Fireballs and meteorites. Abstract: Asteroids, meteorites, meteors Meteorites celestial bodies

Wikipedia

Asteroid belt

Classification by composition

stone

chondrites

carbonaceous chondrites

ordinary chondrites

enstatite chondrites

achondrites

iron-stone

pallasites

mesosiderites

iron

Wikipedia

Interesting Facts

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An asteroid is a relatively small celestial body in the Solar System moving in orbit around the Sun. Asteroids are significantly smaller in mass and size than planets, have an irregular shape, and do not have an atmosphere, although they may also have satellites.

The term asteroid (from ancient Greek ἀ στεροειδής - “like a star”, from ἀ στήρ - “star” and εῖ̓ δος - “appearance, appearance, quality”) was introduced by William Herschel on the basis that these objects, when observed in the 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. Until 2006, asteroids were also called minor planets.

The main parameter by which classification is carried out is body size. Asteroids are considered bodies with a diameter of more than 30 m; smaller bodies are called meteoroids.

Currently, 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 precisely defined orbits and were assigned an official number. 15,615 of them at this time had officially approved names. It is estimated that there may be from 1.1 to 1.9 million objects in the Solar System that are larger than 1 km. Most currently known asteroids are concentrated within the asteroid belt, located between the orbits of Mars and Jupiter.

Wikipedia

Asteroid belt

The orbits of 98% of the numbered asteroids are located between the orbits of Mars and Jupiter. Their average distances from the Sun range from 2.2 to 3.6 astronomical units. They form the so-called main asteroid belt. All asteroids, like large planets, 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 the linear speed is approximately 20 km/s. The orbits of many asteroids are noticeably elongated. Eccentricities rarely exceed 0.4. Most orbits are located close to the ecliptic plane, i.e., to the plane of the Earth's orbit. Tilts are usually a few degrees, but there are exceptions. Thus, the orbit of Ceres has an inclination of 35°, and greater inclinations are also known. If on a model of the Solar System the orbits of asteroids are depicted with wire rings, you will get a loose openwork torus of ellipses chaotically intertwined in space.

Ceres, measuring approximately 975×909 km, was considered the largest asteroid in the Solar System, but since August 24, 2006, it 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 observed with the naked eye. Asteroids moving in other orbits can also be observed during their passage near the Earth (see, for example, (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 9.5·1020 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 vast majority of asteroids have an insignificant mass by astronomical standards.

At first, asteroids were given the names of heroes of Roman and Greek mythology, later discoverers received the right to call them whatever they wanted - 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 any asteroid can receive a name, but only one whose orbit has been more or less reliably calculated. There have been cases when an asteroid received a name decades after its discovery. Until the orbit is calculated, the asteroid is given a serial number reflecting the date of its discovery, for example, 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 example given, this is the second half of February). The second letter indicates the serial number of the asteroid in the specified crescent; in our example, the asteroid was discovered first. Since there are 24 crescents and 26 English letters, 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 again return to the beginning of the alphabet, assigning the second the letter index is 2, on the next return - 3, etc.

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

A meteoroid, or meteoroid, is a celestial body intermediate in size between interplanetary dust and an asteroid. Flying at a tremendous speed (11-72 km/s) into the Earth’s atmosphere, due to friction, it heats up greatly and burns, turning into a luminous meteor or fireball, which can be seen as a “shooting star”. The visible trace of a meteoroid entering the Earth's atmosphere is called a meteor, and a meteoroid falling on the Earth's surface is called a meteorite.

According to the official definition of the International Meteor Organization (IMO), a meteoroid is a solid object moving in interplanetary space, much smaller in size than an asteroid, but much larger than an atom. The British Royal Astronomical Society put forward a different formulation, according to which a meteoroid is a body with a diameter of 100 microns to 10 m. Other sources limit the size of a meteoroid to 50 m.

Cosmic dust is formed in space by particles ranging in size from a few molecules to 0.1 mm. 40 kilotons of cosmic dust settle on planet Earth every year.

Cosmic dust can also be distinguished by its astronomical position, for example: intergalactic dust, interstellar dust, circumplanetary dust, dust clouds around stars and the main components of interplanetary dust in our zodiacal dust complex (observed in visible light as zodiacal light): asteroid dust, comet dust and some minor additions: Kuiper Belt dust, interstellar dust passing through the Solar System, and beta meteoroids.

In the Solar System, dust matter is not evenly distributed, but is concentrated mainly in dust clouds (inhomogeneities) of different sizes. This was established during a total solar eclipse on February 15, 1961, using optical equipment installed on a probe rocket of the Institute of Applied Geophysics to measure the brightness of the outer corona in the altitude range 60-100 km above the Earth's surface.

A meteorite is a body of cosmic origin that fell on the surface of a large celestial object.

Most meteorites found weigh between a few grams and several kilograms. The largest meteorite found was Goba (which was estimated to weigh about 60 tons). It is believed that 5-6 tons of meteorites fall to the Earth per day, or 2 thousand tons per year.

The existence of meteorites was not recognized by leading academicians of the 18th century, and hypotheses of extraterrestrial origin were considered pseudoscientific. It is alleged that the Paris Academy of Sciences in 1790 decided not to consider future reports of rocks falling to the Earth as an impossible phenomenon. In many museums, meteorites (in the terminology of that time - aerolites) were removed from collections so as not to “make museums a laughing stock.”

Academicians V.I. Vernadsky, A.E. Fersman, well-known meteorite research enthusiasts P.L. Dravert, L.A. Kulik and many others were involved in the study of meteorites. The Russian Academy of Sciences now has a special committee that supervises the collection, study and storage of meteorites. The committee has a large meteorite collection.

Classification by composition

stone

chondrites

carbonaceous chondrites

ordinary chondrites

enstatite chondrites

achondrites

iron-stone

pallasites

mesosiderites

iron

The most common meteorites are stony meteorites (92.8% of falls). They consist mainly of silicates: olivines (Fe, Mg)2 (from fayalite Fe2 to forsterite Mg2) and pyroxenes (Fe, Mg)2Si2O6 (from ferrosilite Fe2Si2O6 to enstatite Mg2Si2O6).

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

Achondrites make up 7.3% of stony meteorites. These are fragments of protoplanetary (and planetary?) bodies that have undergone melting and differentiation by 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 a composition intermediate between stony and iron meteorites. They are relatively rare (1.5% incidence).

Achondrites, iron and iron-silicate meteorites are classified as differentiated meteorites. They presumably consist of matter that has undergone differentiation in the composition of 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 Phaethon. However, an analysis of the composition of various meteorites showed that they were more likely formed from the debris of many large asteroids.

Previously, tektites, pieces of siliceous glass of impact origin, were also isolated. But later it turned out that tektites are formed when a meteorite hits rock rich in silica.

Classification by detection method

falls (when a meteorite is found after observing its fall in the atmosphere);

finds (when the meteorite origin of the material is determined only by analysis).

Wikipedia

Interesting Facts

Scientists have studied the Yamato 691 meteorite. This object was discovered in 1969 in Antarctica, becoming one of the first meteorites found on this continent. The scientists' analysis showed that the meteorite is the remains of a celestial body 4.5 billion years old, whose orbit lay between Mars and Jupiter. Using an electron microscope, scientists discovered small inclusions of a new mineral on the surface of the meteorite. The size of the wassonite particles found was 50 by 450 nanometers. According to the researchers, wassonite most likely does not occur on Earth.

A flash drive made from a meteorite was shown in Poland. The manufacturer claims that the body of the gadget is made of African ebony (one of the most valuable types of wood), and decorated with a piece of a real meteorite, diamond and 18-karat gold (or 925 silver). The cost of the gadget is also cosmic. The version with silver inserts will cost the buyer $1,130, while the “gold with meteorite” version costs $2,000.

The discovery of a meteorite is a fairly rare occurrence. The Meteoritics Laboratory reports: “In total, only 125 meteorites have been found on the territory of the Russian Federation over 250 years.”

Murchison (Murchison meteorite) is a carbonaceous meteorite with a total weight of 108 kilograms. Fell near the village of Murchison, Victoria, Australia, September 28, 1969. It is interesting because it contains a large number of organic inclusions. In particular, studies in 2008 showed the presence of nucleic bases. Buildings were damaged during the fall. It also became known because of the fossil particles of filamentous microorganisms discovered in it, reminiscent of lower fungi and retaining details of their cellular structure, as well as the fossilized remains of certain bacteria.

The Health and Safety Executive (HSE) at the British Atomic Energy Authority came up with an equation. According to it, approximately once every 7 thousand years some unfortunate Briton will be flattened by a celestial body.

Scientists consider Antarctica to be a real repository of meteorites. This inaccessible continent has changed little for many hundreds of thousands of years. Since 1969, researchers from the United States and Japan have collected more than 20,000 meteorite fragments from the Antarctic mountainous regions, where they lay buried under snow layers for thousands of years. In Antarctica, almost all meteorites can be collected, even if this piece of space debris measures a few millimeters in diameter.

Photo: meteorite from Namibia. Named at the auction “The Scream” for its resemblance to the famous painting by Edvard Munch.

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Meteorites and asteroids

What are asteroids and meteorites?

A meteorite is a body of cosmic origin that fell onto the surface of a large celestial object.

An asteromid is a relatively small celestial body in the Solar System, moving in orbit around the Sun. Asteroids are significantly smaller in mass and size than planets, have an irregular shape, and do not have an atmosphere, although they may also have satellites.

Where do meteorites come from?

Meteorites are of great value to science. Before the start of the space age, they were the only ones that made it possible to directly study extraterrestrial matter in a laboratory.

The planets on their way seem to scoop up interplanetary “garbage”. At the same time, the Solar system is replenished with new portions of it as a result of collisions with each other and crushing of asteroids and comets. It is possible that new meteoroid bodies are also born due to the bombardment of small planets by comets coming from the outskirts of the solar system. The trajectories of fragments of asteroids and comets can differ greatly from the orbits of their parent bodies. That is why countless cosmic dust particles, grains of sand, stones and blocks are moving in interplanetary space in various orbits today. Astronomers call all this “trifle” with a diameter from fractions of a millimeter to several meters meteoroids or meteoroids. The orbits of some of them intersect with the earth's, and sometimes meteoroids invade the atmosphere of our planet at speeds of tens of kilometers per second.

Asteroid formation

Astronomers have always wondered: why is there such a large distance between the orbits of Mars and Jupiter? They spent three decades trying to find a new planet in this gap. On January 1, 1801, at an observatory on the island of Sicily, astronomer Giuseppe Piazzi saw a small star in the sky that had not previously been in this place, and it was moving.

The orbit of this nimble object was calculated and found that it was beyond the orbit of Mars. The planet was named Ceres, after the ancient Roman goddess of fertility.

Soon another small stellar body was discovered next to it, which was named Pallas. William Herschel proposed calling the new ones “star-like” asteroids.

Of the thousands of asteroids, only 98% orbit the Sun between the orbits of Mars and Jupiter. Due to the influence of giant Jupiter, some groups of asteroids can come close to the Earth's orbit. However, today the Solar System is a very old and “balanced object”, and all the cataclysms that were supposed to happen have already happened.

How did asteroids form? According to one hypothesis, they are the remains of the planet Phaeton, destroyed by gravitational disturbances. But in fact, the total mass of all celestial bodies in the asteroid belt does not exceed 4% of the mass of the Moon. Modern theories claim that the asteroid belt is a product of gravitational disturbances of Jupiter, which created a kind of cosmic “meat grinder” beyond the orbit of Mars.

There are asteroids in the solar system beyond the orbit of Jupiter. They are concentrated in the so-called Kuiper belt, which is much wider and more massive than the asteroid belt beyond the orbit of Mars.

INTERESTING! Asteroids are formed by collisions. Almost every object in space, including the Earth, was formed in some way by a collision. Every celestial body has at least two craters on its surface. These collisions can destroy an asteroid or cause asteroids to merge. The collision may cause changes in orbit - rotation or axial tilt. There is no way to know exactly how many asteroids there were 100 million years ago and how many more there will be from such interactions and collisions.

When was the first meteorite (asteroid) noticed?

First asteroid - Ceres

1) The first: Ceres - was discovered at the very beginning of the 19th century. Following it, several more similar small celestial bodies were discovered moving far from the Earth - between the orbits of Mars and Jupiter. And at the very end of the century, the first asteroid was found, the path of which ran relatively close to the earth’s orbit. And then the idea of a collision began to take on visible features. The fact is that the nature of the movement of this asteroid, which first received the number 433 and later the name Eros, turned out to be unusual. Unlike its predecessors, located far from the earth - between Mars and Jupiter, it moved in such a way that its path crossed the orbit of Mars and approached the orbit of the Earth closer than the orbits of neighboring large planets. The minimum distance between Eros and Earth turned out to be 22.5 million km.

In 1932, the Apollo asteroid was discovered, the orbit of which, as it turned out, not only approached the earth’s, but even crossed it. And after another 5 years, the Earth almost collided with the Hermes asteroid, which flew at a distance only 1.6 times greater than the “location” of the Moon. This small asteroid, 800 m in diameter, was noticed by astronomers only a few days before approaching the Earth, so it was not possible to accurately determine its orbit, and soon it completely disappeared from view. Scientists do not exclude its re-passage near our planet, but now it is unlikely to become as unexpected, since astronomers from different countries are constantly observing asteroids approaching the Earth.

More than 500 space objects with similar orbits are now known. They, called near-Earth asteroids or near-Earth asteroids, are relatively small - only the two largest of them reach 30-40 km in diameter. It is believed that in addition to them, there are also many small objects that are not yet accessible to detection with a telescope. The total number of near-Earth asteroids is currently “estimated” at 5,000.

Falls of celestial bodies have been described since ancient times, but the first meteorite whose fall was officially recorded dates back to 1492. A stone weighing 126 kg fell on the Upper Rhine in the town of Ensisheim. By order of the Holy Roman Emperor Maximilian, he was chained to the wall of the city temple, “so that he could not fly back into the sky.” In total, since then, the fall of just over 1.1 thousand meteorites has been reliably recorded, and over 5 thousand have been found. At the same time, the death of a person has never been documented. There are only two known cases of people being injured by meteorites - in 1954 in the USA and in 2004 in the UK.

The danger of meteorites and asteroids

Let us remember the existence of such heavy gas giants as Jupiter and Saturn. It was they who played the role of “defenders” of the Earth from an external threat - dangerous asteroids, deflecting them and attracting them to themselves with their strong gravitational fields. Thus, those celestial bodies that could have interrupted the entire development of life on our planet in an instant simply did not reach it.

Most of the asteroids did not reach the Earth, while some still fell on the surface of the planet. This phenomenon is spoken of as a meteorite threat, a threat to the existence of earthly life. The most famous manifestation of such a threat was the meteorite that fell to Earth about 65 million years ago, which led to a radical change in all life on the planet, putting an end to the era of dinosaurs. Geological evidence for this reason is that throughout the planet there is a layer of clay with a high content of iridium, a substance very rare on Earth, but quite common in meteorites. Based on this, we can assume the following scenario for that disaster: a falling meteorite upon impact raised a huge amount of dust into the atmosphere, which blocked sunlight for several years. As a result, the plants died first, and after them the dinosaurs that fed on them... But how relevant is the meteorite threat now, in our days? Let's give a simple example from modern reality: on June 7, 2006, a large meteorite fell in northern Norway. Astronomers estimate its mass at only a thousand kilograms, while the destruction it caused is comparable to the explosion of the atomic bomb dropped on Hiroshima. What would happen if this meteorite fell not in a deserted area, but on a large city? The consequences of such a fall would be dire. A catastrophe would have occurred even when the meteorite fell not on land, but in the sea - in this case, a tsunami wave would have formed, destroying coastal areas where millions of people live.

Despite the destruction caused by the falls of the “heavenly guests,” science does not know of a case where they killed a person. The only person hit by the meteorite today is a woman from Australia. In 1954, a 3.2 kg stone fell on her house, injuring her shoulder.

meteorite asteroid

Interesting facts about meteorites and asteroids

1. Asteroids and planets celebrate their birthday together. The process that helped form the planets is called augmentation. At the beginning of the universe, if two bodies collided, they would form a larger body. Planets and asteroids were formed in this manner. Apparently the planets accumulated more mass than most asteroids. But as noted with the Ceres asteroid, which is a dwarf planet, some asteroids are very close to gaining enough mass to have the gravity to transition to planetary status.

2. The asteroid is made of various materials. Asteroids are made from various minerals and substances. Their composition depends on the planet they struck upon impact, and also on the chemical reactions they may have experienced as they circled the solar system. The asteroids closest to the Sun are mostly carbonaceous, while those further away are composed of silicate rock. Metallic asteroids are made of 80% iron and the rest is nickel combined with many other mixed metals such as iridium, palladium, platinum and gold. Some are also made of half silicate and half metal.

3. Most asteroids are covered with dust. This dust is called regolith. This is more of a rocky rubble, such dust and is the result of constant collisions between asteroids and any other body that crosses their path. The larger object wins and is covered in rubble from the losing object in this fight.

4. An asteroid may have killed the dinosaurs. The Chicxulub crater is thought to be 65 million years old. He may be the source of climate change that led to the extinction of all dinosaurs. One can imagine the debris and clouds of dust that must have been thrown into the air in the wake of this asteroid, large enough to create a crater that is more than 180 km in diameter. Those dinosaurs that did not die immediately probably suffered from starvation before their death.

5. Asteroids have satellite moons. The Galileo spacecraft proved this point back in 1993 when it examined the flight of asteroid 243 (Ida) and discovered its lunar dactyl. This was the first non-planet object found with its own "moon". Since then, several other similar objects have been discovered, but the first discovery was the most exciting for astronomy.

Here are just a few interesting facts about asteroids. Some of the craters on Earth have been developed as sources of minerals. Sudbury is now one of the largest mining communities in the world. The incident near the Tunguska River in Siberia is believed by astronomers to be the latest impact of an asteroid on Earth.

Meteorites

The very first mentions

Our ancestors have long known about the fall of meteorites on the planet. The ancient Greek philosophers Anaxagoras and Diogenes wrote about these events. By the way, in the first millennium BC, the Romans even minted images of meteorites on their coins.

In Russian chronicles, the fall of the “heavenly stones” was first mentioned in 1091. An entry from the Laurentian Chronicle reads: “In the same summer, Vsevolod caught wild animals outside Vyshegorod, sweeping the net and shouting, the great serpent fell from heaven, terrified all the people. At the same time I will strike the earth, as if I heard many people...”

The oldest. The oldest known meteorite was discovered in China in the city of Xi'an. The two-ton alien fell to earth about 1.9 billion years ago.

The biggest. In 1920, a meteorite weighing 60 tons, called Goba, fell in Namibia. It consists entirely of iron and is the heaviest of all that have found refuge on Earth.

The most mysterious. To this day, the most mysterious case of a meteorite falling to earth is undoubtedly the Tunguska phenomenon. According to one version, a certain body of cometary origin caused an air explosion that occurred in the area of the Podkamennaya Tunguska River on June 30, 1908. The total energy of the explosion is estimated at 40-50 megatons of TNT, which corresponds to the energy of the most powerful hydrogen bomb! A generally accepted hypothesis explaining all the features of this phenomenon has never been proposed. At the moment, there are about 120 versions of the explanation of what happened.

The strongest meteor showers. This happened on the night of November 12-13, 1833. The rain continued continuously for 10 hours. During this time, approximately 240 thousand large and small meteorites fell on the Earth's surface.

The largest collection of meteorites on Earth. For meteorite hunters, the ideal place is the ice shell of Antarctica, which preserves their black traces against its white background. According to experts, approximately 700 thousand are scattered inside and on the surface! The largest accumulation of meteorites on a limited area of the surface of Antarctica was discovered in 1979. According to the popular magazine New Scientist, “meteorites are literally lying underfoot.”

The largest collection of meteorites in the world. A rich collection is collected in the Mining Museum of St. Petersburg. The exhibits include more than 300 celestial aliens. The largest specimen on display is a 450-kilogram piece of the aforementioned giant Sikhote-Alin meteorite, which crumbled into pieces over the Ussuri taiga in 1947.

The most unexpected meteorite discovery. A certain Hawthorn, an amateur astronomer, built a private observatory on his estate near Washington. His favorite pastime was watching falling celestial bodies. In January 1955, he heard a sound like an explosion. Running into the observatory, Gavthorn saw two smoking fragments on his chair. They turned out to be meteorites. One of the fragments weighed 1192 grams, the other - 1132. The heavenly stones consisted of pure iron.

Symbolic meteorite fall. On September 5, 1812, on the eve of the Battle of Borodino, a meteorite fell in the camp of a Russian artillery battery near the village of Gorki, as if announcing an upcoming victory. He was picked up by a sentry and handed over to his commander Dietrichs. Then the find was kept in his family for a long time, and only in 1892 his descendants transferred it to the Russian Academy of Sciences.

The most useful "alien". The first iron used by man was meteorite. This is reflected in the names of many peoples. Thus, the ancient Egyptians called it “binipet”, which means heavenly ore. In ancient Mesopotamia it was called "anbar" - heavenly metal; The ancient Greek "sideros" comes from the Latin word - starry. The ancient Armenian name for iron is “erkam” - fallen from the sky.

Literature

1. http://sky24.ru/analytics

2. http://starmission.ru/blog/planetary_system

3. http://skybox.org.ua/interesnye-fakty-ob-asteroidakh

4. http://galspace.spb.ru/nature.file/osvoenie.html

5. http://www.ronl.ru/referaty/astronomiya/13155/

6. http://www.kommersant.ru/doc/2129498

7. http://www.xn--80audhgvl.xn--p1ai/

8. http://ru.wikipedia.org

9. http://www.mgdvorec.ru

10. http://www.meteorite.narod.ru

11. http://www.astrogalaxy.ru/061.html

12. http://www.coolreferat.com/

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Asteroids. Meteorites. Meteors.

Asteroid

ASTEROID is a small planet-like celestial body in the Solar System moving in orbit around the Sun. Asteroids, also known as minor planets, are significantly smaller in size than planets.

Definitions.

The term asteroid (from ancient Greek - “like a star”) was introduced by William Herschel on the basis that these objects, when observed through a telescope, looked like points of stars - in contrast to planets, which when observed through a telescope, looked like disks. The exact definition of the term "asteroid" is still not established. The term “minor planet” (or “planetoid”) is not suitable for defining asteroids, since 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 with a diameter greater than 50 m, separating them from meteoroids, which look like large rocks or may be even smaller. The classification is based on the assertion that asteroids can survive entry into the Earth's atmosphere and reach its surface, while meteors, as a rule, burn up completely in the atmosphere.

As a result, an “asteroid” can be defined as a solar system object made of solid materials that is larger than a meteor.

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 precisely defined orbits and were assigned an official number. 14,077 of them at this time had officially approved names. It is estimated that the Solar System may contain from 1.1 to 1.9 million objects larger than 1 km. Most currently known asteroids are concentrated within the asteroid belt, located between the orbits of Mars and Jupiter.

Ceres, measuring approximately 975×909 km, was considered the largest asteroid in the Solar System, but since August 24, 2006, it 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 observed with the naked eye. Asteroids moving in other orbits can also be observed during their passage near the Earth (for example, 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 Hygea (3%) - 51%, that is, the absolute majority asteroids have negligible mass.

Asteroid exploration

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

At the end of the 18th century, Franz Xaver von Zach organized a group that included 24 astronomers. Since 1789, this group has been searching for a planet that, according to the Titius-Bode rule, should be located 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 stars in the area of zodiacal constellations at a certain moment. On subsequent nights, the coordinates were checked and objects that had moved greater distances were identified. The estimated displacement of the desired planet should have been about 30 arcseconds per hour, which should have been easy to notice.

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

However, Karl Ludwig Henke persisted, and in 1830 he resumed the search for new asteroids. Five years later, he discovered Astraea, the first new asteroid in 38 years. He also discovered Hebe less than two years later. After this, 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 visual observation methods: Wolff single-handedly discovered 248 asteroids, starting with 323 Brutius, while little more than 300 had been discovered before him. Now, a century later, only a few thousand asteroids have been identified, numbered and named. There are many more of them known, but scientists are not very worried about studying them, calling asteroids the “vermin of the skies.”

Asteroid naming

At first, the asteroids were given the names of heroes of Roman and Greek mythology, later the discoverers received the right to call it whatever they wanted, 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.

After receiving a 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 the majority of the numbered minor planets (98%) are located between the orbits of the planets Mars and Jupiter. Their average distances from the Sun range from 2.2 to 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 range from three to nine years, depending on the distance. It is easy to calculate that the linear speed is approximately 20 km/s. The orbits of many small planets are noticeably elongated. Eccentricities rarely exceed 0.4, but, for example, for asteroid 2212 Hephaestus it is 0.8. Most orbits are located close to the ecliptic plane, i.e. to the plane of the Earth's orbit. Tilts 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 are close to 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 Aten. The Amur family includes asteroids whose orbits at perihelion almost touch the orbit of the Earth. The Apollo missions cross the Earth's orbit from the outside, their perhelion distance is less than 1 AU. "Atonans" have orbits with a semi-major axis smaller than the Earth's and intersect the Earth's orbit from the inside. Representatives of all these families can meet with the Earth. As for close passes, they happen quite often.

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

The majority of 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. investigated how three bodies move under the influence of gravity. The problem is very complex and in general terms has not yet been solved. However, Lagrange managed to find that in the system of three gravitating bodies (Sun - planet - small body) there are five points where the movement of the small body turns out to be 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. The “Greeks” asteroids (Achilles, Ajax, Odysseus, etc.) are 60° ahead of Jupiter, the “Trojans” follow at the same distance behind. It is estimated that the number of asteroids near 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 with large telescopes under excellent atmospheric conditions, using very complex, labor-intensive techniques, it is possible to obtain rather vague 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 accurate instruments that measure gloss, i.e. stellar magnitude of the celestial body. In addition, the illumination created by the Sun on an asteroid is well known. All other things being equal, the brightness of an asteroid is determined by the area of its disk. It is, however, necessary to know what fraction of the light a given surface reflects. This reflectivity is called albedo. Methods have been developed for its determination by the polarization of asteroid light, 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 onto the surface of the earth from beyond its boundaries. They are usually called meteorites. In addition to the earth's surface, these objects of cosmic origin also fall on other large space objects. The places where they fell are indicated by craters, of which, for example, there are many on the Moon and other planets.

Some astronomers formulate the following signs of a meteorite:

It is a small solid object originating from a celestial body.
It is of natural origin.
Naturally separated from the celestial body that gave birth to it.
Coming out of 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 begin with fractions of a millimeter and end with several meters. Can weigh from several 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 called meteors appear, and when many small bodies fall, meteor showers appear.

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

At speeds of 25 kilometers per second or more, they almost completely disappear. Hundreds of tons of them may remain an insignificant part. When a meteoroid near the ground loses speed, it stops glowing and loses temperature. During such a flight, it can be destroyed, 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 earth's surface at high speed, an explosion occurs and a round crater is formed. At relatively low speeds of hundreds of meters per second, the meteorite can be preserved, and the crater in size will not be much larger than the meteorite itself. Several large craters with a diameter ranging from one to three hundred kilometers are known on the surface of our planet.

Meteorites found on Earth have certain characteristics. They typically have an irregular shape, a melting crust, characteristic fingerprint-like indentations on the surface, and magnetic properties. Most often, meteorites that fall on the planet are stones (92.8%), as well as iron meteorites and those containing iron and stone.

What is an asteroid

Just a decade ago they were called minor planets. Today, the concept of “asteroid” refers to bodies rotating in solar orbit whose length exceeds 30 meters. Their shape is irregular, 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 from the outer space surrounding these bodies. Smaller asteroids appeared as debris 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 may be up to 1.9 million units. It has been recorded that almost 670 and a half thousand asteroids revolve around the Sun. The orbits of most of them have been determined, they have official numbers, and over 19 thousand asteroids have received officially recorded names. To do this, their orbit had to be reliably calculated. The largest asteroids are considered to be Ceres, Pallas, Vesta, Apophis and Hygiea. Some of them can be observed with the naked eye as they pass by the Earth. According to calculations, the entire mass of the main belt asteroids does not reach four percent of the mass of the Moon.

Scientists around the world have studied 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 possibilities for understanding the origins of water and life on our planet. In 2016, the Americans launched an interplanetary station, which in 2019 should receive soil samples from the Benu asteroid 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 if they collide with the Earth. Even the impact of an asteroid 50 meters in diameter can cause an explosion like the fall of the Tunguska meteorite. It will lead to numerous casualties and huge economic losses. A collision with a three-kilometer asteroid is enough to destroy human civilization. In Russia and other countries, powerful telescopes operate to detect celestial bodies that pose a danger.

Are there any differences

A meteorite is considered to be primarily a small celestial body that has partially burned up in the Earth's atmosphere. They move chaotically in space. Most often, an insignificant part of the meteorite reaches the Earth's surface. Several tons of different meteorites fall to the ground every day. Their number is impossible to measure.

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

Minor planets – asteroids (Greek asteroedeis - star-like) have nothing in common with stars, and are named so only because they are visible through a telescope as point objects. The history of the discovery of small planets is interesting. By the end of the 18th century. the empirical law of planetary distances was known (the so-called Titius-Bode rule), according to which there should have been another unknown planet between Mars and Jupiter. The search for it led the astronomer Piazzi to the discovery in 1801 of the planet Ceres with a diameter of 1003 km. The discovery of three more planets: Pallas - 608 km, Juno - 180 km and Vesta - 538 km - was unexpected. In recent years, asteroids up to 1 km in diameter have been discovered, and their total number reaches several thousand. Since asteroids move, during long photographic exposures they appear as bright white lines against a black background of the starry sky.

Observations have shown that asteroids have an irregular polyhedral shape and move in orbits of various shapes - from circles to highly elongated ellipses; the vast majority of them (98%) are contained between the orbits of Mars and Jupiter (“the main asteroid belt”), but the asteroid Icarus approaches the Sun closer than Mercury, and some move away as far as Saturn. The orbits of most asteroids are concentrated near the ecliptic plane; their circulation periods range from 3.5 to 6 years; they are assumed to rotate around their axes (based on the periodic change in apparent brightness). Based on their material composition, asteroids are divided into stony, carbonaceous and metallic asteroids.

The total mass of all asteroids is estimated at 0.01 Earth masses. Their common attraction does not cause noticeable disturbances in the movement of Mars and other planets.

The orbits of some asteroids intersect with the orbit of the Earth, but the probability of the Earth and an asteroid simultaneously being at the same point and colliding is extremely small. It is believed that 65 million years ago, a celestial body such as an asteroid fell to Earth in the area of the Yucatan Peninsula and its fall caused clouding of the atmosphere and a sharp decrease in the average annual air temperature, which affected the Earth's ecosystem.

Currently, astronomers are concerned about the unusual “invasion” of large celestial bodies in the vicinity of the planets of the solar system. So, in May 1996, two asteroids flew at a short distance from the Earth. Many experts suggest that the solar system fell into a kind of trail of large celestial bodies formed outside our system, and therefore believe that, along with the nuclear threat, the number one danger for our planet has become the danger posed by asteroids. A new important problem has arisen - the creation of space protection of the Earth from asteroids, which should include both ground-based and space-based assets, including those located in deep space. The creation of such a system should be carried out on an international basis.

On the other hand, the increase in the number of visible asteroids can be explained by the increase in the volume of astronomical information in recent years, after observations were transferred from the Earth's surface to near space.

On the issue of the origin of asteroids, two directly opposing points of view have been expressed. According to one hypothesis, asteroids are fragments of a large planet (it was called Phaethon), located between Mars and Jupiter at the site of the main asteroid belt and split apart as a result of a cosmic catastrophe due to the powerful gravitational influence of Jupiter. According to another hypothesis, asteroids are protoplanetary bodies that arose due to the thickening of the dust environment, which could not unite into a planet due to the disturbing action of Jupiter. In both cases, the “culprit” turns out to be Jupiter.

Comets (Greek cometes - long-haired) - small bodies of the Solar System, moving in highly elongated elliptical or even parabolic orbits. Some comets have perihelia near the Sun and aphelion outside Pluto. The movement of comets in orbits can be either forward or backward. The planes of their orbits lie in different directions from the Sun. The orbital periods of comets vary greatly: from several years to many thousands of years. A tenth of the known comets (about 40) appeared more than once; they are called periodic.

Comets have a head and a tail. The head consists of a hard core and coma. The core is an ice conglomerate of frozen gases (water vapor, carbon dioxide, methane, ammonia, etc.) with an admixture of refractory silicates, carbon dioxide and metal particles - iron, manganese, nickel, sodium, magnesium, calcium, etc. It is assumed that the core contains organic molecules. Comet nuclei are small, their diameter ranges from several hundred meters to several (50 – 70) kilometers. Coma is a gas-dust environment (hydrogen, oxygen, etc.), glowing when approaching the Sun. Near perihelion, from the comet’s nucleus, under the influence of solar heat and corpuscular flows, “evaporation” (sublimation) of frozen gases occurs and a luminous tail of the comet is formed, sometimes more than one. It consists of rarefied gases and small solid particles and is directed in the direction opposite to the Sun. The length of the tails reaches hundreds of millions of kilometers. The Earth has fallen into the tails of comets more than once, for example in 1910. This then caused great concern among people, although falling into comet tails does not pose any danger to the Earth: they are so rarefied that the admixture of poisonous gases contained in comet tails (methane, cyan), is imperceptible in the atmosphere.

Among periodic comets, the most interesting is Halley's comet, named after the English astronomer who discovered it in 1682 and calculated its orbital period (about 76 years). It was in its tail that the Earth found itself in 1910. It last appeared in the sky in April 1986, passing at a distance of 62 million km from Earth. Careful studies of the comet using spacecraft showed that the icy core of the comet is a monolithic body of irregular shape measuring about 15x7 km, around which a giant hydrogen corona with a diameter of 10 million km was discovered.

Comets are short-lived celestial bodies, since as they approach the Sun they gradually “melt” due to the intense outflow of gases or break up into a swarm of meteors. The meteoric material is subsequently more or less evenly distributed throughout the entire orbit of the parent comet. In this regard, the history of the periodic (about 7 years) comet Bijela, discovered in 1826, is interesting. Twice after its discovery, astronomers observed its appearance, and the third time, in 1846, they managed to record its division into two parts, which, on subsequent returns They were moving further and further away from each other. Then the meteoric material of the comet stretched across the entire orbit, during which the Earth crossed an abundant “rain” of meteors.

There is no precise evidence that the Earth has ever collided with a comet nucleus. No more than five comets penetrate into Earth's orbit each year. However, there is a version that the famous Tunguska “meteorite”, which fell in 1908 in the basin of the Podkamennaya Tunguska River, near the village of Vanavara, is a small (about 30 m) fragment of the nucleus of comet Encke, which exploded as a result of thermal heating in the atmosphere, and the “ice” " and solid impurities "evaporated". At the same time, the explosive air wave felled a forest over an area within a radius of 30 km.

In 1994, scientists observed the fall of Comet Shoemaker-Levy onto Jupiter. At the same time, it broke up into dozens of fragments 3–4 km in diameter, which flew one after another at an enormous speed - about 70 km/s, exploded in the atmosphere and evaporated. The explosions created a gigantic hot cloud 20 thousand km in size and with a temperature of 30,000 °C. The fall of such a comet to Earth would end in a cosmic catastrophe.

It is believed that the “comet cloud” surrounding the Sun formed along with the Solar System. Therefore, by studying the material of comets, scientists obtain information about the primary material from which planets and satellites were formed. In addition, assumptions have emerged about the “participation” of comets in the origin of life on Earth, since radio spectroscopic methods have proven the presence of complex organic compounds (formaldehyde, cyanoacetylene, etc.) in comets and meteorites.

Meteors, usually called “shooting stars”, are tiny (mg) solid particles that fly into the atmosphere at speeds of up to 50 - 60 km/s, heat up due to friction with the air to several thousand degrees Celsius, ionize gas molecules, causing them to emit light, and evaporate at an altitude of 80–100 km above the earth's surface. Sometimes a large and extremely bright fireball appears in the sky, which can break apart and even explode during flight. Such a meteor is called fireball. A similar fireball exploded on September 25, 2002 in the Irkutsk region, between the villages of Mama and Bodaibo. In the sky, both single meteors appearing randomly in the sky, and groups of meteors in the form of meteor showers, within which particles move parallel to each other, although in perspective it seems that they are scattering from one point in the sky, called radiant. Meteor showers are named by the constellations in which their radiants are located. The Earth crosses the orbit of the Perseids around August 12, the Orionids - October 20, the Leonids - November 18, etc. Meteor showers move along the orbits of those asteroids or comets, as a result of the disintegration of which they are formed. The orbits of meteor showers are carefully studied for the safety of spacecraft and vehicles.

Meteorites(from Greek meteora - celestial phenomena) are large meteoroids that fall to Earth. Every year, about two thousand meteorites with a total mass of about 20 tons fall onto the earth's surface. They are fragments of a rounded angular shape, usually covered with a thin black melting crust with numerous cells from the drilling action of air jets. According to their structure, they are of three classes: iron, consisting mainly of nickel iron, stone, which contain predominantly silicate minerals, and iron-stone, consisting of a mixture of these substances. Among the stony ones, there are two groups: chondrites (granular meteorites) and achondrites (earthy meteorites). Stony meteorites predominate (Fig. 3). Physico-chemical analysis of meteorites indicates that they consist of chemical elements and their isotopes known on Earth, which confirms the unity of matter in the Universe.

Rice. 3. a – relative frequency of meteorite falls of different classes (according to J. Boud); b – mineral composition of a typical chondrite (according to V. E. Khain)

The largest Goba meteorite, measuring 2.75x2.43 m and weighing 59 tons, was found in southwest Africa; it is iron. The Sikhote-Alin meteorite (fell in 1947) split into thousands of pieces in the air and fell to Earth as “iron rain.” The total weight of the collected fragments is about 23 tons, they created 24 impact craters ranging from 8 to 26 m in diameter. The Kaaba meteorite (“Black Stone”) is kept in the Mecca mosque in Saudi Arabia and serves as an object of worship for Muslims. Many meteorites have been discovered in Antarctica, and they are also found in the sediments of the floor of the World Ocean.

At the dawn of the Earth's existence, when there was still a lot of unused material in the solar system, and the Earth's atmosphere - protection from meteorites - was still very thin, the number of meteorites bombarding the Earth was enormous and its surface resembled the face of the Moon. Over time, most of the craters were destroyed by tectonic and exogenous processes, but many of them were still preserved in the form of ring-shaped geological structures called astroblemes(“star scars”). They are especially visible from space. They reach tens of kilometers in diameter. The study of meteorites allows us to judge the structure and properties of celestial bodies and supplements our information about the internal structure of the Earth.

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