Meteorites asteroids. Have you been interested? The ancient terrestrial craters arising, undoubtedly, from the fall of meteorites, were named astroborals, which in the ancient Greek means "star wounds". Astrolers are of age up to two billion years, and therefore an hour
Pugueva Olga and Chernyshova Dina
Astronomy presentation on the topic "Asteroids, comets, meteorites and meteors."
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Performed: Pugueva Olga and Chernyshova Dina Teacher: Malysheva V.I. MKOU "SOSH №1 PR. Warm »Asteroids, comets, meteorites and meteors
Asteroids differ greatly in size, from several hundred kilometers in diameter to the breed just a few tens of meters. Some of the largest are spherical and similar to miniature planets. However, the overwhelming majority are much less and have an irregular form. Physical composition Asteroids is changing and in many cases is understood too little. Some asteroids are solid particles of rocks with a smaller or large metal content, while others are formed from a breed formed by gravity.
Asteroids at the end of the XVIII century German astronomers Titius and baud independently of each other noted the pattern in a number of numbers expressing the average distances of the planets from the Sun. The fifth member of this row did not correspond to any planet. On January 1, 1801, the Italian astronomer Giuseppe Piazzi accidentally opened the star, direct climbing and the declination of which was noticeably changed during the observation day. Gauss calculated the orbit of this astronomical object and it became clear that the planet was opened between Mars and Jupiter. She was called Ceres in honor of the ancient Roman goddess fertility. In 1802, the German doctor Olbers, who fond of astronomy, opened a new planet near Ceres, which was called Pallada. In 1804, Juno was opened, in 1807 - Vesta. Herschel offered to call small planet asteroids. The asteroid in Greater means "star-shaped". In 1804, Olbras expressed the famous hypothesis about the rupture of the hypothetical planet Faeton between Mars and Jupiter and the formation of asteroids - her debris. The exact definition of the term "asteroid" is still not installed. Until 2006, asteroids were also called small planets.
One of the detected asteroids, Vesta, is visible to the naked eye, but only in some cases in luminous places with a very clear sky. Then came the discovery of other similar bodies, which have since been shown in the sky only as bright, star-like points that have a very small planetary disk or not at all. Some have months rotating around them, or they are in well-known co-orbital pairs and binary systems. Recently it was found that dwarf planets face the planets orbits, from Mercury to Neptune - with hundreds of trans-Neptune objects.
Starting from the end of the XIX century, the search for asteroids began to apply a photo. With long exposures, the images of asteroids due to their rapid movement are obtained in the form of a drop. Currently, more than 12,000 asteroids are known. At first they were called the names of the deities, then - names famous people. Until recently, the rule was observed: to call asteroids with female names, making an exception for asteroids with unusual orbits. Now the rules refused. Currently, the asteroid immediately after the opening is assigned a preliminary designation containing the year of discovery (for example, 1937 DA), and then if the asteroid orbit is defined reliably, the permanent number and name. And from the hypothesis of Olbers had to refuse. Detailed mathematical calculations show that asteroids occurred from crushing not one, but several bodies of large size.
Terminology The term asteroid is used to characterize a group of small celestial bodies rotating around the sun. This is the most famous term for small planetwhich is a term preferred by the International Astronomical Union. In other places, the term "planetoid" is preferred. As we used to, small bodies, rotating around the Sun, were classified as asteroids, comets or meteorites, any body less, say, 10 meters called meteorite. The main difference between asteroid and comets is its collar formed from ice particles due to solar radiation.
At the moment, hundreds of thousands of asteroids were detected in the solar system. As of September 6, 2011, there were 84,993,238 objects in the databases, 560,021 are defined orbits and the official number is assigned. 15615 Of these, they had officially approved names at this point. It is assumed that in the solar system can be from 1.1 to 1.9 million facilities having more than 1 km sizes. Most asteroids known at the moment are focused within the belt of asteroids located between the orbits of Mars and Jupiter. The largest asteroid in the solar system was considered a cerecher with sizes of approximately 975 × 909 km, however, from August 24, 2006, she received the status of a dwarf planet.
Several bodies began to be called twice, because they were originally classified as dwarf-dwarfs, but later commented on the actions. Some comets are rendered without a "ridge" and seem bright dots similar to asteroids. Subsequently, it is found that comets have more eccentric orbits than asteroids. In recent years, the discovery of trans-Neptune objects has complicated the situation. These objects fill out external borders Solar systemwhere ice remains solid, and cometary bodies do not cause too much cometic activity.
In 1975 Clark Chapman, David Morrison and Ben Cherler developed an asteroid classification system based on chroma performance, albedo and characteristics of the spectrum of reflected sunlight. Initially, this classification defined only three types of asteroids: Class C - carbon, 75% famous asteroids. Class S - silicate, 17% of famous asteroids. Class M - metal, most others. It should be borne in mind that the number of known asteroids attributed to any type is not necessarily true. Some types are quite complex to determine, and the type of a certain asteroid can be changed with more thorough studies. Classic asteroids
The most hidden of them are the objects of the Koiper belt, partially called "objects" to avoid the need to call them asteroids or comets. Current estimates find that the total number of asteroids with a diameter of more than 1 km in our solar system is from 1, 1 to 1, 9 million. Then the number of asteroids increases rapidly as the mass decreases. Various types of asteroids were discovered for the belt asteroids. The near-earth asteroids have orbits near the Earth orbits. Trojan asteroids gravitationally blocked by synchronization with the planet, occupying orbit behind it.
The danger of asteroids at the moment there is no asteroids that could significantly threaten the earth. The more heavier asteroid, the greater danger it represents, however, it is much easier to detect it in this case. The most dangerous at the moment is the asteroid of Apophis, with a diameter of about 300 meters, with a collision with which, in case of accurate hit, can be destroyed by a large city, but no threat of humanity in general is not boring. Representing global danger can asteroids are more than 10 km in diameter. All asteroids of this size are known to astronomers and are in orbits that cannot lead to a collision with the Earth.
Most Trojans are associated with Jupiter, but those who revolve around Mars or Neptune were discovered. Watching the naked an asteroid eye. Although he managed to identify tens of thousands of asteroids, they are almost impossible to notice with the naked eye, being too small. Asteroid 4 vest is an exception, being the only observed without optical devices, although its brightness is not too large. The asteroid shows the night sky, as well as a less bright star. The best way to find asteroids with binoculars or telescopes is to watch the stellar sky for several nights in a row and detect moving light objects relative to a fixed background.
Comets are beyond big planets And the asteroids around the sun moving comets. Comets - the most extended objects of the solar system. The word "comet" translated from Greek means "hairy", "long-haired". The emergence of most comet is unpredictable. People paid attention to them from time immemorial. It is impossible not to notice the spectacle in the sky so rare, and therefore, terrifying, more than any eclipse, when the misty luminaries can be seen in the sky, sometimes so bright that it can sparkle through the clouds (1577 years old), edemared even the moon. And from the bowels of the uninvited heavenly guest, huge tails are broken down ... Aristotle in the IV century BC. e. Explained the phenomenon of comet as follows: Easy, warm, "dry pneuma" (gases of the Earth) rises to the borders of the atmosphere, enters the sphere of heavenly fire and flammifies - "Tailed stars" are formed. Aristotle argued that comets cause severe storms, drought. His ideas were generally accepted for two millennia. In the Middle Ages, the comet was considered precursors of wars and epidemics. So the invasion of Normanov in South England in 1066 was associated with the appearance of comet Gallei in the sky. With the advent of the comet in the sky, Konstantinople was associated with the fall in 1456.
Humanity knows them for more than 200 years, but they were considered inappropriate products in the solar system. Today it is known that asteroids are an important key to understanding the formation of the solar system, and therefore astronomers are very interested in them. The first asteroid was discovered exclusively by Juseppe Piazzi, director astronomical observatory in Palermo, Sicily. His colleague Karl Friedrich Gauss uses these observations to determine their exact distance to the Earth.
His calculations were positioned by new astronomy between Mars and Jupiter. Piazzi calls them cerebral, named by the Greek Divine, which gives a sow from the ground and the first spring spring. It also includes other celestial bodies that do not fall into any of these categories, but despite this, they are very numerous: these are asteroids, meteors, meteors and comets. Sometimes these terms are mixed with each other or are used as synonyms: they actually identify well-defined celestial objects other than each other.
Comets open annually. On average, they are opened about 20 per year. Available observations of about 50 comets, and in the entire history of mankind, about two thousand appearances of comet observed. The orbits of the majority comet are strongly elongated ellipses. In 1702, Edmund Galli proved that comets 1531, 1607 and 1682 have the same orbit. It turns out comets come back! The period of circulation around the Sun of the Galeu Comet is 76 years.
Asteroids are small stony or metal bodies, often spherical, rotating around the sun. This is rather due to their small size than with their distance, which can be calculated by the method. Asteroids are present in different parts of the solar system, but are concentrated in the region between 1. 7 and 4 from the Sun, between the orbit of Mars and Jupiter, which is called the main asteroid heading. This bar takes the space between two planets, which is much wider than any other pair of planets in the solar system: on average, each planet has a distance from the sun in about 1, 3-2 times lower, but in the case of Mars and Jupiter, this value is about 3.
Comets arriving from cosmos depth look like foggy objects that stretch the tail, sometimes reaching several million kilometers. The comet core is a body of solid particles and ice, shrouded in a foggy shell, which is called a room. The kernel with a diameter of several kilometers can have around him in 80 thousand km in diameter. Solar beam streams knock out gas particles from the coma and discard them back, pulling into a long smoky tail, which moves behind it in space. Brightness comets very much depends on their distance to the sun. Of all the comet only a very small part approaches the Sun and the Earth so that they can be seen with the naked eye. The most visible ones are sometimes called "large (great) comets."
Astronomers who first observed the main asteroids, actually searched for a potential planet between the Martian or Jewish orbit, which could justify this large distance apparently "empty". It is believed that these asteroids could not be formed on the planet, probably because of the lot of gravity imposed by Jupiter, which made it difficult to build.
Among the most studied asteroids, we quote the go, in which there is also a small satellite, which is around, called dactyl. In addition to the main group, another important group is asteroid trojans that share orbit with Jupiter, and everyone has the names of such heroes as Achilles and Patrole.
The complex of comets is usually comets consist of a kernel and the surrounding light foggy shell (coma) consisting of gases and dust. W. bright Comet With the approach to the Sun, the "tail" is formed - a weak luminous band, which, as a result of light pressure and the operation of the solar wind, is most often directed in the opposite side of our luminaries. Tails heavenly Strangers. Comet is varied in length and shape. Some comets are drawn through all the sky. For example, the tail of the comet that appeared in 1944 was 20 million km long. And the C / 1680 V1 comet had a tail stretching for 240 million km. Cases of the tail of the tail from the comet were also recorded (C / 2007 N3 (Lulin)). The tails comet do not have sharp outlines and are practically transparent - the stars are clearly visible through them, because they are formed from an extremely rescued substance (its density is much less than the gas density released from the lighter). The composition is varied: gas or the smallest dust, or the mixture of both. The composition of most dusting is similar to the asteroid material of the solar system, which turned out as a result of the study of the comet 81p / Wilda spacecraft "Stardast". In essence, this is "visible nothing": a person can observe the tails of comets only because gas and dust are glowing. In this case, the gauge is associated with its ionization of ultraviolet rays and flows of particles emitted from the solar surface, and the dust simply dispels the sunlight.
Placing the main strip of asteroids and asteroid trojans. As a result of strikes, some of these asteroids can also exit their conventional orbits and approach the planets attracted by the gravitational power of the latter. Fortunately, larger objects often do not fall on our planet, which is somewhat bombarded by a number of small objects, including the size of the sand. They are destroyed due to a strike with "almost burned" due to friction with air: the visible result is a wonderful light that takes the name of the meteor.
In general language meteors are also called "Falling Stars", but we know that this is not the stars. In some periods of the year, many meteors are concentrated in the same sky, causing a meteorite swarm. When, on the other hand, the mass of the object turns out to be quite large to "survive" partially when a collision with an atmosphere, a fragment that reaches the surface of the Earth takes the name of the meteorite. Meteorites are also common to other planets and satellites, the surface of which, as a rule, create craters as a result of the strike, which can be seen on the outer crust of the Moon and Mercury, the celestial bodies without the atmosphere and, therefore, are more exposed to meteorites.
Comet Halley Exhaustive understanding of them Astronomers received thanks to successful "visits" in 1986 to the comet of Gallei spacecraft "Vega-1" and "Vega-2" and the European "Jotto". Numerous devices installed on these devices were transferred to the land of the nucleus of comet and a variety of information about its shell. It turned out that the core of Komet Gallei consists mainly of ordinary ice (with small inclusions of carbon dioxide and methane ice), as well as dust particles. It is they who form a comet shell, and with the approach of it to the Sun, some of them are under pressure from sunlight and solar wind - goes into the tail. The size of the kernel of the komet Halley, how to correctly calculated scientists, are equal to several kilometers: 14 - in length, 7.5 - in the transverse direction. The Komet Gallet's core has an irregular shape and revolves around the axis, which, as the German astronomer Friedrich Bessel (1784-1846) prevented (1784-1846), almost rebuilt the plane of the comet orbit plane. The period of rotation turned out to be 53 hours - which again agreed well with the calculations of astronomers.
In addition to the orbit of Neptune, there are other objects of alternating size and shapes, called TransNetunians, such as planets of Pluto and Eris. These two areas are part of the space that comes from small celestial bodies consisting of ice, water and gas, such as carbon dioxide, methane and ammonia, as well as powders and solid fragments, comets.
Some comets have parabolic or hyperbolic pathways, so they are not considered periodic. On the other hand, some of them periodically intersect the solar system with very eccentric elliptic orbits. I have a very long revolutionary period, so in the memory of a person you can not forget about two consecutive steps, while others have revolutionary periods of computability, and they can even be seen several times in a person's life. Just approaching the Sun becomes visible from the ground: an increase in temperature causes one of the frozen gases that make them up.
Comets and earth mass comets are insignificant - about billion times less than the mass of the Earth, and the density of the substance from their tails is almost equal to zero. Therefore, "Heavenly Guests" do not affect the planets of the solar system. In May 1910, the Earth, for example, passed through the tail of the comet of Gallei, but there was no change in the movement of our planet. On the other hand, a collision of a major comet with a planet can cause large-scale consequences in the atmosphere and the magnetosphere of the planet. A good and fairly qualitatively studied example of such a collision was the collision of fragments of the comet of Soviet meters-Levi 9 with Jupiter in July 1994
They form their hair, a kind of hail surrounding the core of the comet. The queue that characterizes comets consists of sublimated gases that are ionized and suspended by the solar wind. Therefore, the tail always turns in the direction of the Sun, and the comet "moves" to the Sun with a tail, so to speak, behind and leaves the tail ahead.
Among comet in a short revolutionary period, let's remember famous comet Gallea, which passes near the ground every 76 years. His name comes from English Astronoma Edmund Halley, who systematically studied it, waiting for the transition. It is believed that comets that periodically cross the solar system occur from the Kuiper group, while others in the deort cloud.
Meteors and meteorites Meteorite - the body of cosmic origin, falling on the surface of a large celestial object. Most of the meteorites found have weight from several grams to several kilograms. The largest meteorites found - Goba (whose weight, according to estimates, was about 60 tons). It is believed that 5-6 tons of meteorites fall on Earth, or 2 thousand tons per year.
In any case, the comet suggests their characteristic view of her hair and tail right near the sun, which "dresses", and then again becomes dark in the farthest places. In their passing near the Sun, comets are depleted both sublimation of gases that produce them and loss of solid particles that are attracted to the solar mass. Comets with relatively short revolutionary periods and, therefore, with the "frequent" passages near the Sun, the exhaustion of each passing, becoming less noticeable until they disappear, "the sun eaten".
Space body Before entering the atmosphere of the Earth is called a meteor body and is classified in astronomical features. For example, it can be cosmic dust, meteoroid, asteroid, their fragments, or other meteoric bodies. Flying through the atmosphere of the Earth and leaving a bright glowing trail in it, regardless of whether it will fly upper layers The atmosphere and will go back to the outer space, whether he burns in the atmosphere or falls to the ground, may be called either a meteor or a car. Meteors are considered to be the bodies not brighter than the 4th star magnitude, but by bollians - brighter than the 4th star magnitude, or the bodies that are distinguishable angular sizes.
Classification of Stone Chondriti Cultural Chondrites Common Chondrites Enstatite Chondrites Achondrites Iron-Stone Pallasites Mesosiderites Iron
Most often there are stone meteorites (92.8% of falls). The overwhelming majority of stone meteorites (92.3% of stone, 85.7% of the total number of falls) - Chondriti. Chondrites are called, since they contain chondra - spherical or elliptic formations of predominantly silicate composition. Most Hondron has a size no more than 1 mm in diameter, but some can reach several millimeters. Chondra is in a chip or fine-crystalline matrix, and often the matrix differs from Hondr not so much in composition, as in the crystalline structure. The composition of chondrites almost completely repeats chemical composition Sun, with the exception of lung gases, such as hydrogen and helium. Therefore, it is believed that chondrites were formed directly from the protoplanetic cloud surrounding the sun, by condensation of the substance and accretion of dust with intermediate heating.
Ahondriti make up 7.3% of stone meteorites. These are fragments of protoplanetary bodies that have undergone melting and differentiation in composition (on metals and silicates). Iron meteorites consist of iron-nickel alloy. They make up 5.7% of drops. Iron-silicate meteorites have an intermediate composition between stone and iron meteorites. They are relatively rare (1.5% drops).
Acondrites, iron and iron-silicate meteorites refer to differentiated meteorites. They presumably consist of a substance that has passed the differentiation in the composition of asteroids or other planetary bodies. It used to be that all differentiated meteorites were formed as a result of a gap of one or more large bodies, such as the planet of the phaseth. However, the analysis of the composition of different meteorites showed that with a greater probability they were formed from fragments of many major asteroids.
In place of falling a large meteorite, a crater (astroble) may form. One of the most famous crater in the world is Arizona. It is assumed that the greatest meteorite crater on Earth is Wilx Earth Crater (diameter of about 500 km). Earth and meteorites
The Tungus phenomenon (at the moment it is unclear exactly the meteoric origin of the Tungusian phenomenon. For details, see the article. Tunguska meteorite). Fell on June 30, 1908 in the river basin Podcaman Tunguska in Siberia. The total energy is estimated at 15.40 Megaton Ttrotil Equivalent. Tsarevsky meteorite (meteor rain). Fallen on December 6, 1922 near the village of Tsarev Volgograd region. This is a stone meteorite. The total mass of the collected fragments of 1.6 tons on an area of \u200b\u200babout 15 square meters. km. The weight of the largest fallen fragment was 284 kg. Sikhote-Alin meteorite (the total mass of fragments of 30 tons, energy is estimated at 20 kiloton). It was an iron meteorite. Fell in the Ussuri taiga on February 12, 1947, the Vitimi Car. Fell in the area of \u200b\u200bMom and the Vitimsky Mama-Chui district of the Irkutsk region on the night of September 24-25, 2002. The event had a large public resonance, although the total energy of the meteorite explosion, apparently, is relatively small (200 tons of trotyl equivalent, with an initial energy of 2.3 kilotons), the maximum initial mass (before combustion in the atmosphere) 160 tons, and the final mass of the order fragments Multiple hundred kilograms.
In the fall of large meteorites, large traces remain on earth. And when falling on the planet craters of even larger sizes: they are clearly visible on them.
Three meteor flows - Leonides, Andromedids and Draconides - were showed very sharp outbreaks of activity in historical times, and in the case of Andromedd, it was directly related to the destruction of the biely comet, which in 1845 he was revealed and in the next appearance, in 1852, was visible as two Weak comets, separated by the distance over 1.5 million km. Draconides were associated with another comet - Jacobini - Zinner. If the comet's orbit crosses the Earth orbit, then annually when the Earth falls into the intersection point, meteoric rains are observed, increasing with a simultaneous approach to this point of the Earth and comet's residues. If the amplification is not observed, it means that the substance of the comet is more or less evenly dispersed in orbit - the comet completely ceased to exist as heavenly body.
Asteroids. Meteorites. Meteors.
Asteroid
Asteroid is a small planet-like celestial body of the solar system, moving in orbit around the sun. Asteroids, known as small planets, are significantly inferior in size by planets.
Definitions.
The term asteroid (from Dr.-Greek.- "Such a star") was introduced by William Gershel based on the fact that these objects when observing the telescope looked like points of stars - unlike planets, which when observing the telescope looks with discs. The exact definition of the term "asteroid" is still not installed. The term "small planet" (or "planetoid") is not suitable for determining asteroids, as it also points to the location of the object in the solar system. However, not all asteroids are small planets.
One way to classify asteroids is the definition of size. The current classification determines asteroids as objects with a diameter of more than 50 m, separating them from meteoric telwhich look like large stones, or may be even less. The classification relies on the statement that asteroids can survive at the entrance to the Earth's atmosphere and reach its surface, while meteors are usually completely burned in the atmosphere.
As a result, the asteroid can be defined as an object of the solar system consisting of solid materials, which in size more meteor.
Asteroids in the Solar System
At the moment, tens of thousands of asteroids were found in the solar system. As of September 26, 2006, there were 3,85083 facilities in the databases, 164612 are defined orbits and the official number is assigned. 14077 Of these, they had officially approved names at this moment. It is assumed that in the solar system can be from 1.1 to 1.9 million facilities having more than 1 km sizes. Most asteroids known at the moment are focused within the belt of asteroids located between the orbits of Mars and Jupiter.
The largest asteroid in the solar system was considered a cerecher with sizes of approximately 975 × 909 km, however, from August 24, 2006, she received the status of a dwarf planet. The other two of the largest asteroid 2 pallades and 4 Vesta have a diameter of ~ 500 km. 4 Vesta is the only object of the belt of asteroids, which can be observed with a naked eye. Asteroids moving in other orbits can also be observed during the passage near the Earth (for example, 99942 Apophis).
The total mass of all the main belt asteroids is estimated at 3.0-3.6 × 1021 kg, which is only about 4% of the mass of the moon. Ceres weight - 0.95 × 1021 kg, that is, about 32% of the total, and together with the three largest asteroids 4 wester (9%), 2 pallades (7%), 10 gigay (3%) - 51%, that is, the absolute majority Asteroids have an insignificant mass.
Study asteroids
The study of asteroids began after discovery in 1781 William Germel Planet Uranus. Its average heliocentric distance turned out to be a corresponding Titsius-Bode rule.
At the end of the XVIII century, Franz Xaver (Franz Xaver Von Zach) organized a group that included 24 astronomers. Since 1789, this group was engaged in the search for the planet, which, according to the rule of Tizius-Bode, was supposed to be 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 field of zodiac constellations at a certain point. In the subsequent nights, the coordinates were checked, and objects were distinguished that shifted to a greater distance. The estimated displacement of the desired planet should have been about 30 angular seconds per hour, which should have been easily noticed.
Ironically, the first asteroid, 1 ceres, was discovered by the Italian Piazzi, who did not participate in this project, by chance, in 1801, on the first night century. Three others - 2 pallades, 3 Junon and 4 Vesta were found in the next few years - the last, Vesta, in 1807. After 8 years of fruitless search, most astronomers decided that there is nothing more, and there was nothing else, and stopped research.
However, Karl Ludwig Henke showed perseverance, and in 1830 resumed the search for new asteroids. Five years later, he discovered an astray, the first new asteroid for 38 years. He also discovered Gebu less than two years. After that, other astronomers joined the search, and further was found at least one new asteroid per year (with the exception of 1945).
In 1891, Max Wolf first used to search asteroids, the method of astrophotography, in which there were short light lines in photographs with a long period of exposure of the asteroids. This method significantly increased the number of detection compared to previously used visual observation methods: Wolf alone found 248 asteroids, starting with 323 browns, whereas it was found to be discovered more than 300. Now, a century later, only a few thousand asteroids identified, numbered and Replaced. It is known about them much more, but scientists are not very worried about their study, calling asteroids "Space Lying" ("Vermin of the Skies").
Naming asteroids
First, the asteroids gave the names of the heroes of Roman and Greek mythology, later the openers received the right to call him anything, for example, by their name. Initially, asteroids were predominantly female names, male names received only asteroids having unusual orbits (for example, Icar, approaching the Sun closer than Mercury). Later and this rule stopped observed.
Not any asteroid may receive a name, but only one orbit of which is more or less reliably calculated. There were cases when the asteroid received a name after decades after the opening. As long as the orbit is calculated, the asteroid is given a sequence number reflecting the date of its discovery, for example, 1950 DA. The numbers denote the year, the first letter - the number of the crescent in the year, in which the asteroid was opened (in the example given the second half of February). The second letter denotes the sequence number of the asteroid in the specified crescent, in our example asteroid was opened first. Since the crescents 24, and the English letters - 26, there are no two letters in the designation: i (due to the similarity with unit) and Z. If the number of asteroids opened for the crescent will exceed 24, they return to the beginning of the alphabet, attributing the second letter 2 letter 2, with the next return - 3, etc.
After receiving the name, the official naming of the asteroid consists of among the (ordinal number) and the names - 1 ceres, 8 flora, etc.
Asteroid belt
The orbits of the majority of numbered small planets (98%) are located between the orbits of the planets of Mars and Jupiter. Their average distances from the Sun are from 2.2 to 3.6 AE. They form the so-called main belt of asteroids. All small planets, as big, are moving in the forward direction. The periods of their appeal around the Sun make up 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 small planets are noticeably elongated. Eccentricity rarely exceed 0.4, but, for example, at the asteroid 2212 hefesta it is 0.8. Most orbits are located close to the plane of the ecliptic, i.e. To the plane of the orbit of the Earth. The slopes usually constitute several degrees, but there are exceptions. Thus, the orbit of Ceres has a shifting of 35 °, great inclination is also known.
Perhaps we are most important to know asteroids, the orbits of which are close to the orbit of our planet. Typically distinguish three families to the ground asteroids. They are named by the name of typical representatives - Small Planets: 1221 Amur, 1862 Apollo, 2962 Athon. The Amur family includes asteroids whose orbits in the perichelia are almost concerned with the Earth's orbits. Apollors crosses the Earth orbit from the outside, their overheaturation is less than 1 AE. "Athintians" have orbits with a large half-axis less ground and crossed the earth orbit from the inside. Representatives of all these families can meet with Earth. As for close passages, they often happen.
For example, Amur asteroid at the time of discovery was 16.5 million kilometers from Earth, 2101 Adonis approached 1.5 million kilometers, 2340 Hathor - by 1.2 million kilometers. Astronomers of many observatories observed passage by the Earth asteroid 4179 Tautatis. On December 8, 1992, he was from us at a distance of 3.6 million kilometers.
The main amount of asteroids is concentrated in the main belt, but there is important exceptions. Long before the opening of the first asteroid French mathematician Joseph Louis Lagrang studied the so-called task of three bodies, i.e. He studied how three bodies are moving under the action of the forces of gravity. The task is very complex and generally not solved until now. However, Lagrange managed to find that in the system of three gravel bodies (the sun - the planet - a small body) there are five points, where the movement of a small body turns out to be stable. Two of these points are in the orbit of the planet, forming the equilateral triangles with it and the sun.
Many years later, already in the XX century, theoretical constructions were embodied in reality. Near the Lagrangian Points in the orbit of Jupiter, about two dozen asteroids were opened, which were given to the names of the heroes of the Trojan War. Asteroids - "Greeks" (Achill, Ajax, Odyssey, etc.) Ahead of Jupiter at 60 °, "Trojans" follow at the same distance from the back. According to estimates, the number of asteroids near Lagrange points can reach several hundred.
Dimensions and material composition
To find out the size of a astronomical object (if the distance to it is known), it is necessary to measure the angle under which it is visible from the ground. However, it is not by chance that asteroids are called small planets. Even in large telescopes with excellent atmospheric conditions, applying very complex, labor-intensive techniques, it is possible to obtain quite fuzzy outlines of discs of only the largest asteroids. Much more efficiently turned out to be a photometric method. There are very accurate devices that measure glitter, i.e. Starry magnitude of heavenly shining. In addition, the illumination created by the Sun on the asteroid is well known. All other things being equal, the brilliance of the asteroid is determined by the area of \u200b\u200bits disk. It is necessary, however, to know what kind of light reflects this surface. This reflectivity is called albedo. The methods of its determination on the polarization of the light of asteroids are developed, as well as on 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 dimensions of the largest asteroids were obtained.
It is believed that asteroids with diameters are more than 200 km three dozen. Almost all of them are probably known. Small planets with diameters from 80 to 200 km, probably about 800. With a decrease in sizes, the number of asteroids increases rapidly. Photometric studies have shown that asteroids differ greatly according to the degree of blackness of the substance that is founding their surface. 52 Europe, in particular, has albedo 0.03. This corresponds to a dark substance, in color similar to Say. Similar dark asteroids are conventionally called coaling (class C). The asteroids of another class are conditionally referred to as stone (s), as they seem to resemble the deep rock rocks. Albedo S-asteroids is significantly higher. For example, in 44 bottoms it reaches 0.38. This is the brightest asteroid. The study of the reflection spectra and polarimetry made it possible to allocate another class - metal, or M-asteroids. Probably, there are metal outputs on their surface, such as nickel gland, like some meteorites.
With the help of very sensitive photometers, periodic changes in the brightness of asteroids were investigated. In the form of the gloss curve, you can judge the period of rotation of the asteroid and the position of the rotation axis. Periods are most different - from several hours to hundreds of hours. The study of the shine curve allows you to make certain conclusions about the form of asteroids. Most of them have an incorrect, debris form. Only the biggest approach to the ball.
The nature of the change in the shine of some asteroids gives reason to assume that they have satellites. Some of the small planets may be close to double systems or even rolling through each other's bodies.
But reliable information about asteroids can only give observations from a close distance - with spacecraft. Such experience is already available. On October 29, 1991, the American Space Actuate "Galileo" handed over to Earth an image of an asteroid 951 Gaspra. The snapshot is made from the distance of 16 thousand kilometers. It is clearly visible to the angular smoothed form of asteroid and its conductor surface. You can confidently determine the size: 12x16 km.
For a long time, asteroids were not known, the orbits of which were entirely under the limits of the orbit of Jupiter. But in 1977 it was possible to detect such a small planet - it is 2060 chiron. The observations showed that his perigelius (the orbit closest to the sun) lies inside the orbit of Saturn, and the aphelius (the point of the greatest removal) is almost at the orbit of uranium, on distant, cold and dark outlets of the planetary system. The distance to Hiron to the perihelion 8,51 AE, and in Aflia - 18.9 AE. More donated asteroids were found. It is assumed that they form the second, the external belt of asteroids (the belt belt).
The brightest asteroid
Asteroid, which seems the most bright from the Earth - Vesta (4). When Vesta is at the lowest distance from the ground, its brightness reaches a star value of 6.5. With a very dark, Vesta can be detected even with a naked eye (this is the only asteroid that can be selected in generally with the naked eye). The next brightness is the largest asteroid of Cerer, but its brightness never exceeds the stellar value of 7.3. Although Vesta size is three fifths from Ceres, it has a much greater reflectivity. Vesta reflects about 25% of sunlight falling on it, while Ceres are just 5%. Vesta seems like light volcanic rocks that have a high reflectivity. Asteroids with such reflective ability belong to a separate class, known as the type E (the designation of the class comes from the name of the mineral enstatite). Such asteroids are rare, and their reflective ability lies in the range from 30 to 40%. The brightest of them is NIS (44) - has a stellar value of 9.7, although its diameter is only 68 km.
METEORITE
Meteorite - a piece of extraterrestrial substance that fell on the surface of the Earth; Literally - "Stone from the sky."
Meteorites are the oldest of famous minerals (4.5 billion years), therefore, they must be preserved traces of processes accompanying the formation of the planets. While the samples of the lunar soil were not delivered to the Earth, meteorites remained the only samples of the extraterrestrial substance. Geologists, chemists, physics and metallurgists are collecting and studying meteorites for more than 200 years. From these studies, there was a science of meteorites. Although the first messages about the fall of meteorites have long appeared, scientists belonged to them very skeptical. A variety of facts forced them in the end, believe in the existence of meteorites. In 1800-1803, several well-known European chemists reported that the chemical composition of "meteor stones" from different places of the fall is similar, but differs from the composition of earthly rocks. Finally, when in 1803 in Egle (France), a terrible "Stone Rain" broke out, who suiced the land by fragments and witnessed by many excited eyewitnesses, the French Academy of Sciences was forced to agree that these were really "stones from the sky." It is now believed that meteorites are fragments of asteroids and comets.
Meteorites are divided into "fallen" and "found". If a person saw a meteorite fell through the atmosphere and then really discovered it on Earth (a rare event), then such a meteorite is called "fallen". If he was found randomly and identified, which is typically for iron meteorites, it is called "found". Meteorites give names by names where they were found. In some cases, not one, but a few Oskov. For example, after a meteor rain 1912 in Holbruck (pieces of Arizona) more than 20 thousand fragments were collected.
Fall of meteorites. As long as the meteorite has reached the Earth, it is called a meteoroid. Meteoroids flies into the atmosphere with speeds from 11 to 30 km / s. At an altitude of about 100 km due to friction about the air, the meteoroid begins to heat up; Its surface is split, and a layer of a few millimeters is melted and evaporates. At this time it can be seen as a bright meteor (see Meteor). The molten and evaporated substance is continuously demolished by the pressure of air - this is called ablation. Sometimes under the pressure of the air, the meteor is crushed into a variety of fragments. Passing through the atmosphere, it loses from 10 to 90% of the initial mass. Nevertheless, the internal part of the meteor usually remains cold, because it does not have time to warm up for those 10 s, which lasts fall. Overcoming air resistance, small meteorites at the moment of impact of the Earth significantly reduce the flight speed and deepen into the ground usually not more than a meter, and sometimes they just remain on the surface. Large meteorites are inhibited slightly and when hitting an explosion to form a crater, such as in Arizona or on the moon. The largest found meteorites found an Iron meteorite Goba (South Africa), whose weight is estimated at 60 tons. He was never shifted from the place where they found.
Every year several meteorites are selected immediately after their observed fall. In addition, old meteorites are increasingly discovered. In two places in the east pcs. New Mexico, where the wind constantly blows the soil, 90 meteorites were found. On the surface of evaporating glaciers in Antarctica, hundreds of meteorites were discovered. Recently fallen meteorites are covered with a glacited crust, which is darker inner. Meteorites are of great scientific interest; In most large natural-scientific museums and in many universities there are specialists in meteorites.
Meteorite, possibly coming from Mars. Detected in Antarctica in 1984. Types of meteorites. Meteorites are found from various substances. Some mainly consist of iron and nickel alloy containing up to 40% nickel. Among fallen meteorites Only 5.7% of iron, but in the collections their share is much larger, as they are slower to destroy the influence of water and wind, besides, they are easier to detect them in appearance. If you polish the slice of an iron meteorite and move slightly with acid, then it is often a crystalline pattern from intersecting bands formed by alloys with different nickel content on it. This drawing is called "Vidamanstetten Figures" in honor of A.vidmanshtetten (1754-1849), the first observed them in 1808.
Iron meteorite from Henbery (Australia) is a typical metallic type meteorite, many of which are rich in the compounds encountered in iron ores.
Stone meteorites are divided into two large groups: Chondritis and Achondrites. Chondrites are most often found, making up 84.8% of all fallen meteorites. They contain rounded grains of millimeter size - chondra; Some of the meteorites are almost entirely consisting of Hondr. In earthly breeds, the chondra was not found, but the size of the vitreous grains were found in the lunar soil. Chemists carefully studied them, since the chemical composition of Hondr probably represents the primary substance of the solar system. This standard composition is called "cosmic abundance of elements." In chondrites of a certain type containing up to 3% of carbon and 20% of water, stiguously searched for signs of biological substance, but none in these, nor in other meteorites did not find any signs of living organisms. Ahondrita is deprived of Honder and look like a lunar breed.
Meteorite-Ahondrith
Meteorite-Chondrite.
Parent bodies meteorites. The study of mineralogical, chemical and isotopic composition of meteorites showed that they are fragments of larger solar system objects. The maximum radius of these parent bodies is estimated at 200 km. About this size have the most large asteroids. The assessment is based on the cooling rate of the iron meteorite, in which two alloy with nickel forming the species of the shapes are obtained. Stone meteorites were probably knocked out from the surface of small planets, devoid of atmosphere and crates covered as the moon. Space radiation destroyed the surface of these meteorites as well as lunar stones. However, the chemical composition of meteorites and lunar samples is so different that it is completely obvious - meteorites arrived not from the moon. Scientists were able to photograph two meteorites in the process of falling and calculating their orbit's photographs: it turned out that these bodies came from the belt asteroids. Probably asteroids serve as the main sources of meteorites, although some of them can be particles of evaporated comets.
METEOR. The word "meteor" in Greek was used to describe various atmospheric phenomena, but now they denote the phenomena that occur when the atmosphere of solid particles from the space appears in the upper layers. In the narrow sense of the "meteor" is a luminous strip along the split particle highway. However, in everyday life, this word is often indicated by the particle itself, although it is called a meteoroid in a scientific. If part of the meteoroid reaches the surface, it is called a meteorite. Meteora people are called "falling stars." Very bright meteors are called carbillars; Sometimes this term denote only meteor events, accompanied by sound phenomena.
Frequency of appearance. The number of meteors that can see the observer for a certain period of time, not constantly. In good conditions, away from urban lights and in the absence of bright lunar light, the observer may notice 5-10 meteors per hour. Most meteors the glow continues around a second and looks weaker than the brightest stars. After midnight, meteors appear more often, since the observer at this time is located on the front of the orbital movement to the side of the Earth, which enters more particles. Each observer can see meteors within a radius of about 500 km around themselves. In total, one per day in the atmosphere of the Earth arise hundreds of millions of meteors. The total weight of the particles flying into the atmosphere is estimated in thousands of tons per day - an insignificant value compared with the mass of the earth itself. Measurements from spacecraft show that during the day there is also about 100 tons of dust particles, too small to cause the appearance of visible meteors.
Observation of meteors. Visual observations give many statistical data on meteors, but to accurately determine their brightness, height and flight speed requires special devices. Already near the century, astronomers use cameras for photographing meteor traces. The rotating flap (obturator) in front of the camera lens makes the meteor trail similar to a dotted line, which helps accurately determine the time intervals. Usually, using this flap is made from 5 to 60 exposures per second. If two observer, separated by the distance in tens of kilometers, at the same time photograph the same meteor, you can accurately determine the height of the particle's flight, the length of its trace and - at the time intervals - the flight speed.
Since the 1940s, astronomers are watching meteors with a radar. The cosmic particles themselves are too small to register them, but when flying in the atmosphere, they leave a plasma footprint, which reflects radio waves. Unlike the photo, the radar is effective not only at night, but also during the day and in cloud weather. The radar notices small meteoroids, inaccessible to the camera. The photographs are more accurately determined by the flight path, and the radar allows you to accurately measure the distance and speed.
Television equipment is used to observe meteors. Electronic optical converters allow you to register weak meteors. Cameras with CCD matrices are used. In 1992, when recording on a video camera of sports competitions, a bright car flew was recorded ending with a meteorite.
Speed \u200b\u200band height. The speed with which meteoroids flies into the atmosphere, is in the range from 11 to 72 km / s. The first value is the speed acquired by the body only by attraction of the Earth. (The same speed should be obtained by a spacecraft to escape from the gravitational field of the Earth.) The meteoroid, which arrived from the distant regions of the solar system, due to attraction to the Sun acquires a speed of 42 km / s near the earth orbit. Earth's orbital speed is about 30 km / s. If the meeting happens "in the forehead", then their relative speed is 72 km / s. Any particle that comes from interstellar space must have even more speed. The absence of so fast particles proves that all meteoroids are members of the solar system.
Bright meteor from the Perseid stream. The height on which the meteor begins to glow or marked the radar depends on the speed of the particle input. For quick meteoroids, this height may exceed 110 km, and completely particle collapses at an altitude of about 80 km. In slow meteoroids, this happens below, where there is more air density. Meteors comparable in shine with the brightest stars are formed by particles with a mass in tenth grams. Larger meteoroids are usually destroyed longer and reach small heights. They are essentially inhibited due to friction in the atmosphere. Rare particles fall below 40 km. If the meteoroid reaches a height of 10-30 km, then its speed becomes less than 5 km / s, and it can fall to the surface in the form of a meteorite.
Orbits. Knowing the speed of the meteoroid and the direction from which he flew to the ground, an astronomer can calculate his orbit before a collision. Earth and meteoroid are faced if their orbits intersect and they are simultaneously rendered at this intersection point. The orbits of meteoroids are both almost circular and extremely elliptic, leaving on planetary orbits.
If the meteoroid is approaching the ground slowly, it means that it moves around the Sun in the same direction as the Earth: counterclockwise, if you look at the North Pole of the orbit. Most of the orbits of meteoroids goes beyond the terrestrial orbit, and their plane is inclined to the ecliptic not very much. The drop in almost all meteorites is associated with meteoroids that had less than 25 km / s. Their orbits are completely underway inside the orbit of Jupiter. Most of the time these objects spend between the orbits of Jupiter and Mars, in the belt of small planets - asteroids. Therefore, it is believed that asteroids serve as a source of meteorites. Unfortunately, we can observe only those meteoroids that cross the Earth's orbit; Obviously, this group does not fully fully represent all the small bodies of the solar system.
Fast meteoroids, orbit are more elongated and stronger tilted to the ecliptic. If the meteoroid is pumped at a speed of more than 42 km / s, then it moves around the sun in the direction opposite to the direction of movement of the planets. The fact that many comets are moving in such orbits, indicates that these meteoroids are fragments of comets.
Meteor threads. On some days of the year, meteors appear much more often than usual. This phenomenon is called a meteoric flow when tens of thousands of meteors per hour are observed, creating an amazing phenomenon of "Star Rain" throughout the sky. If you trace the path of meteors in the sky, it will seem that they all fly out of one point called the flux radiant. This phenomenon of perspective, similar to converging near the horizon, indicates that all particles move along parallel trajectories.
Astronomers allocated several dozen meteoric streamsMany of which demonstrate annual activity with a duration of several hours to several weeks. Most of the flows are named by the name of the constellation, in which their radiant lies, for example, Perseys, which have a radiant in the constellation Perseus, Geminides - with a radiant in the twins.
Meteor flows are observed when the land crosses the path of the part of the particles formed during the destruction of the comet. Approaching the sun, the comet is heated by its rays and loses the substance. For a few centuries, under the action of gravitational perturbations from planets, these particles form a comet's elongated along the orbit. If the earth crosses this stream, we can annually observe Star rain, even if the comet itself is far from the ground. Since the particles are distributed along the orbits unevenly, the rain intensity can change from year to year. Old flows are so expanded that the Earth crosses them a few days. In the section, some streams rather resemble a tape than the cord.
The ability to observe the flow depends on the direction of the arrival of particles to the ground. If the radiant is high in the northern sky, then the stream is not visible from the southern hemisphere of the Earth (and vice versa). Meteors stream can be seen only if the radiant is above the horizon. If the radiant falls on the day sky, the meteors are not visible, but they can be driving a radar. Narrow streams under the influence of planets, especially Jupiter, can change their orbits. If at the same time they no longer intersect the earth orbit, then become unobservable.
The December stream of Geminides is associated with the remnants of a small planet or an inactive nucleus of an old comet. There is an indication that the Earth faces with other groups of meteoroids generated by asteroids, but these streams are very weak.
Charges. Meteors, which are brighter than the brightest planets, are often called carbillars. Sometimes there are bridged cars with a brightest moon and extremely rarely such that the brighter sun flashes. Charges arise from the largest meteoroids. Among them are many fragments of asteroids that are denser and stronger than fragments of cometary nuclei. But all the same most asteroid meteoroids are destroyed in dense layers of the atmosphere. Some of them fall on the surface in the form of meteorites. Due to the high brightness of the outbreak, the damasses seem much closer than in reality. Therefore, it is necessary to compare the observations of the barids from various places before organizing the search for meteorites. Astronomers appreciated that daily throughout the Earth about 12 of the barids ends with a drop in more than kilogram meteorites.
Physical processes. The destruction of the meteoroid in the atmosphere occurs by ablation, i.e. High-temperature cleavage of atoms from its surface under the action of flourishing air particles. The hot gas trail remains behind the meteoroid radiates light, but not as a result of chemical reactions, but due to recombination of atoms excited by blows. In the spectra of meteors, many bright emission lines are visible, among which iron, sodium, calcium, magnesium and silicon prevail. The lines of atmospheric nitrogen and oxygen are also visible. The chemical composition of meteoroids determined by the spectrum is consistent with the data on comets and asteroids, as well as about interplanetary dust, assembled in the upper layers of the atmosphere.
Many meteors, especially fast, leave a luminous trail, observed second or two, and sometimes - much longer. When large meteorites fell, the trace was observed for several minutes. The luminescence of oxygen atoms at altitudes OK. 100 km can explain the traces of the duration of no more than a second. More long traces arise due to the complex interaction of a meteoroid with atoms and atmospheric molecules. Dust particles along the trajectory of a car can form a bright mark, if the upper layers of the atmosphere, where they are scattered, illuminated by the Sun, when the observer is at the bottom of the deep twilight.
The speed of meteoroids is hypersonic. When the meteoroid reaches a relatively dense layer of the atmosphere, a powerful shock wave occurs, and strong sounds can be distributed for tens or more kilometers. These sounds resemble thunder rolls or a distant canonade. Due to the long distance, the sound comes for a minute or two later appearance of a car. A few decades of astronomers argued about the reality of anomalous sound, which some observers were heard directly at the time of the appearance of a car and described as a crack or whistle. Studies have shown that the cause of the sound is the perturbation of the electric field near the car, under the influence of which they publish the sounds close to the observer facilities - hair, fur, trees.
Meteoric danger. Large meteoroids can destroy spacecraft, and small dusts constantly draw their surface. The blow of even a small meteoroid can inform the satellite electrical charge, which means electronic systems. The risk in general is small, but still launching spacecraft sometimes postpone if a strong meteor flow is expected.
Bibliography
1 Simonenko A.N. Meteorites are fragments of asteroids. M., 1979.
2 hetman V.S. Sun grandchildren. M., 1989.