earth. Most found meteorites have a weight of several grams to several

On January 1, 1801, the Italian astronomer Giuseppe Piazzi, through his telescope, discovered a new celestial body that looked like a star. It and similar bodies, discovered later, were called asteroids, which means "star-like" (from the Greek words "aster" - star, "oidos" - view).

Over 5,000 asteroids have been discovered so far. Usually these are small, irregularly shaped celestial bodies with a diameter of one to several tens of kilometers.

Of course, asteroids are not stars. Like the planets, they do not emit their own light and revolve around the sun. Therefore, they are also called minor planets.

Asteroids - part solar system. Most of them move between the orbits of Mars and Jupiter.

The origin of asteroids has not yet been fully elucidated. For a long time, scientists assumed that these were the remains of some collapsed planet. But recent studies show that, most likely, these are the remains of that “building material” from which all the planets of the solar system known to us were once formed.

Comets

These celestial bodies got their name from the Greek word "cometes", which means "hairy".

Few natural phenomena frightened people like the appearance of a bright comet. It was considered a harbinger of various troubles, such as epidemics, famine, wars.

But gradually scientists accumulated knowledge about these unusual celestial bodies, and now it is known that they are part of the solar system. Comets move in elongated orbits, sometimes approaching the Sun, sometimes moving away from it.

The main part of a comet is a solid core. Its diameter is usually from 1 to 10 km. The core consists of ice, frozen gases and solid particles of some other substances.

As the comet approaches the Sun, the core heats up, and its substances begin to evaporate. A gas envelope forms around the nucleus, and then a long tail appears. A comet's tail can stretch millions of kilometers! It is always directed away from the Sun and consists of gases and fine dust. As a comet moves away from the Sun, its tail and gas envelope gradually disappear.

Over time, under the influence of solar heat, many comets are completely destroyed. Their particles are scattered in outer space.

Comets visible to the naked eye are rare.
But with the help of telescopes, scientists observe them quite often.

Meteora

A huge amount of so-called cosmic dust moves in interplanetary space. In most cases, these are the remains of collapsed comets. From time to time they burst into the Earth and flare up, sweeping across the black sky with a bright luminous line: it seems

that a star is falling. These flashes of light are called meteors (from the Greek word "meteoros" - floating in the air).

Cosmic particles are heated as a result of friction against the atmosphere, flare up and burn out. This usually happens at an altitude of 80-100 km above the Earth.

meteorites

In addition to cosmic dust, larger bodies also move in interplanetary space, mainly asteroid fragments. Getting into the Earth's atmosphere, they do not have time to burn out in it. Their remains fall on . Space bodies that have fallen to Earth are called meteorites. Meteorites are divided into three major classes: stony, iron, and stony-iron.

The fall of large meteorites to Earth is a rather rare phenomenon. Usually their mass ranges from hundreds of grams to several kilograms. The largest meteorite ever found weighed over 60 tons.

Scientists are carefully studying these space "aliens", as they allow us to judge the composition of celestial bodies, the processes taking place in space.

Mysterious Neighbors of the Sun

The largest of the asteroids - Ceres - has a diameter of about 1000 km. He was the first to open. total weight of all asteroids is about 20 times less than the mass of the moon. Despite this, they pose some danger to our planet. Scientists do not rule out that one of the asteroids may collide with the Earth. This would lead to terrible disaster. Ways are now being developed to protect the Earth from this danger.

The most famous comet, Halley's Comet, approaches the Sun once every 76 years. At this time, it flies relatively close to the Earth, and it can be observed with the naked eye. The last time people saw this comet was in 1986. Its next appearance is expected in 2062.

About 2,000 meteorites fall to Earth every year. The fall of large meteorites is accompanied by an explosion. A meteorite crater forms at the site of the explosion. One of the largest meteorite craters is located in the USA (Arizona), its diameter is 1200 m, the depth is almost 200 m.

1. In which part of the solar system do most asteroids travel?
2. What is the structure of a comet? What is its core made of?
3. How does it change appearance comet during its orbit?
4. What is a meteor; meteorite?

The solar system consists of asteroids and comets. Space dust particles and larger bodies - fragments of asteroids - move in interplanetary space. Flashes of light that occur when particles of cosmic dust burn in the earth's atmosphere are called meteors, and cosmic bodies that have fallen to Earth are called meteorites.

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Pugaeva Olga and Chernyshova Dina

Astronomy presentation on the topic "Asteroids, comets, meteorites and meteors".

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Completed the work: Pugaeva Olga and Chernyshova Dina Teacher: Malysheva V.I. MKOU "Secondary school No. 1 pos. Warm» Asteroids, comets, meteorites and meteors

Asteroids At the end of the 18th century, the German astronomers Titius and Bode independently noticed a pattern in a series of numbers expressing the average distances of the planets from the Sun. The fifth member of this series did not correspond to any planet. On January 1, 1801, the Italian astronomer Giuseppe Piazzi accidentally discovered a star whose right ascension and declination changed markedly over the course of a day of observations. Gauss calculated the orbit of this astronomical object and it became clear that a planet was discovered between Mars and Jupiter. She was named Ceres in honor of the ancient Roman goddess of fertility. In 1802, the German doctor Olbers, who was fond of astronomy, discovered near Ceres new planet called Pallas. Juno was discovered in 1804 and Vesta in 1807. Herschel suggested calling the small planets asteroids. Asteroid in Greek means "star-shaped". In 1804, Olbers expressed the famous hypothesis about the break of the hypothetical planet Phaeton between Mars and Jupiter and the formation of asteroids - its fragments. Precise definition the term "asteroid" is still not established. Until 2006, asteroids were also called minor planets.

Beginning with late XIX centuries, photography began to be used to search for asteroids. With long exposures, images of asteroids due to their rapid movement are obtained in the form of dashes. There are currently over 12,000 known asteroids. At first they were called the names of deities, then - the names famous people. Until recently, the rule was observed: to call asteroids by female names, making an exception for asteroids with unusual orbits. This rule has now been abandoned. At present, immediately after the discovery, the asteroid is assigned a preliminary designation containing the year of discovery (for example, 1937 DA), and then, if the asteroid's orbit is determined reliably, a permanent number and name. And the Olbers hypothesis had to be abandoned. Detailed mathematical calculations show that asteroids originated from the crushing of not one, but several large bodies.

At the moment, hundreds of thousands of asteroids have been discovered in the solar system. As of September 6, 2011, there were 84,993,238 objects in the databases, 560,021 had precise orbits and were given an official number. 15615 of them at that moment had officially approved names. It is assumed that in the solar system there may be from 1.1 to 1.9 million objects larger than 1 km. Most of the famous this moment asteroids is concentrated within the asteroid belt located between the orbits of Mars and Jupiter. Ceres was considered the largest asteroid in the solar system, measuring approximately 975 × 909 km, but since August 24, 2006, it has received the status of a dwarf planet.

In 1975, Clark Chapman, David Morrison, and Ben Zellner developed a classification system for asteroids based on chromaticity, albedo, and reflected spectrum characteristics. sunlight. Initially, this classification defined only three types of asteroids: Class C - carbon, 75% of known asteroids. Class S - silicate, 17% of known asteroids. Class M - metal, most of the rest. It should be borne in mind that the number of known asteroids assigned to any type does not necessarily correspond to reality. Some types are quite difficult to determine, and the type of a certain asteroid can be changed with more careful research. Classifying asteroids

The danger of asteroids At the moment there are no asteroids that could significantly threaten the Earth. The larger and heavier the asteroid, the more dangerous it poses, however, it is much easier to detect it in this case. The most dangerous at the moment is the asteroid Apophis, with a diameter of about 300 meters, in a collision with which, in the event of an accurate hit, a large city can be destroyed, but such a collision does not pose any threat to humanity as a whole. Asteroids more than 10 km across can represent a global danger. All asteroids of this size are known to astronomers and are in orbits that cannot lead to a collision with the Earth.

Comets In addition to large planets and asteroids, comets move around the Sun. Comets are the longest objects in the solar system. The word "comet" in Greek means "hairy", "long-haired". The appearance of most comets is unpredictable. People have paid attention to them since time immemorial. It is impossible not to notice in the sky a spectacle so rare, and therefore terrifying, more terrible than any eclipse, when a foggy star is visible in the sky, sometimes so bright that it can sparkle through the clouds (1577), eclipsing even the moon. And from the bowels of the uninvited heavenly guest, huge tails break out ... Aristotle in the 4th century BC. e. explained the phenomenon of the comet as follows: light, warm, "dry pneuma" (gases of the Earth) rises to the boundaries of the atmosphere, enters the sphere of heavenly fire and ignites - this is how "tailed stars" are formed. Aristotle argued that comets cause severe storms, drought. His ideas were universally recognized for two millennia. In the Middle Ages, comets were considered harbingers of wars and epidemics. So the Norman invasion of southern England in 1066 was associated with the appearance of Halley's comet in the sky. The fall of Constantinople in 1456 was also associated with the appearance of a comet in the sky.

Comets are discovered annually. On average, they open about 20 a year. About 50 comets are available for observation, and in the entire history of mankind, about two thousand comet appearances have been observed. The orbits of most comets are highly elongated ellipses. In 1702 Edmund Halley proved that the comets of 1531, 1607 and 1682 had the same orbit. It turns out that comets are back! The orbital period of Halley's Comet around the Sun is 76 years.

Comets coming from the depths of space 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 and ice, wrapped 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 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 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 "large (great) comets".

The structure of a comet As a rule, comets consist of a nucleus and a bright hazy shell (coma) surrounding it, 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 was 20 million km long. Comet C/1680 V1 had a tail stretching for 240 million km. Cases of separation of the tail from the comet have also been recorded (C/2007 N3 (Lulin)). The tails of comets do not have sharp outlines and are practically transparent - stars are clearly visible through them - as they are formed from an extremely rarefied substance (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 particles is similar to the asteroid material of the solar system, which was revealed as a result of the study of comet 81P / Wild 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.

Halley's Comet Astronomers got a comprehensive idea of ​​them thanks to successful "visits" in 1986 to Halley's comet 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 regular 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 (1784-1846) 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.

Comets and the 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 1910, for example, the Earth passed through the tail of Halley's comet, but no change in the motion of our planet occurred. 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.

Meteors and meteorites A meteorite is a body of cosmic origin that has fallen on the surface of a large celestial object. Most meteorites found have a weight of several grams to several kilograms. The largest meteorite found is the Goba (estimated to weigh about 60 tons). It is believed that 5-6 tons of meteorites fall on Earth per day, or 2 thousand tons per year.

A space body before entering the Earth's atmosphere is called a meteoroid and is classified according to astronomical features. For example, it can be cosmic dust, a meteoroid, an asteroid, their fragments, or other meteoric bodies. Flying through the Earth's atmosphere and leaving a bright luminous trail in it, regardless of whether it flies through the upper layers of the atmosphere and goes back into outer space, whether it burns up in the atmosphere or falls to the Earth, it can be called either a meteor or a fireball. Meteors are bodies no brighter than the 4th magnitude, and fireballs are considered brighter than the 4th magnitude, or bodies whose angular dimensions are distinguishable.

Classification by composition stony chondrites carbonaceous chondrites ordinary chondrites enstatite chondrites achondrites iron-stony pallasites iron mesosiderites

The most common are stone meteorites (92.8% of falls). The vast majority of stony meteorites (92.3% of stony meteorites, 85.7% of the total number of falls) are chondrites. They are called chondrites because they contain chondrules - spherical or elliptical formations of predominantly silicate composition. Most chondrules are no larger than 1 mm in diameter, but some can reach several millimeters. Chondrules are located in a detrital or finely crystalline matrix, and the matrix often differs from chondrules not so much in composition as in crystalline structure. The composition of chondrites almost completely repeats chemical composition the sun, with the exception of light gases such as hydrogen and helium. Therefore, it is believed that chondrites were formed directly from the protoplanetary cloud that surrounded and surrounds the Sun, by condensation of matter and accretion of dust with intermediate heating.

Achondrites make up 7.3% of stony meteorites. These are fragments of protoplanetary bodies that have undergone melting and differentiation in composition (into metals and silicates). Iron meteorites are composed of an iron-nickel alloy. They account for 5.7% of falls. Iron-silicate meteorites have an intermediate composition between stony and iron meteorites. They are relatively rare (1.5% of falls).

Achondrites, iron and iron-silicate meteorites are classified as differentiated meteorites. They presumably consist of matter differentiated in asteroids or other planetary bodies. Previously, it was believed that all differentiated meteorites were formed as a result of the rupture of one or more large bodies, such as the planet Phaeton. However, an analysis of the composition of various meteorites showed that they were more likely to have formed from fragments of many large asteroids.

A crater (astroblem) may form at the site of a large meteorite impact. One of the most famous craters in the world is Arizona. It is assumed that the largest meteorite crater on Earth is Wilkes Land Crater (diameter about 500 km). Earth and meteorites

Tunguska phenomenon (at the moment, it is unclear exactly the meteorite origin of the Tunguska phenomenon. For details, see the article Tunguska meteorite). Fell on June 30, 1908 in the basin of the Podkamennaya Tunguska River in Siberia. The total energy is estimated at 15.40 megatons of TNT. Tsarevsky meteorite (meteorite shower). Fell December 6, 1922 near the village of Tsarev, Volgograd region. This is a stone meteorite. The total mass of the collected fragments is 1.6 tons over an area of ​​about 15 square meters. km. The weight of the largest fallen fragment was 284 kg. Sikhote-Alin meteorite (the total mass of fragments is 30 tons, the energy is estimated at 20 kilotons). It was an iron meteorite. Fell in the Ussuri taiga on February 12, 1947. Vitim fireball. It fell near the settlements of Mama and Vitimsky in the Mamsko-Chuysky district of the Irkutsk region on the night of September 24-25, 2002. The event had a great public outcry, although the total energy of the meteorite explosion, apparently, is relatively small (200 tons of TNT, with an initial energy of 2.3 kilotons), the maximum initial mass (before combustion in the atmosphere) is 160 tons, and the final mass of fragments is about several hundred kilograms.

When large meteorites fall to Earth, large traces are left. And when falling on the planets, the craters are even larger: they are clearly visible on them.

Three meteor showers - Leonids, Andromedids and Draconids - showed very sharp bursts of activity in historical times, and in the case of Andromedids this was directly related to the destruction of Biela's comet, which split in 1845 and in the next appearance, in 1852, was visible as two faint comets separated by more than 1.5 million km. The Draconids were associated with another comet, Giacobini-Zinner. If the comet's orbit intersects the Earth's orbit, then every year, when the Earth hits the intersection point, meteor showers are observed, which increase with the simultaneous approach of the Earth and the comet's remnants to this point. If no amplification is observed, it means that the substance of the comet has more or less evenly scattered along the orbit - the comet has completely ceased to exist as a celestial body.

Minor planets, or asteroids, orbit between Mars and Jupiter and are invisible to the naked eye. The first minor planet was discovered in 1801, and by tradition it was named one of the names of Greco-Roman mythology - Ceres. Other minor planets were soon found, named Pallas, Vesta and Juno. With the use of photography, ever weaker asteroids began to be discovered. Currently, more than 2000 asteroids are known. Perhaps the asteroids arose because the substance for some reason failed to gather into one large body - the planet. For billions of years, asteroids collide with each other. This idea is suggested by the fact that a number of asteroids are not spherical, but irregular in shape. The total mass of asteroids is estimated at only 0.1 of the mass of the Earth.

The brightest asteroid - Vesta is never brighter than the 6th magnitude. The largest asteroid is Ceres. Its diameter is about 800 km, and beyond the orbit of Mars, even the strongest telescopes on such a small disk cannot see anything. The smallest known asteroids are only about a kilometer in diameter (Fig. 63). Of course, asteroids don't have an atmosphere. In the sky, small planets look like stars, which is why they were called asteroids, which means “star-like” in ancient Greek. They differ from stars only in the loop-like movement characteristic of the planets against the background of the starry sky. The orbits of some asteroids have unusually large eccentricities, as a result of which at perihelion they come closer to the Sun than Mars and even the Earth (Fig. 64). Icarus comes closer to the Sun than Mercury. In 1968, Icarus approached the Earth almost 10 times closer than Mars, but its negligible attraction had no effect on the Earth. From time to time, Hermes, Eros and other small planets come close to the Earth.

2. Fireballs and meteorites.

A rather rare phenomenon is called a bolide - a fireball flying across the sky (Fig. 65). This phenomenon is caused by the invasion of large meteoroids into the dense layers of the atmosphere, surrounded by an extensive shell of hot gases and particles formed during heating due to deceleration in the atmosphere. Fireballs often have a noticeable angular diameter in Vio of the visible diameter of the Moon and are visible even during the day. Superstitious people mistook such fireballs for flying dragons with a fire-breathing mouth. From strong air resistance, the meteoroid often breaks up and falls to the Earth with a roar in the form of fragments. A body that falls to Earth is called a meteorite.

A meteorite, which is small in size, sometimes completely evaporates in the Earth's atmosphere. In most cases, the mass of a meteorite decreases greatly during the flight. Only the remnants of a meteorite reach the Earth, usually having time to cool down when its cosmic velocity is already extinguished by air resistance. Drops out sometimes

Rice. 63. The size of one of the smallest known asteroids in comparison with the building of Moscow State University.

Rice. 64. Orbits of some asteroids with a large orbital eccentricity.

whole meteor shower. During the flight, meteorites melt and become covered with a black crust (Fig. 66). One such "black stone" in Mecca is built into the wall of the temple and serves as an object of religious worship.

There are three types of meteorites: stone, iron and iron-stone. Sometimes meteorites are found many years after they fall. Iron meteorites are especially found. In the USSR, a meteorite is the property of the state and is subject to delivery to museums for study. The age of meteorites is determined by the content of radioactive elements and lead. It is different, but the oldest meteorites are 4.5 billion years old.

Some of the largest meteorites explode at a high falling speed and form meteorite craters resembling those of the moon. The largest well-studied crater is located in Arizona (USA) (Fig. 67). Its diameter is 1200 m and its depth is 200 m.

Rice. 65. Flight of the fireball

Rice. 66. Iron meteorite.

Rice. 67. Arizona meteorite crater.

This crater appeared, apparently, about 5000 years ago. Traces of even larger and older meteorite craters have been found. All meteorites are members of the solar system.

Judging by the fact that the number of asteroids increases with decreasing size, and by the fact that many small asteroids have already been discovered that cross the orbit of Mars, it can be assumed that meteorites are very small asteroids with orbits that cross the orbit of the Earth. The structure of some meteorites indicates that they were subjected to high temperatures and pressures and, therefore, could exist in the interior of a collapsed planet or a large asteroid.

Asteroids. Meteorites. Meteora.

Asteroid

ASTEROID - a small planet-like celestial body of the solar system, moving in orbit around the sun. Asteroids, also known as minor planets, are much smaller than planets.

Definitions.

The term asteroid (from other Greek - “ starlike”) was introduced by William Herschel on the basis that these objects, when viewed through a telescope, looked like points of stars - in contrast to the planets, which, when observed through a telescope, look like disks. The exact definition of the term "asteroid" is still not established. The term "minor planet" (or "planetoid") is not suitable for the definition of asteroids, as it also indicates the location of the object in the solar system. However, not all asteroids are minor planets.

One way to classify asteroids is by size. The current classification defines asteroids as objects larger than 50m in diameter, separating them from meteoroids that look like large rocks or may be even smaller. The classification is based on the assertion that asteroids can survive entering the Earth's atmosphere and reach its surface, while meteors, as a rule, completely burn up in the atmosphere.

As a result, an "asteroid" can be defined as an object of the solar system, consisting of solid materials, which is larger than a meteor in size.

Asteroids in the solar system

To date, tens of thousands of asteroids have been discovered in the solar system. As of September 26, 2006, there were 385,083 objects in the databases, 164,612 had precise orbits and were given an official number. 14077 of them at that moment had officially approved names. It is assumed that in the solar system there may be from 1.1 to 1.9 million objects larger than 1 km. Most of the currently known asteroids are concentrated within the asteroid belt located between the orbits of Mars and Jupiter.

Ceres was considered the largest asteroid in the solar system, measuring approximately 975 × 909 km, but since August 24, 2006, it has received the status of a dwarf planet. The other two largest asteroids, 2 Pallas and 4 Vesta, have a diameter of ~500 km. 4 Vesta is the only object in the asteroid belt that can be seen with the naked eye. Asteroids moving in other orbits can also be observed during the period of passage near the Earth (eg 99942 Apophis).

The total mass of all main belt asteroids is estimated at 3.0-3.6×1021 kg, which is only about 4% of the mass of the Moon. The mass of Ceres is 0.95 × 1021 kg, that is, about 32% of the total, and together with the three largest asteroids 4 Vesta (9%), 2 Pallas (7%), 10 Hygiea (3%) - 51%, that is, the absolute majority asteroids have negligible mass.

Exploring asteroids

The study of asteroids began after the discovery of the planet Uranus in 1781 by William Herschel. Its average heliocentric distance turned out to be consistent with the Titius-Bode rule.

At the end of the 18th century, Franz Xaver von Zach organized a group of 24 astronomers. Since 1789, this group has been looking for a planet, which, according to the Titius-Bode rule, should have been at a distance of about 2.8 astronomical units from the Sun - between the orbits of Mars and Jupiter. The task was to describe the coordinates of all the stars in the area of ​​the zodiac constellations at a certain moment. In subsequent nights, the coordinates were checked, and objects that moved a greater distance were highlighted. The estimated displacement of the planet being sought must have been about 30 arc seconds per hour, which should have been easily noticed.

Ironically, the first asteroid, 1 Ceres, was discovered by the Italian Piazzi, who was not involved in this project, by chance, in 1801, on the very first night of the century. Three others - 2 Pallas, 3 Juno and 4 Vesta were discovered in the next few years - the last, Vesta, in 1807. After another 8 years of fruitless searching, most astronomers decided that there was nothing else there and stopped researching.

However, Karl Ludwig Henke persisted, and in 1830 he resumed the search for new asteroids. Five years later, he discovered Astrea, the first new asteroid in 38 years. He also discovered Hebe less than two years later. After that, other astronomers joined the search, and then at least one new asteroid was discovered per year (with the exception of 1945).

In 1891, Max Wolf was the first to use the astrophotography method to search for asteroids, in which asteroids left short light lines in photographs with a long exposure period. This method significantly increased the number of detections compared to previously used methods of visual observation: Wolf single-handedly discovered 248 asteroids, starting with 323 Brucia, while a little more than 300 were discovered before him. Now, a century later, only a few thousand asteroids have been identified, numbered and named. Much is known about them. more, however, scientists are not very worried about their study, calling asteroids "cosmic rabble" ("vermin of the skies").

Naming asteroids

At first, the asteroids were given the names of the heroes of Roman and Greek mythology, later the discoverers got the right to call it whatever they like, for example, by their own name. At first, asteroids were given predominantly female names, only asteroids with unusual orbits (for example, Icarus, approaching the Sun closer than Mercury) received male names. Later, this rule was no longer observed.

Not every asteroid can get a name, but only one whose orbit is more or less reliably calculated. There have been cases when an asteroid was given a name decades after its discovery. Until an orbit has been computed, the asteroid is given a serial number reflecting the date it was discovered, such as 1950 DA. The numbers indicate the year, the first letter is the number of the crescent in the year in which the asteroid was discovered (in the above example, this is the second half of February). The second letter indicates the serial number of the asteroid in the indicated crescent; in our example, the asteroid was discovered first. Since there are 24 crescents, and English letters- 26, two letters are not used in the designation: I (due to the similarity with the unit) and Z. If the number of asteroids discovered during the crescent exceeds 24, they return to the beginning of the alphabet again, assigning index 2 to the second letter, at the next return - 3, etc.

After receiving the name, the official naming of the asteroid consists of a number (serial number) and a name - 1 Ceres, 8 Flora, etc.

asteroid belt

The orbits of most of the numbered minor planets (98%) are located between the orbits of the planets Mars and Jupiter. Their average distances from the Sun are between 2.2 and 3.6 AU. They form the so-called main asteroid belt. All small planets, like large ones, move in a forward direction. The periods of their revolution around the Sun are, depending on the distance, from three to nine years. It is easy to calculate that line speed approximately equal to 20 km/s. The orbits of many minor planets are noticeably elongated. Eccentricities rarely exceed 0.4, but, for example, the asteroid 2212 Hephaestus has it equal to 0.8. Most of the orbits are located close to the ecliptic plane, i.e. to the plane of the Earth's orbit. The slopes are usually a few degrees, but there are exceptions. Thus, the orbit of Ceres has an inclination of 35°, and large inclinations are also known.

Perhaps, for us inhabitants of the Earth, it is most important to know the asteroids, whose orbits closely approach the orbit of our planet. There are usually three families of near-Earth asteroids. They are named after typical representatives - minor planets: 1221 Amur, 1862 Apollo, 2962 Aton. The Amur family includes asteroids whose orbits at perihelion almost touch the orbit of the Earth. The Apollos cross the Earth's orbit from the outside, their perhelion distance is less than 1 AU. The "Atonians" have orbits with a semi-major axis smaller than the earth's and cross the earth's orbit from the inside. Representatives of all these families can meet the Earth. As for close passages, they happen quite often.

For example, the asteroid Amur at the time of discovery was 16.5 million kilometers from Earth, 2101 Adonis approached 1.5 million kilometers, 2340 Hathor - 1.2 million kilometers. Astronomers at many observatories have observed the passage of asteroid 4179 Tautatis by Earth. On December 8, 1992, he was 3.6 million kilometers away from us.

Most of the asteroids are concentrated in the main belt, but there are important exceptions. Long before the discovery of the first asteroid, the French mathematician Joseph Louis Lagrange studied the so-called three-body problem, i.e. studied how three bodies move under the influence of gravitational forces. The problem is very complex and has not yet been solved in general terms. However, Lagrange managed to find that in the system of three gravitating bodies (Sun - planet - small body) there are five points where the motion of a small body is stable. Two of these points are in the orbit of the planet, forming equilateral triangles with it and the Sun.

Many years later, already in the 20th century, theoretical constructions became reality. Near the Lagrangian points in the orbit of Jupiter, about two dozen asteroids were discovered, which were given the names of the heroes of the Trojan War. Asteroids - "Greeks" (Achilles, Ajax, Odysseus, etc.) are ahead of Jupiter by 60 °, "Trojans" follow at the same distance behind. According to estimates, the number of asteroids near the Lagrange points can reach several hundred.

Dimensions and material composition

To find out the size of any astronomical object (if the distance to it is known), it is necessary to measure the angle at which it is visible from the Earth. However, it is no coincidence that asteroids are called minor planets. Even in large telescopes under excellent atmospheric conditions, using very complex, time-consuming techniques, it is possible to obtain rather fuzzy outlines of the disks of only a few of the largest asteroids. The photometric method turned out to be much more effective. There are very precise instruments that measure gloss, i.e. the stellar magnitude of the heavenly body. In addition, the illumination created by the Sun on an asteroid is well known. Other things being equal, the brightness of an asteroid is determined by the area of ​​its disk. It is necessary, however, to know how much light a given surface reflects. This reflectivity is called albedo. Methods have been developed for its determination by the polarization of light from asteroids, as well as by the difference in brightness in the visible region of the spectrum and in the infrared range. As a result of measurements and calculations, the following sizes of the largest asteroids were obtained.

The words "asteroid" and "meteorite" are often used in communication, literature, and cinema. However, not everyone fully understands the difference between these concepts.

Where do meteorites come from

From time to time, solid bodies fall to the surface of the earth from beyond its limits. They are called meteorites. In addition to the earth's surface, these objects of cosmic origin also fall on other large space objects. The places of their fall are indicated by craters, which, for example, are many on the Moon and on other planets.

Some astronomers formulate the following signs of a meteorite:

• It is a small solid object originating from a celestial body.
• Has a natural origin.
• It naturally separated from the celestial body that gave birth to it.
• Coming out from under the gravitational influence, he collided with a larger celestial body or an object of artificial origin.
• Cannot be called a meteorite if combined with a larger object.

Meteorites can vary in size and mass. Their length can start with a fraction of a millimeter and end with several meters. Can weigh from a few grams to tens of tons. Scientists have calculated that tons of extraterrestrial substances fall on our planet every day. When a cosmic body penetrates the atmosphere, glows appear, called meteors, and when many small bodies fall, a meteor shower.

A meteor at a speed of several tens of kilometers per second enters the atmosphere. Immediately it warms up and begins to glow. It burns and loses weight. As a result, a body with a mass much less than it had when approaching our planet falls to the ground.

At speeds of 25 or more kilometers per second, they almost completely disappear. Their hundreds of tons may remain an insignificant part. When a meteor body loses speed near the earth, it ceases to glow and loses temperature. During such a flight, it can collapse, which causes a meteor shower.

Sometimes the destruction of such bodies has catastrophic consequences, as was the case with Tunguska meteorite. When a meteorite hits the surface of the earth at high speed, an explosion occurs and a rounded crater is formed. At relatively low speeds of hundreds of meters per second, the meteorite can survive, and the size of the crater will not be much larger than the meteorite itself. Several large craters with a diameter of one to three hundred kilometers are known on the surface of our planet.

Meteorites found on Earth have certain characteristics. They usually have an irregular shape, a melting crust, characteristic depressions on the surface that look like fingerprints, and magnetic properties. Most often, meteorites fall on the planet, which are stones (92.8%), as well as iron and containing iron with a stone.

What is an asteroid

A dozen years ago they were called minor planets. Today, the term "asteroid" refers to bodies rotating in the solar orbit, the length of which exceeds 30 meters. Their shape is wrong, they have no atmosphere. Asteroids meet with their satellites. The emergence of large asteroids with a diameter of more than 120 km is associated with the development of Jupiter. It is believed that asteroids were formed in the process of increasing the mass of celestial bodies due to the gravitational attraction of gas and other matter to them from the outer space surrounding these bodies. Smaller asteroids appeared as fragments from collisions between asteroids. Most of the asteroids known to science are concentrated in the asteroid belt, which is located in the region between Jupiter and Mars.

According to some estimates, the number of asteroids larger than a kilometer located within the solar system can be up to 1.9 million units. Almost 670,500 asteroids have been recorded revolving around the Sun. The orbits of most of them are determined, they have official numbers, and over 19 thousand asteroids have received officially fixed names. To do this, their orbit had to be reliably calculated. The largest asteroids are Ceres, Pallas, Vesta, Apophis and Hygiea. Some of them can be observed with the naked eye during the passage of the Earth. According to calculations, the entire mass of asteroids in the main belt does not reach four percent of the mass of the Moon.

Scientists around the world have been exploring asteroids since the 18th century. Various methods have been used for this. In 1991, a space probe transmitted an image of the asteroid Gaspra. In 2010, they discovered water ice and complex hydrocarbons on one of the largest asteroids. This opens up opportunities for understanding the origin of water and life on our planet. In 2016, the Americans launched interplanetary station, which in 2019 should receive soil samples from the asteroid Benu and deliver them to Earth in 2023. Such celestial bodies are classified according to the characteristics of their orbits and the degree to which sunlight is reflected by their surface.

They can pose a huge danger when colliding with the Earth. Even the impact of an asteroid 50 meters in diameter can cause an explosion, as in the fall of the Tunguska meteorite. It will lead to numerous victims and huge economic losses. To destroy human civilization, a collision with a three-kilometer asteroid is enough. Powerful telescopes operate in Russia and other countries to detect dangerous celestial bodies.

Are there any differences

A meteorite is considered to be predominantly a small celestial body, partially burned up in the Earth's atmosphere. They move randomly in space. Most often, an insignificant part of the meteorite reaches the Earth's surface. Every day, several tons of different meteorites fall to the ground in aggregate. Their number cannot be measured.

An asteroid is a relatively small celestial body that revolves in a stationary orbit around the Sun. He may have his companions. Under the influence of gravity, the orbit of an asteroid can change. Most large asteroids have their registration numbers and even names. Scientists systematically study them. Large asteroids can pose a danger to humanity.