New interesting scientific information about comets. What is the difference between a comet and an asteroid
Cold objects, consisting of solid rocks (including metals) and ice, are part of the Solar System. These objects are asteroids, comets, meteoroids.
Comet
Comets are composed of a mixture of ice, frozen gas and dust. They travel around the Sun in very elongated orbits. As a comet approaches the Sun, ice and other volatile substances on its surface quickly evaporate, creating a stream of gas and dust. The solar wind and light pressure “blow away” the resulting gases with other substances away from the Sun. This is how the luminous tail of a comet is formed. The comet's tail can reach 10 million km.
Long-period comets with an orbital period of more than 200 years around the Sun come from regions further than the outer planets of the system, in the Oort cloud, which probably exists at a distance of almost a light year from the Sun, about a quarter of the way to our nearest star Proxima Centauri (distance it is 4.3 light years away, or 40 trillion km). It is believed that there are about a trillion comets in the Oort cloud. Short-period comets (periods of less than 200 years) come from the region of the outer planets - these are objects from the Kuiper belt located beyond the orbit of Neptune. Halley's Comet orbits the Sun every 76 years, making it the most... famous comet in history.
Asteroid
Most of the solar system's asteroids are concentrated in the belt between the orbits of Mars and Jupiter. Asteroids are, in all likelihood, part of protoplanetary matter - planetesimals, formed at the boundary of the hot and cold zones of the protoplanetary disk and preserved to this day. Carbon, metallic, silicate, etc. asteroids are known.
An asteroid may fall out of orbit under the influence of a gravitational field major planets or another asteroid. Such a stray asteroid could collide with a planet or satellite and fall to the surface as a meteorite. Sometimes this leads to destruction. Some scientists believe that about 65 million years ago a meteorite crashed into the Earth, which led to the extinction of the dinosaurs.
Cosmic dust, meteoroids - bodies larger than dust, but smaller than an asteroid, and asteroids themselves, which do not burn up, but crash into the Earth in the form of meteorites, fall to the Earth from space. Some of the meteorites are so large that they leave craters. The most famous place The Berringer impact crater in Arizona, USA is considered to be the site of a meteorite impact on Earth. This is the result of the fall of an iron meteorite weighing about 300 thousand tons, which collided with the Earth at a speed of 45-60 thousand km/h about 50,000 years ago.
On warm summer nights it is pleasant to walk under the starry sky, look at the wonderful constellations on it, and make wishes at the sight of a falling star. Or was it a comet passing by? Or maybe a meteorite? There are probably more astronomy experts among romantics and lovers than among planetarium visitors.
Mysterious space
Questions that constantly arise during contemplation require answers, and celestial mysteries require solutions and scientific explanations. For example, what is the difference between an asteroid and a meteorite? Not every schoolchild (or even adult) will be able to answer this question right away. But let's start in order.
Asteroids
To understand the difference between an asteroid and a meteorite, you need to define the concept of “asteroid”. This word from ancient Greek is translated as “star-like”, since these celestial bodies, when observed through a telescope, resemble stars rather than planets. Until 2006, asteroids were often called minor planets. Indeed, the movement of asteroids in general is no different from planetary movement, because it also occurs around the Sun. Asteroids differ from ordinary planets in their small size. For example, the largest asteroid, Ceres, is only 770 km across.
Where are these star-like space inhabitants? Most asteroids move along long-studied orbits in the space between Jupiter and Mars. But some small planets still cross the orbit of Mars (such as the asteroid Icarus) and other planets, and sometimes even come closer to the Sun than Mercury.
Meteorites
Unlike asteroids, meteorites are not inhabitants of space, but its messengers. Each earthling can see a meteorite with his own eyes and touch it with his own hands. A large number of them are kept in museums and private collections, but it must be said that meteorites look rather inconspicuous. Most of them are gray or brownish-black pieces of stone and iron.
So, we managed to figure out how an asteroid differs from a meteorite. But what can unite them? Meteorites are believed to be fragments of small asteroids. Stones flying in space collide with each other, and their fragments sometimes reach the surface of the Earth.
The most famous meteorite in Russia is the Tunguska meteorite, which fell in the remote taiga on June 30, 1908. In the recent past, namely in February 2013, attracted everyone's attention Chelyabinsk meteorite, whose numerous fragments were found in the area of Lake Chebarkul in the Chelyabinsk region.
Thanks to meteorites, peculiar guests from space, scientists, and with them all the inhabitants of the Earth, have an excellent opportunity to learn about the composition of celestial bodies and gain insight into the origins of the universe.
Meteora
The words “meteor” and “meteorite” come from the same Greek root, meaning “heavenly”. We know what a meteorite is, and how it differs from a meteor is not difficult to understand.
A meteor is not a specific celestial object, but an atmospheric phenomenon that looks like It occurs when fragments of comets and asteroids burn up in the Earth's atmosphere.
A meteor is a shooting star. It may appear to observers, fly back into outer space, or burn up in the Earth's atmosphere.
It is also not difficult to understand how meteors differ from asteroids and meteorites. The last two celestial objects are concretely tangible (even if theoretically in the case of an asteroid), and the meteor is a glow resulting from the combustion of cosmic fragments.
Comets
An equally wonderful celestial body that an earthly observer can admire is a comet. How do comets differ from asteroids and meteorites?
The word “comet” is also of ancient Greek origin and is literally translated as “hairy”, “shaggy”. Comets come from the outer solar system, and therefore have a different composition than asteroids that formed near the Sun.
Besides the difference in composition, there is a more obvious difference in the structure of these celestial bodies. When approaching the Sun, a comet, unlike an asteroid, exhibits a hazy coma shell and a tail consisting of gas and dust. As the comet heats up, its volatile substances are actively released and evaporated, turning it into a beautiful luminous celestial object.
In addition, asteroids move in orbits, and their movement in outer space resembles the smooth and measured movement of ordinary planets. Unlike asteroids, a comet is more extreme in its movements. Its orbit is highly elongated. The comet either approaches the Sun closely or moves away from it to a considerable distance.
A comet differs from a meteorite in that it is in motion. A meteorite is the result of a collision of a celestial body with the earth's surface.
Heavenly peace and earthly peace
It must be said that watching the night sky is doubly pleasant when its unearthly inhabitants are well known and understandable to you. What a pleasure it is to tell your interlocutor about the world of stars and unusual events in outer space!
And the point is not even in the question of how an asteroid differs from a meteorite, but in the awareness of the close connection and deep interaction between the earthly and cosmic worlds, which must be established as actively as the relationship between one person and another.
MINISTRY OF EDUCATION AND SCIENCE OF THE REPUBLIC OF KAZAKHSTANEAST KAZAKHSTAN STATE UNIVERSITY
THEM. S.AMANZHOLOVA
Faculty of Ecology and Natural Sciences
Department of Ecology and Life Safety
ABSTRACT
on the topic of:
Asteroids and comets
Do the following:
student EK-08-A
Vagner A.A.
Check l:
associate professor of the department
ecologists and and
security
life activity
Mayorov V.N.
Ust-Kamenogorsk, 2010
PLAN
1. Asteroids
2. Meteorites
3. Small fragments
4. Comets
Introduction
In the solar system except major planets and many of their companions are moving
so-called small bodies: asteroids, comets and meteorites. Small bodies
The solar system ranges in size from hundreds of microns to hundreds of kilometers.
Asteroids. From the point of view of physics, asteroids or, as they are also called, small
Planets are dense and durable bodies. Based on their composition and properties, they can be conditionally
divided into three groups: stone, iron-stone and iron. Asteroid
is a cold body. But he, like the Moon, for example, reflects the sun.
light, and therefore we can observe it as a star-shaped object. From here
and the name “asteroid” comes from, which in Greek means
star-shaped. Since asteroids move around the Sun, their position is
attitude towards the stars is constantly and quite quickly changing. That's why
Based on the initial sign, observers discover asteroids.
Comets, or "tailed stars", have been known since time immemorial. Comet is
complex physical phenomenon, which can be briefly described using several
concepts. The comet's nucleus is a mixture or, as they say, a conglomerate
dust particles, water ice and frozen gases. Ratio of dust content to
the ratio of gas in cometary nuclei is approximately 1:3. Sizes of comet nuclei, by
Scientists estimate that they range from 1 to 100 km. Currently being discussed
the possibility of the existence of both smaller and larger nuclei.
Known short-period comets have nuclei ranging in size from 2 to 10 km.
The size of the nucleus of the brightest comet Haley-Bopp, which was observed with the naked eye
eye in 1996, estimated at 40 km.
A meteoroid is a small body orbiting the Sun. Meteor is
a meteoroid that flew into the atmosphere of a planet and became heated to the point of brilliance. And if
its remnant fell to the surface of the planet, it is called a meteorite. Meteorite
considered “fallen” if there are eyewitnesses who observed its flight in the atmosphere; V
otherwise it is called "found".
Let us consider the above small bodies of the Solar System in more detail.
1. Asteroids
These cosmic bodies differ from planets primarily in their size. So,
the largest of the small planets, Ceres, is 995 km across;
next after it (in size): Palada - 560 km, Hygea - 380 km, Psyche - 240 km
etc. For comparison, we can point out that the smallest of the major planets, Mercury
has a diameter of 4878 km, i.e. 5 times greater than the diameter of Ceres, and the mass
they differ many hundreds of times.
The total number of small planets accessible to observation by modern telescopes is
is determined to be 40 thousand, but their total mass is 1 thousand times less than the mass of the Earth.
The movement of small planets around the Sun occurs in elliptical orbits, but
more elongated (the average eccentricity of their orbits is 0.51) than those of large
planets, and the inclination of their orbital planes to the ecliptic is greater than that of
major planets (average angle 9.54). Most of the planets revolve around
The Sun between the orbits of Mars and Jupiter, forming the so-called belt
asteroids. But there are also small planets whose orbits are closer to
Sun than the orbit of Mercury. The most distant ones are located behind Jupiter and even beyond
Saturn.
Space researchers have expressed various ideas about the cause of the large
concentrations of asteroids in a relatively narrow space of the interplanetary medium
between the orbits of Mars and Jupiter. One of the most common hypotheses
the origin of the asteroid belt bodies is the idea of destruction
mythical planet Phaethon. The very idea of the existence of a planet
is supported by many scientists and even seems to be supported by mathematical
calculations. However, the reason for the destruction of the planet remains inexplicable.
Various assumptions have been made. Some researchers believe that
the destruction of Phaeton occurred as a result of its collision with some large
body. According to others, the reasons for the collapse of the planet were explosive processes in
its depths. Currently, the problem of the origin of bodies in the asteroid belt
is an integral part of an extensive space exploration program in
international and national levels.
Among the small planets, a peculiar group of bodies stands out, the orbits of which
intersect with the Earth's orbit, and therefore there is a potential
the possibility of their collision with her. The planets of this group began to be called Apollo
object, or simply Apollo (Wetherill, 1979). For the first time about the existence of Apollo
has become known since the 30s of this century. In 1932 it was discovered
asteroid. He was named
Apollo 1932 HA. But it did not arouse much interest, although its name became
a common noun for all asteroids crossing the Earth's orbit.
In 1937, a cosmic body with a diameter of approximately 1 km passed 800
thousand km from the Earth and twice the distance from the Moon. Subsequently he was named
Hermes. To date, 31 such bodies have been identified, and each of them received
own name. Their diameters range from 1 to 8 km, and
The inclination of the orbital planes to the ecliptic ranges from 1 to 68.
Five of them orbit between Earth and Mars, and the remaining 26 -
between Mars and Jupiter (Wetherill, 1979). It is believed that out of 40 thousand small
There may be several planets in the asteroid belt with a diameter of more than 1 km
Cell Apollo. Therefore, the collision of such celestial bodies with the Earth is quite likely.
but at very long intervals.
It can be assumed that once a century one of these cosmic bodies may pass
near the Earth at a distance less than from us to the Moon, and once every 250 thousand years
there may be a collision with our planet. The impact of such a body highlights
energy equal to 10 thousand. Hydrogen bombs each with a power of 10 Mt. Wherein
a crater with a diameter of about 20 km should form. But such cases are rare and
human history is unknown. Hermes belongs to class III asteroids, and
after all, there are many such bodies of a larger size - classes II and I. Impact at
their collision with the Earth will naturally be even more significant.
When Uranus was discovered in 1781 its average heliocentric distance
turned out to correspond to the Titius-Bode rule, then in 1789 they began
search for a planet which, according to this rule, should have been located between
orbits of Mars and Jupiter, at an average distance of a=2.8 AU. from the sun. But
several German astronomers, led by K. Zach, decided to organize
collective searches. They divided the entire search for zodiac constellations into 24
plot and distributed among themselves for thorough research. But we didn't have time
astronomer J. Piatsii (1746-1826) discovered a star-shaped object through a telescope
seventh magnitude, slowly moving through the constellation Taurus.
The orbit of the object calculated by K. Gaus (1777-1855) turned out to be a planet,
corresponding to the Titius-Bode rule: semimajor axis a = 2.77 AU. And
eccentricity e=0.080. Piatsi named the newly discovered planet Ceres.
near Ceres there is another planet (8m), called Pallas (a = 2.77 AU,
a.u.), and March 29, 1807 - 4, Vesta (a=2.36 a.u.). All newly discovered planets
had a star-shaped appearance, without disks, indicating their small
geometric sizes. Therefore, these celestial bodies were called minor planets
or, according to the proposal of V. Herschel, asteroids (from the Greek “aster” - stellar and
"eidos" - view).
By 1891, about 320 asteroids had been discovered by visual methods. At the end
1891 German astronomer M. Wolf (1863-1932) proposed photographic
search method: with a 2-3 hour exposure, images of stars on a photographic plate
turned out to be point-like, and the trace of a moving asteroid was in the form of a small
dashes. Photographic techniques have led to a dramatic increase in discoveries
asteroids. Particularly intensive studies of small planets are now being carried out
at the Institute of Theoretical Astronomy (in St. Petersburg) and in the Crimean
Astrophysical Observatory of the Russian Academy of Sciences.
Asteroids whose orbits are reliably determined are given a name and ordinal number.
number. Over 3,500 such asteroids are now known, but in the solar system
much bigger.
From the specified number known asteroids astronomers of the Crimean Astrophysical
observatories were opened about 550, perpetuating the names of famous people in their names
of people.
The vast majority (up to 98%) of known asteroids move between
orbits of Mars and Jupiter, at average distances from the Sun from 2.06 to 4.30
a.e. (circulation periods from 2.96 to 8.92 years). However, there are asteroids
with unique orbits, and are given masculine names, usually from
Greek mythology.
The first three of these minor planets move outside the asteroid belt, and in
perihelion, Icarus approaches the Sun twice as close as Mercury, and Hermes and Adonis -
closer to Venus. They can approach the Earth at a distance of 6 million to 23 million.
km, and Hermes in 1937 passed close to the Earth even at a distance of 580 thousand km,
orbit of Saturn. But Hidalgo is no exception. Behind last years
About 10 asteroids have been discovered whose perihelia are located near their orbits
planets terrestrial group, and aphelion - near the orbits of Jupiter. Such orbits
are characteristic of comets of the Jupiter family and indicate a possible common
origin of asteroids and comets.
In 1977, a unique asteroid was discovered that orbits the Sun along
orbit with semimajor axis a=13.70 AU. and eccentricity e=0.38, so in
perihelion (q = 8.49 AU) it enters the orbit of Saturn, and at aphelion (Q = 18.91
a.e.) is approaching the orbit of Uranus. He is named Chiron. Apparently there are
and other similar distant asteroids, the search for which continues.
The brightness of most known asteroids during opposition is from 7 m
up to 16 m, but there are also weaker objects. The brightest (up to 6 m
) is Vesta.
The diameters of asteroids are calculated by their brightness and reflectivity in
visual and infrared rays. It turned out that there are not so many large asteroids
a lot of. The largest are Ceres (1000 km across), Pallas (610 km),
Vesta (540 km) and Hygia (450 km). Only 14 asteroids have diameters greater than 250
km, while the rest have less, up to 0.7 km. Bodies of such small sizes do not
may be spheroidal in shape, and all asteroids (except perhaps the most
large) are shapeless blocks.
The masses of asteroids are extremely different: the largest is close to 1.5 .
10 21 kg (i.e. 4 thousand times less than the mass of the earth), Ceres has.
The total mass of all asteroids does not exceed 0.001 Earth masses. Of course everything
these celestial bodies are devoid of atmosphere. Many asteroids have a regular
Axial rotation was detected in the change in their brightness.
In particular, the rotation period of Ceres is 9.1 hours, and that of Pallas is 7.9 hours.
Icarus rotates the fastest, in 2 hours 16 meters.
The study of the reflectivity of many asteroids made it possible to combine them
into three main groups: dark, light and metallic. Surface of dark
asteroids reflect only up to 5% of the sunlight falling on it and
consists of substances similar to black basalt and carbonaceous rocks. These
asteroids are often called carbonaceous. Light asteroids reflect from 10% to 25%
sunlight, which makes their surface similar to silicon compounds - this
rocky asteroids. Metal asteroids (an absolute minority) too
light, but in terms of their reflective properties their surface is similar to
iron-nickel alloys. This division of asteroids is confirmed by
the chemical composition of meteorites falling on Earth. Minor number
The studied asteroids do not belong to any of the three main groups.
It is significant that a band was discovered in the spectra of carbonaceous asteroids
water absorption (l= 3 µm). In particular, the surface of the asteroid Ceres consists
from minerals similar to earthly clays and containing about 10% water.
With small sizes and masses of asteroids, the pressure in their interiors is low: even
for the largest asteroids it does not exceed 7 10 5
8 10 5 GPa (700 - 800 atm) and cannot cause heating of their solids
cold subsoil Only the surface of asteroids is heated very weakly far from
them by the Sun, but even this insignificant energy is radiated into the interplanetary
space. Surface temperature calculated according to the laws of physics
the vast majority of asteroids turned out to be close to 150 - 170 K
(-120...-100°С).
And only a few asteroids that pass close to the Sun have a surface of
During such periods it gets very hot. Thus, the surface temperature of Icarus
rises to almost 1000 K (+730°C), and when moving away from the Sun again sharply
goes down.
The orbits of other asteroids are subject to significant disturbances from
gravitational influence of large planets, mainly Jupiter. Especially
Small asteroids experience strong disturbances, which leads to
collisions of these bodies and their fragmentation into fragments of a wide variety of sizes
B from hundreds of meters in diameter to specks of dust.
Currently, the physical nature of asteroids is being studied because
it can trace the evolution (development) of the substance from which it was formed
Solar system.
2. Meteorites
A variety of meteoroids move in near-Earth space
(cosmic fragments of large asteroids and comets). Their speeds are in
range from 11 to 72 km/s. It often happens that the paths of their movement
intersect with the Earth's orbit and they fly into its atmosphere.
Meteorites are stone or iron bodies falling to Earth from interplanetary
space. The fall of meteorites to Earth is accompanied by sound, light and
mechanical phenomenon. A bright fireball called
a fireball, accompanied by a tail and flying sparks. After
the car disappears, after a few seconds explosion-like impacts are heard,
called shock waves, which sometimes cause significant shaking
soil and buildings.
The phenomena of intrusion of cosmic bodies into the atmosphere have three main stages:
1. Flight in a rarefied atmosphere (up to altitudes of about 80 km), where interaction
air molecules are carpuscular in nature. Air particles collide with
body, stick to it or are reflected and transfer part of their energy to it. Body
heats up from the continuous bombardment of air molecules, but does not experience
noticeable resistance, and its speed remains almost unchanged. In this
stage, however, the outer part of the cosmic body heats up to a thousand degrees
and higher. Here the characteristic parameter of the problem is the ratio of the free length
range to the body size L, which is called the Knudsen number K n. IN
in aerodynamics it is customary to take into account the molecular approach to air resistance when
K n >0.1.
2. Flight in the atmosphere in the mode of continuous flow of air around the body, then
is when air is considered a continuous medium and has an atomic-molecular character
its composition is clearly not taken into account. At this stage, there appears in front of the body
a head shock wave, followed by a sharp increase in pressure and temperature.
The body itself is heated due to convective heat transfer, as well as due to
radiation heating. Temperatures can reach several tens of thousands
degrees, and pressure up to hundreds of atmospheres. When braking sharply they appear
significant overloads. Deformations of bodies, melting and evaporation occur
surfaces, mass entrainment by incoming air flow (ablation).
3. When approaching the surface of the Earth, the air density increases,
The body's resistance increases, and it either practically stops at
any height, or continues on its way until it directly collides with the Earth. At
In this case, large bodies are often divided into several parts, each of which
falls separately to Earth. With strong deceleration of cosmic mass above the Earth
the accompanying shock waves continue their movement towards the surface
Earth, are reflected from it and produce disturbances in the lower layers of the atmosphere, and
Also earth's surface.
The fall process of each meteoroid is individual. There is no possibility in short
In the story, describe all possible features of this process.
There are significantly more “found” meteorites than “fallen” ones. They are often found
tourists or peasants working in the field. Because meteorites have a dark
color and are easily distinguishable in the snow, great place are used to find them
ice fields of Antarctica, where thousands of meteorites have already been found. First meteorite
discovered in Antarctica in 1969 by a group of Japanese geologists studying glaciers.
They found 9 fragments lying nearby, but belonging to four different types
meteorites. It turned out that meteorites that fell on the ice in different places,
gather where glacial ice moving at a speed of several meters per year
fields stop, resting on mountain ranges. The wind destroys and dries
upper layers of ice (dry sublimation occurs - ablation), and meteorites
concentrated on the surface of the glacier. Such ice has a bluish color and
easily distinguishable from the air, which is what scientists use when studying places,
promising for collecting meteorites.
An important meteorite fall occurred in 1969 in Chihuahua (Mexico). First of
many large fragments were found near a house in the village of Pueblito de
Allende, and, following tradition, all found fragments of this meteorite were
united under the name Allende. The fall of the Allende meteorite coincided with the beginning
lunar program "Apollo" and gave scientists the opportunity to work out methods
analysis of extraterrestrial samples. In recent years it has been found that some
meteorites containing white debris embedded in a darker parent
rock are lunar fragments.
The Allende meteorite belongs to chondrites, an important subgroup of rocks.
meteorites. They are called so because they contain chondrules (from the Greek.
chondros, grain) - the oldest spherical particles condensed into
protoplanetary nebula and then included in later rocks.
Such meteorites make it possible to estimate the age of the Solar system and its
original composition. The inclusions of the Allende meteorite, rich in calcium and aluminum,
the first to condense due to their high boiling point, have
age measured from radioactive decay is 4.559 ± 0.004 billion years. This
the most accurate estimate of the age of the solar system. Moreover, all meteorites
carry "historical records" caused by long-term influence on them
galactic cosmic rays, solar radiation and solar wind.
Having examined the damage caused cosmic rays, you can tell how long
The meteorite was in orbit before it came under the protection of the earth's atmosphere.
The direct connection between meteorites and the Sun follows from the fact that
the elemental composition of the oldest meteorites - chondrites - exactly repeats
composition of the solar photosphere. The only elements whose content
differs - these are volatiles, such as hydrogen and helium, which evaporated abundantly
from meteorites during their cooling, as well as lithium, partially “burnt” on
The sun in nuclear reactions. Concepts " solar composition" and "chondrite composition"
used as equivalent when describing the above-mentioned “recipe for solar
substances." Stony meteorites, the composition of which differs from that of the sun,
called achondrites.
3. Small fragments.
The near-solar space is filled with small particles, the sources of which are
collapsing nuclei of comets and collisions of bodies, mainly in the belt, serve
asteroids. The smallest particles gradually approach the Sun as a result
Poynting-Robertson effect (it lies in the fact that the solar pressure
light on a moving particle is directed not exactly along the Sun-particle line, but in
as a result of aberration, the light is deflected back and therefore slows down the movement
particles). The fall of small particles on the Sun is compensated by their constant
reproduction, so that in the ecliptic plane there is always a cluster
dust that scatters the sun's rays. On the darkest nights it is noticeable in the form
zodiacal light stretching in a wide strip along the ecliptic in the west after
sunset and in the east before sunrise. Near the Sun, zodiacal light
goes into false crown ( F-crown, from false – false), which is visible
only during a total eclipse. With increasing angular distance from the Sun, the brightness
zodiacal light quickly decreases, but at the antisolar point of the ecliptic it again
intensifies, forming counter-radiance; this is caused by small dust particles
Intensively reflect light back.
From time to time, meteoroids enter the Earth's atmosphere. The speed of their movement
so great (on average 40 km/s) that almost all of them, except the smallest and most
large ones, burn at an altitude of about 110 km, leaving long luminous tails -
meteors, or shooting stars. Many meteoroids are associated with the orbits of individual
comets, so meteors are observed more often when the Earth at certain times
Lots of meteors observed as Earth crosses the Perseid shower
associated with particles lost by comet 1862 III. Another stream - Orionids
Particles smaller than 30 microns can be decelerated in the atmosphere and fall to
the ground without burning; such micrometeorites are collected for laboratory analysis.
If particles of several centimeters or more in size consist of sufficient
dense substance, they also do not burn entirely and fall to the surface
Earth in the form of meteorites. More than 90% of them are stone; distinguish them from earthly ones
only a specialist can breed. The remaining 10% of meteorites are iron (in
in reality they are composed of an alloy of iron and nickel).
Meteorites are considered to be asteroid fragments. Iron meteorites were once in
composition of the nuclei of these bodies destroyed by collisions. Perhaps some are loose and
volatile-rich meteorites originate from comets, but this
unlikely; most likely, large particles of comets burn up in the atmosphere, and
Only small ones are preserved. Considering how difficult it is for comets and
asteroids, it is clear how useful it is to study meteorites on your own
“arrived” on our planet from the depths of the solar system.
4. Comets
Comets are the most effective celestial bodies in the solar system.
Comets are a kind of cosmic icebergs consisting of frozen
gases, complex chemical composition, water ice and refractory
mineral matter in the form of dust and larger fragments.
Although comets, like asteroids, move around the Sun in conical curves,
Outwardly, they are strikingly different from asteroids. If the asteroids shine
reflected sunlight and in the field of view of the telescope resemble slowly
moving weak stars, then comets intensively scatter sunlight into
some of the most characteristic parts of the spectrum for comets, and therefore many
comets are visible to the naked eye, although the diameters of their nuclei rarely exceed 1 -
5 km.
Comets are of interest to many scientists: astronomers, physicists, chemists, biologists,
gas dynamics, historians, etc. And this is natural. After all, comets suggested
scientists that the solar wind blows in interplanetary space; possibly comets
are the “culprits” for the emergence of life on Earth, since they could have been brought into
Earth's atmosphere complex organic compounds. In addition, comets
apparently carry valuable information about the initial stages of protoplanetary
clouds from which the Sun and planets were also formed.
When you first meet a bright comet, it may seem that the tail is the most
the main part of the comet. But if in the etymology of the word "comet" the tail appeared
The main reason for such a name is from a physical point of view
the tail is a secondary formation, developed from a rather tiny
the nucleus, the most important part of the comet as a physical object. Comet nuclei -
the root cause of the rest of the complex of cometary phenomena that are still
are still not accessible to telescopic observations, since they are veiled
the luminous matter surrounding them, continuously flowing from the nuclei. Applying
higher magnifications, you can look into the deeper layers of the luminous surroundings
core of the gas-dust shell, but what remains will be in size
still significantly exceed the true size of the nucleus. Central condensation
visible in the diffuse atmosphere of a comet visually and in photographs is called
photometric core. It is believed that the core itself is located in its center
comets, i.e. The center of mass of the comet is located.
The foggy atmosphere surrounding the photometric core and gradually descending to
no, merging with the background of the sky is called coma. Coma together with the nucleus constitute
comet head Far from the Sun, the head looks symmetrical, but with
approaching the Sun, it gradually becomes oval, then the head
lengthens even more, and in the side opposite from the Sun from it
the tail develops.
So, the nucleus is the most important part of the comet. However, there is still no consensus
opinions about what it really is. Back in the time of Bessel and
Laplace had the idea of a comet's nucleus as a solid body,
consisting of easily evaporating substances such as ice or snow, quickly
transforming into the gas phase under the influence of solar heat. This icy
The classical model of the cometary nucleus was significantly expanded and developed in
Lately. The most widely recognized among comet researchers is
Whipple's model of the core - a conglomerate of refractory rocky rocks
particles and frozen volatile components (CH4, CO2, H2O, etc.). In such a core
ice layers of frozen gases alternate with dust layers. As
heating gases such as evaporating “dry ice” by solar heat
break out, carrying clouds of dust with them. This allows, for example,
explain the formation of gas and dust tails in comets, as well as the ability
small comet nuclei to active gas evolution.
The heads of comets take on a variety of shapes as comets move in orbit.
Far from the SUN, the heads of comets are round, which is explained by the weak impact
solar radiation on the particles of the head, and its outlines are determined by isotropic
expansion of cometary gas into interplanetary space. These are tailless
comets that resemble globular star clusters in appearance. Approaching
toward the Sun, the comet's head takes the shape of a parabola or catenary.
The parabolic shape of the head is explained by the “fountain” mechanism. Education
heads in the form of a chain line is associated with the plasma nature of the cometary atmosphere and
the influence of the solar wind on it and the magnetic field it carries.
Sometimes the comet's head is so small that the comet's tail appears to protrude
directly from the kernel. In addition to changing the outlines in the heads of comets, then
various structural formations appear and disappear: tacks, shells,
rays, outpourings from the core, etc.
Large comets with tails stretching far across the sky have been observed from
ancient times. It was once assumed that comets belonged to the
atmospheric phenomena. This misconception was refuted by Brahe, who discovered that
the comet of 1577 occupied the same position among the stars when observed from
different points, and, therefore, is further away from us than the Moon.
The movement of comets across the sky was first explained by Halley (1705), who found that
their orbits are close to parabolas. He determined the orbits of 24 bright comets, and
it turned out that the comets of 1531 and 1682 have very similar orbits. From here
Halley concluded that this is the same comet that is moving around
The Sun is in a very elongated ellipse with a period of about 76 years. Halley
predicted that in 1758 it should appear again in December 1758
it was indeed discovered. Halley himself did not live to see this time and did not
could see how brilliantly his prediction was confirmed. This comet (one of
brightest) was named Halley's Comet.
Comets are designated by the names of the people who discovered them. In addition, the newly opened
the comet is given a provisional designation based on the year of discovery from
by adding a letter indicating the sequence of the comet's passage through
perihelion in a given year.
Only a small fraction of the comets observed each year are
periodic, i.e. known from their previous appearances. Most of
comets move in very elongated ellipses, almost parabolas. Periods
their appeals are not precisely known, but there is reason to believe that they reach
many millions of years. Such comets move away from the Sun at distances
comparable to interstellar ones. The planes of their almost parabolic orbits are not
concentrated towards the ecliptic plane and randomly distributed in space
way. Direct direction of movement occurs as often as
the opposite.
Periodic comets move in less elongated elliptical orbits and
have completely different characteristics. Of the 40 comets observed, more than 1
times, 35 have orbits inclined less than 45^ to the ecliptic plane.
Only Halley's Comet has an orbit with an inclination greater than 90^ and,
therefore moves in reverse direction. Among short-period
(i.e. having periods of 3 - 10 years) comets are distinguished as the “Jupiter family”
large group comets whose aphelions are the same distance from the Sun
distance like the orbit of Jupiter. It is assumed that the "Jupiter family"
formed as a result of the capture planet of comets, which previously moved along
more elongated orbits. Depending on the relative position of Jupiter and
comets, the eccentricity of the cometary orbit can both increase and
decrease. In the first case, there is an increase in the period or even a transition
into a hyperbolic orbit and the loss of the comet by the Solar System, in the second -
decreasing period.
The orbits of periodic comets are subject to very noticeable changes. Sometimes
the comet passes near the Earth several times, and then, due to the gravity of the planets,
giants are thrown into a more distant orbit and become unobservable.
In other cases, on the contrary, a comet that has never been observed before
becomes visible due to the fact that it passed near Jupiter or Saturn and
changed its orbit sharply. In addition to such drastic changes, known only to
limited number of objects, the orbits of all comets experience gradual
changes.
Orbital changes are not the only possible reason disappearance
comets It has been reliably established that comets are quickly destroyed. Brightness
short-period comets weaken over time, and in some cases
the destruction process was observed almost directly. Classic example
is Comet Biely. It was discovered in 1772 and observed in 1813,
1826 and 1832. In 1845, the size of the comet turned out to be increased, and in
January 1846 observers were surprised to discover two very close comets
instead of one. The relative movements of both comets were calculated, and it turned out that
that Comet Biely split into two about a year ago, but at first
components were designed one on top of the other, and separation was not noticed
straightaway. Comet Biely was observed one more time, with one component being many
weaker than the other, and she could not be found again. But it was observed several times
meteor shower whose orbit coincided with the orbit of Comet Biele.
When solving the question of the origin of comets, one cannot do without knowledge
chemical composition the substance that makes up a comet's nucleus. It would seem that,
What could be simpler? We need to photograph more spectra of comets,
decipher them - and the chemical composition of cometary nuclei will immediately become clear to us
famous. However, the matter is not as simple as it seems at first glance.
The spectrum of the photometric core can simply be reflected solar or
emission molecular spectrum. The reflected solar spectrum is
continuous and does not report anything about the chemical composition of the area from which
it was reflected - by the core or the dust atmosphere surrounding the core. Emission
the gas spectrum carries information about the chemical composition of the gas atmosphere,
surrounding the core, and also tells us nothing about the chemical composition
surface layer of the nucleus, since molecules emitting in the visible region,
such as C2, CN, CH, MH, OH, etc., are secondary, daughter molecules
- “fragments” of more complex molecules or molecular complexes, of which
a comet's nucleus is formed. These complex parent molecules evaporate into
perinuclear space, are quickly exposed to destructive effects
solar wind and photons either decay or dissociate into more
simple molecules, the emission spectra of which can be observed from comets.
The parent molecules themselves produce a continuous spectrum.
The Italian Donati was the first to observe and describe the spectrum of the comet's head. On the background
faint continuous spectrum of comet 1864, he saw three broad luminous
stripes: blue, green and yellow. As it turned out, this coincidence
belonged to molecules of carbon C2, which appeared in abundance in the cometary
atmosphere. These emission bands of C2 molecules are called Swan bands,
named after the scientist who studied the spectrum of carbon. First
slit spectrogram of the head Great Comet 1881 was received by an Englishman
Heggins, who discovered the emission of a chemically active radical in the spectrum
cyan CN.
Far from the Sun, at a distance of 11 AU, the approaching comet looks like
a small foggy speck, sometimes with signs of incipient formation
tail The spectrum obtained from a comet located at such a distance, and
up to a distance of 3-4 AU, is continuous, because on such large
distances, the emission spectrum is not excited due to weak photon and
corpuscular solar radiation.
This spectrum is formed as a result of the reflection of sunlight from dust particles.
particles or as a result of its dispersion on polyatomic molecules or
molecular complexes. At a distance of about 3 AU. from the Sun, i.e. When
cometary nucleus crosses the asteroid belt, the first one appears in the spectrum
emission band of the cyanogen molecule, which is observed in almost the entire head
comets. At a distance of 2 AU radiation from triatomic molecules is already excited
C3 and NH3, which are observed in a more limited area of the comet's head
near the nucleus than the ever-increasing CN radiation. At a distance of 1.8 AU
carbon emissions appear - Swan bands, which immediately become
visible throughout the comet's head: both near the nucleus and at the boundaries of the visible head.
The mechanism of the glow of cometary molecules was deciphered back in 1911.
K. Schwarzschild and E. Krohn, who, studying the emission spectra of Halley's comet
(1910), concluded that the molecules of cometary atmospheres are resonant
re-emit sunlight. This glow is similar to the resonant glow
sodium vapor in the famous experiments of Auda, who was the first to notice that when
When illuminated by light having the frequency of the sodium yellow doublet, the sodium vapor itself
begin to glow at the same frequency with a characteristic yellow light. This -
mechanism of resonance fluorescence, which is a frequent case of a more general
luminescence mechanism. Everyone knows the glow of fluorescent lamps above
shop windows, fluorescent lamps, etc. Similar mechanism
makes the gases in comets glow.
To explain the glow of the green and red oxygen lines (similar
lines are also observed in the spectra of auroras) various
mechanisms: electron impact, dissociative recombination and photodissipation.
Electron impact, however, is unable to explain the higher
the intensity of the green line in some comets compared to the red line.
Therefore, more preference is given to the photodissociation mechanism, in favor of
which is indicated by the distribution of brightness in the head of the comet. However, this
the question has not yet been finally resolved and the search for the true mechanism of atomic luminescence
in comets continue. The issue of parental,
primary molecules that make up the cometary nucleus, and this question is very
important, since it is the chemistry of the nuclei that determines the unusually high activity
comets capable of developing giant nuclei from very small nuclei
atmospheres and tails, exceeding in size all known bodies in
Solar system.
Literature
1. V.A. Brashtein “Planets and their observation” Moscow “Science” 1979.
2. S. Dole “Planets for People” Moscow “Science” 1974.
3. K.I. Churyumov “Comets and their observation” Moscow “Science” 1980.
4. E.L. Krinov “Iron Rain” Moscow “Science” 1981.
5. K.A. Kulikov, N.S. Sidorenkov “Planet Earth” Moscow “Science”
6. B.A. Vorontsov - Velyaminov “Essays on the Universe” Moscow “Science”
7. N.P. Erpyleev “Encyclopedic Dictionary of a Young Astronomer” Moscow
“Pedagogy” 1986.
8. E.P. Levitan “Astronomy” Moscow “Enlightenment” 1994
The small bodies of the Solar System include asteroids, meteoroids, comets, Kuiper belt bodies. Asteroids are less than a thousand kilometers in size. More small bodies, than asteroids, are called "meteoroids" or meteoroid bodies, they can be on the order of several meters or even smaller.
Asteroid- a small planet-like body in the solar system, ranging in size from several meters to thousands of kilometers, asteroids are often called minor planets(but not dwarf planets!) Most asteroid orbits are concentrated in the main asteroid belt between the orbits of Mars and Jupiter.
History of the discovery of asteroids.
On January 1, 1801, Italian astronomer Giuseppe Piazzi accidentally discovered a star whose declination changed noticeably over the course of 24 hours of observation; this object was located between Mars and Jupiter. This object was named Ceres after the ancient Roman goddess of fertility. Thus, astronomers discovered a new type of objects in the solar system, later called asteroids. Observing the movement of Ceres, the German physician Heinrich Wilhelm Olbers discovered a new asteroid in 1802, which was named Pallas in honor of the ancient Greek goddess Pallas Athena. Juno was discovered in 1804, Vesta in 1807. Friedrich Wilhelm Herschel proposed calling small planets asteroids. Asteroid means "star-shaped" in Greek.
In 1804, Olbers expressed the famous hypothesis about the rupture of the hypothetical planet Phaeton between Mars and Jupiter and the formation of asteroids - its fragments. Since 2006, the first asteroid found, Ceres, has been classified as a dwarf planet. Asteroids near the Earth and their danger to the planet
Hazardous space objects, such as asteroids whose orbits intersect the Earth’s orbit, represent serious threat the existence of human civilization during a collision between the Earth and an asteroid. The number of asteroids crossing the Earth's orbit and having a diameter of more than 1 km is approximately 500.
In recent years large asteroids flew by repeatedly, causing fear and anxiety. In 1936, the Adonis asteroid flew 2 million km from the Earth; in 1937, the Hermes asteroid flew at a distance of 800 thousand km from the Earth. In 1996, the Tautatis asteroid flew at a distance of 450 thousand km from Earth
A significant part of the main belt asteroids move along stable, stable orbits, which have changed little over the past 4.5 billion years, so collisions with such asteroids are practically unlikely.
But the orbits of asteroids can change when approaching giant planets or when colliding with other asteroids and comets, so the orbits of asteroids can change.
The American astronomer R. Binzel developed a high-quality a scale for assessing the risk of collisions with the Earth by asteroids and comets, similar to the Richter scale, used to gradate earthquake hazards. In 1999, the scale was approved by the International Astronomical Union. (show table on presentation slide). According to various estimates, there is a high probability of an asteroid with a diameter of about 1 km falling to Earth once every 100 thousand years. But the greatest probability is that the Earth will encounter smaller celestial objects.
Several double asteroids have been discovered.
In 1993, the American spacecraft Galileo, heading towards Jupiter, crossed the main asteroid belt. It turned out that the asteroid Ida has a small satellite called Dactyl.
Asteroid Eros revolves around the Sun with a period of 1.8 Earth years. Its dimensions are 40 x 14 x 14 km. In 2000, the robotic NEAR-Shoemaker spacecraft took many photographs of the asteroid. Studies of the asteroid have shown that Eros is a monolithic solid, that its chemical composition is approximately homogeneous, and that it was formed in the “young years” of the Solar System. In 2001, the device landed on the surface of an asteroid.
Asteroid 216 Cleopatra consists mainly of metals such as nickel and iron, as shown by radar studies.
Asteroid 951 Gaspra has dimensions of 19x12x11 km and orbits in an almost circular orbit within the main asteroid belt. Gaspra consists of a mixture rocks and metal-containing minerals.
Asteroids beyond the orbit of Jupiter.
Other asteroids were discovered beyond the orbit of Jupiter at the end of the 20th century. The second asteroid belt is called the Kuiper belt.
The Kuiper Belt is a disk-shaped region beyond the orbit of Neptune, at a distance of 30 AU. up to 100 a.u. from the Sun, populated by asteroids and comet nuclei.
It is assumed that Kuiper belt objects are ice with small admixtures of organic substances, that is, they are close in composition to cometary matter. The mass of all Kuiper belt objects exceeds the mass of all asteroids in the main asteroid belt. But it is assumed that the mass of Orth cloud objects exceeds the mass of Kuiper belt objects.
Comets- the most numerous, most extensive and most amazing celestial bodies of the Solar System. The word “comet” translated from Greek means “hairy”, “long-haired”. As the comet approaches the Sun, it takes on a spectacular appearance, heating up under the influence of the sun's heat so that gas and dust fly away from the surface, forming a bright tail.
According to scientists, on the distant outskirts of the solar system, in the so-called Oort cloud - a giant spherical accumulation of cometary matter - there are about 10 12 -10 13 comets orbiting the Sun. As the comet approaches the Sun, the ice of the comet's nucleus begins to evaporate, and streams of gas and dust begin to be released into space.
- Comet structure
Each comet has several different parts:
- Core: Relatively solid and stable, consisting mainly of ice and gas with minor additions of dust and other solids.
- Head (coma): a luminous gas shell arising under the influence of electromagnetic and corpuscular radiation from the Sun. A dense cloud of water vapor, carbon dioxide and other neutral gases sublimating from the core.
- Dust tail: consists of very small dust particles carried away from the core by a gas flow. This part of the comet is best visible to the naked eye.
- Plasma (ion) tail: consists of plasma (ionized gases), interacts intensely with the solar wind.
The structure of comets and the features of comet tails are best illustrated using the “Comets” and “Comets: structure” models.
Meteor bodies
There is no clear distinction between meteoroids (meteor bodies) and asteroids. Usually meteoroids are bodies measuring less than a hundred meters, and larger ones by asteroids. The collection of meteoroids forming around the Sun forms meteoric material in interplanetary space. A certain proportion of meteoroids are the remnants of the substance from which the Solar System was once formed, some are the remnants of the constant destruction of comets, and fragments of asteroids.
meteor body or meteoroid- a solid interplanetary body that, when entering the atmosphere of a planet, causes a phenomenon meteor and sometimes ends with a fall to the surface of the planet meteorite.
What usually happens when a meteoroid reaches the Earth's surface? Usually nothing, since due to their small size meteor bodies burn up in the Earth's atmosphere. Large clusters meteor bodies are called meteor swarm. During the approach of a meteor swarm to the Earth, meteor showers .
- Meteors and fireballs
The phenomenon of combustion of a meteoroid in the atmosphere of a planet is called meteor. A meteor is a short-term flash, the combustion trail disappears after a few seconds.
About 100,000,000 meteoroids burn up in the Earth's atmosphere per day.
If the meteor trails are continued back, they will intersect at one point called meteor shower radiant.
Many meteor showers are periodic, repeating year after year, and are named after the constellations in which their radiants lie. Thus, the meteor shower, observed annually from approximately July 20 to August 20, is called the Perseids because its radiant lies in the constellation Perseus. The Lyrids (mid-April) and Leonids (mid-November) meteor showers respectively get their name from the constellations Lyra and Leo.
It is extremely rare that meteoroid bodies are relatively large in size, in which case they say that they are observing car. Very bright fireballs are visible during the day.
- Meteorites
If the meteor body is large enough and could not completely burn up in the atmosphere during its fall, then it falls onto the surface of the planet. Such meteoroids falling to Earth or another celestial body are called meteorites.
The most massive meteoroids with high speed fall onto the Earth's surface to form crater.
Depending on the chemical composition, meteorites are divided into stone (85 %), iron (10%) and iron-stone meteorites (5%).
Stone meteorites consist of silicates with inclusions of nickel iron. Therefore, heavenly stones are usually heavier than earthly ones. The main mineralogical components of the meteorite substance are iron-magnesium silicates and nickel iron. More than 90% of stony meteorites contain round grains - chondrules . Such meteorites are called chondrites.
Iron meteorites almost entirely composed of nickel iron. They have an amazing structure, consisting of four systems of parallel kamacite plates with a low nickel content and interlayers consisting of taenite.
Stone-iron meteorites consist half of silicates, half of metal. They have a unique structure, not found anywhere except meteorites. These meteorites are either metallic or silicate sponges.
One of the largest iron meteorites, the Sikhote-Alin meteorite, which fell on the territory of the USSR in 1947, was found in the form of a scattering of many fragments.
Since ancient times, people have sought to uncover the secrets that the sky holds. Since the first telescope was created, scientists have been gradually collecting grains of knowledge that are hidden in the boundless expanses of space. It's time to find out where the messengers from space - comets and meteorites - came from.
What is a comet?
If we examine the meaning of the word "comet", we come to its ancient Greek equivalent. Literally it means “with long hair.” Thus, the name was given in view of the structure of this Comet, which has a “head” and a long “tail” - a kind of “hair”. The head of a comet consists of a nucleus and perinuclear substances. The loose core may contain water, as well as gases such as methane, ammonia and carbon dioxide. The comet Churyumov-Gerasimenko, discovered on October 23, 1969, has the same structure.
How the comet was previously represented
In ancient times, our ancestors revered her and invented various superstitions. Even now there are those who associate the appearance of comets with something ghostly and mysterious. Such people may think that they are wanderers from another world of souls. Where did this come from? Perhaps the whole point is that the appearance of these heavenly creatures ever coincided with some unkind incident.
However, as time passed, the idea of what small and large comets were changed. For example, a scientist like Aristotle, studying their nature, decided that it was a luminous gas. After a while, another philosopher named Seneca, who lived in Rome, suggested that comets are bodies in the sky moving in their orbits. However, real progress in their study was achieved only after the creation of the telescope. When Newton discovered the law of gravity, things took off.
Current ideas about comets
Today, scientists have already established that comets consist of a solid core (from 1 to 20 km in thickness). What does the comet's nucleus consist of? From a mixture of frozen water and cosmic dust. In 1986, photographs of one of the comets were taken. It became clear that its fiery tail is an emission of a stream of gas and dust, which we can observe from the earth's surface. For what reason does this “fiery” emission occur? If an asteroid flies very close to the Sun, then its surface heats up, which leads to the release of dust and gas. Solar energy exerts pressure on the solid material that makes up the comet. As a result, a fiery tail of dust is formed. This debris and dust is part of the trail that we see in the sky when we observe the movement of comets.
What determines the shape of a comet's tail?
The post on comets below will help you better understand what comets are and how they work. They come in different varieties, with tails of all sorts of shapes. It's all about the natural composition of the particles that make up this or that tail. Very small particles quickly fly away from the Sun, and larger ones, on the contrary, tend to the star. What is the reason? It turns out that the former move away, pushed by solar energy, while the latter are affected by the gravitational force of the Sun. As a result of these physical laws, we get comets whose tails are curved in different ways. Those tails that are largely composed of gases will be directed away from the star, while corpuscular tails (consisting mainly of dust), on the contrary, will tend to the Sun. What can you say about density? comet tail? Cloud tails can typically measure millions of kilometers, in some cases hundreds of millions. This means that, unlike the body of a comet, its tail consists largely of discharged particles, having practically no density. When an asteroid approaches the Sun, the comet's tail can bifurcate and acquire a complex structure.
The speed of particle movement in a comet's tail
Measuring the speed of movement in a comet's tail is not so easy, since we cannot see individual particles. However, there are cases when the speed of movement of matter in the tail can be determined. Sometimes gas clouds can condense there. From their movement, the approximate speed can be calculated. So, the forces moving the comet are so great that the speed can be 100 times greater than the gravity of the Sun.
How much does a comet weigh?
The entire mass of comets largely depends on the weight of the comet's head, or more precisely, its nucleus. Presumably, the small comet could weigh only a few tons. Whereas, according to forecasts, large asteroids can reach a weight of 1,000,000,000,000 tons.
What are meteors
Sometimes one of the comets passes through the Earth's orbit, leaving a trail of debris in its wake. When our planet passes by the place where the comet was, these debris and cosmic dust remaining from it enter the atmosphere at great speed. This speed reaches more than 70 kilometers per second. When the comet's fragments burn up in the atmosphere, we see a beautiful trail. This phenomenon is called meteors (or meteorites).
Age of comets
Fresh asteroids of enormous size can survive in space for trillions of years. However, comets, like any other one, cannot exist forever. The more often they approach the Sun, the more they lose the solid and gaseous substances that make up their composition. “Young” comets can lose a lot of weight until a kind of protective crust forms on their surface, which prevents further evaporation and burning out. However, the “young” comet ages, and the nucleus becomes decrepit and loses its weight and size. Thus, the surface crust acquires many wrinkles, cracks and breaks. Gas streams, burning, push the body of the comet forward and forward, giving speed to this traveler.
Halley's Comet
Another comet, the structure is the same as the comet Churyumov - Gerasimenko, is an asteroid discovered by Edmund Halley. He realized that comets have long elliptical orbits in which they move at large intervals. He compared comets that were observed from the earth in 1531, 1607 and 1682. It turned out that it was the same comet, which moved along its trajectory after a period of time equal to approximately 75 years. In the end, she was named after the scientist himself.
Comets in the Solar System
We are in the solar system. At least 1000 comets have been found near us. They are divided into two families, and they, in turn, are divided into classes. To classify comets, scientists take into account their characteristics: the time it takes them to travel the entire path in their orbit, as well as the period from orbit. If we take Halley's Comet mentioned earlier as an example, it completes a full revolution around the sun in less than 200 years. It belongs to periodic comets. However, there are those that cover the entire path in much shorter periods of time - the so-called short-period comets. We can be sure that in our solar system there is great amount periodic comets whose orbits around our star. Such celestial bodies can move so far from the center of our system that they leave Uranus, Neptune and Pluto behind. Sometimes they can come very close to planets, causing their orbits to change. An example is Comet Encke.
Comet Information: Long Period
Trajectory of movement long-period comets very different from short-period ones. They go around the Sun from all sides. For example, Heyakutake and Hale-Bopp. The latter looked very spectacular when they approached our planet for the last time. Scientists have calculated that the next time they can be seen from Earth will be thousands of years later. A lot of comets with a long period of movement can be found at the edge of our solar system. Back in the mid-20th century, a Dutch astronomer suggested the existence of a cluster of comets. Over time, the existence of a cometary cloud was proven, which is known today as the “Oort Cloud” and was named after the scientist who discovered it. How many comets are there? According to some assumptions, at least a trillion. The period of movement of some of these comets can be several light years. In this case, the comet will cover its entire path in 10,000,000 years!
Fragments of Comet Shoemaker-Levy 9
Reports of comets from all over the world help in their research. Astronomers could observe a very interesting and impressive vision in 1994. More than 20 fragments remaining from Comet Shoemaker-Levy 9 collided with Jupiter at crazy speed (approximately 200,000 kilometers per hour). Asteroids flew into the planet's atmosphere with flashes and huge explosions. The hot gas caused the formation of very large fire spheres. The temperature to which the chemical elements were heated was several times higher than the temperature recorded on the surface of the Sun. After which a very high column of gas could be seen through telescopes. Its height reached enormous dimensions - 3200 kilometers.
Comet Biela - a double comet
As we have already learned, there is plenty of evidence that comets break up over time. Because of this, they lose their brightness and beauty. There is only one example of such a case that can be considered - Biela's comet. It was first discovered in 1772. However, it was subsequently noticed more than once again in 1815, then in 1826 and in 1832. When it was observed in 1845, it turned out that the comet looked much larger than before. Six months later it turned out that it was not one, but two comets that were walking next to each other. What happened? Astronomers have determined that a year ago the Biela asteroid split in two. This is the last time scientists have recorded the appearance of this miracle comet. One part of it was much brighter than the other. She was never seen again. However, over time, a meteor shower, the orbit of which exactly coincided with the orbit of Comet Biela, caught the eye more than once. This incident proved that comets are capable of disintegrating over time.
What happens during a collision
For our planet, a meeting with these celestial bodies does not bode well. A large piece of comet or meteorite, approximately 100 meters in size, exploded high in the atmosphere in June 1908. As a result of this disaster, many people died reindeer and two thousand kilometers of taiga were destroyed. What would happen if such a rock exploded over a large city such as New York or Moscow? This would cost the lives of millions of people. What would happen if a comet with a diameter of several kilometers hit the Earth? As mentioned above, in mid-July 1994 it was “bombarded” with debris from comet Shoemaker-Levy 9. Millions of scientists watched what was happening. How would such a collision end for our planet?
Comets and the Earth - ideas of scientists
Information about comets known to scientists sows fear in their hearts. Astronomers and analysts paint terrible pictures in their minds with horror - a collision with a comet. When an asteroid flies into the atmosphere, it will cause irreversible destruction processes inside the cosmic body. It will explode with a deafening sound, and on Earth you can see a column of meteorite debris - dust and stones. The sky will be covered in a fiery red glow. There will be no vegetation left on Earth, since all forests, fields and meadows will be destroyed due to the explosion and fragments. Due to the fact that the atmosphere will become impenetrable to sunlight, it will become sharply cold, and plants will not be able to carry out photosynthesis. This will disrupt the nutritional cycles. sea creatures. Being without food for a long time, many of them will die. All of the above events will also affect natural cycles. Widespread acid rain will have a detrimental effect on the ozone layer, making it impossible to breathe on our planet. What happens if the comet will fall to one of the oceans? Then this can lead to disastrous environmental disasters: the formation of tornadoes and tsunamis. The only difference will be that these cataclysms will be on a much larger scale than those that we could experience in several thousand years of human history. Huge waves of hundreds or thousands of meters will sweep away everything in their path. There will be nothing left of towns and cities.
"No need to worry"
Other scientists, on the contrary, say that there is no need to worry about such cataclysms. According to them, if the Earth comes close to celestial asteroid, then this will only lead to illumination of the sky and meteor shower. Should we worry about the future of our planet? Is it likely that we will ever be met by a flying comet?
Comet fall. Should you be afraid?
Can you trust everything that scientists present? Do not forget that all the information about comets recorded above is just theoretical assumptions that cannot be verified. Of course, such fantasies can sow panic in the hearts of people, but the likelihood that something similar will ever happen on Earth is negligible. Scientists who study our solar system, admire how well thought out everything is in its design. It is difficult for meteorites and comets to reach our planet because it is protected by a giant shield. The planet Jupiter, due to its size, has enormous gravity. Therefore, it often protects our Earth from passing asteroids and comet remnants. The location of our planet leads many to believe that the entire device was thought out and designed in advance. And if this is so, and you are not a zealous atheist, then you can sleep peacefully, because the Creator will undoubtedly preserve the Earth for the purpose for which he created it.
Names of the most famous
Reports about comets from various scientists from all over the world form a huge database of information about cosmic bodies. Among the particularly well-known are several. For example, comet Churyumov - Gerasimenko. In addition, in this article we could get acquainted with comet Fumeaker-Levy 9 and comets Encke and Halley. In addition to them, comet Sadulayev is known not only to sky researchers, but also to amateurs. In this article, we tried to provide the most complete and verified information about comets, their structure and contact with other celestial bodies. However, just as it is impossible to embrace all the expanses of space, it will not be possible to describe or list all currently known comets. brief information about the comets of the Solar system is presented in the illustration below.
Sky exploration
The knowledge of scientists, of course, does not stand still. What we know now was not known to us some 100 or even 10 years ago. We can be sure that man's tireless desire to explore the vastness of space will continue to push him to try to understand the structure of celestial bodies: meteorites, comets, asteroids, planets, stars and other more powerful objects. We have now penetrated into such vastness of space that contemplating its immensity and unknowability is awe-inspiring. Many agree that all this could not have appeared on its own and without a purpose. Such a complex design must have an intention. However, many questions related to the structure of space remain unanswered. It seems that the more we learn, the more reasons we have to explore further. In fact, the more information we acquire, the more we understand that we do not know our Solar System, our Galaxy, and even more so the Universe. However, all this does not stop astronomers, and they continue to struggle with the mysteries of existence. Each comet flying nearby is of particular interest to them.
Computer program “Space Engine”
Fortunately, today not only astronomers can explore the Universe, but also ordinary people whose curiosity prompts them to do so. Not long ago, a program for computers called “Space Engine” was released. It is supported by most modern mid-range computers. It can be downloaded and installed completely free of charge using an Internet search. Thanks to this program, information about comets will also be very interesting for children. It presents a model of the entire Universe, including all comets and celestial bodies that are known to modern scientists today. To find a comet that interests us, for example, we can use the oriented search built into the system. For example, you need comet Churyumov - Gerasimenko. In order to find it, you need to enter its serial number 67 R. If you are interested in another object, for example, comet Sadulayev. Then you can try entering its name in Latin or entering its special number. Thanks to this program you can learn more about space comets.