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The emission line nebula and the emission nebula create their own glow. Hydrogen atoms come into activity due to the powerful ultraviolet light of the stars. The hydrogen then ionizes (loses an electron emitting a photon).
O-type stars can ionize gas within a radius of 350 light years. The M17 nebula was discovered by de Chezo in 1746 and rediscovered in 1764 by Charles Messier. It is in Sagittarius and is also called the Cygnus Nebula, Omega, Horseshoe and Lobster Nebula. Incredibly bright and its pink glow can be seen without the use of technology at low latitudes (apparent magnitude - 6). Inside are young stars that create the HII region. Ionized hydrogen is responsible for the red color.
Infrared light helps to find great amount dust, hinting at active star formation. Inside is a cluster of 30 stars, shaded by a nebula rubbing 40 light-years across. The total mass is 800 times greater than the sun.
M17 is 5500 light years away. Together with M16, it is located in one spiral arm of the Milky Way (Sagittarius-Kiel).
Nebulae in space are one of the wonders of the universe, striking in their beauty. They are valuable not only visual appeal. The study of nebulae helps scientists clarify the laws of the functioning of the cosmos and its objects, correct theories about the development of the Universe and the life cycle of stars. Today we know a lot about these objects, but far from everything.
mixture of gas and dust
Enough long time, until the middle of the century before last, nebulae were considered to be at considerable distances from us. The use of a spectroscope in 1860 made it possible to establish that many of them are composed of gas and dust. The English astronomer W. Heggins found that the light from nebulae is different from the radiation coming from ordinary stars. The spectrum of the former contains bright colored lines interspersed with dark ones, while in the latter case no such lines are observed.
Further research found that nebulae milky way and other galaxies are mostly made up of a hot mixture of gas and dust. Similar cold formations are often encountered. Such clouds of interstellar gas are also referred to as nebulae.
Classification
Depending on the properties of the elements that make up the nebula, several types of them are distinguished. All of them are presented in large numbers in the vastness of space and are equally interesting for astronomers. Nebulae that emit light for one reason or another are usually called diffuse or bright. Opposite to them in the main parameter, of course, are designated as dark. Diffuse nebulae are of three types:
reflective;
emission;
supernova remnants.
Emission nebulae, in turn, are subdivided into regions of new star formation (H II) and planetary nebulae. All of these types are characterized by certain properties that make them unique and worthy of close study.
Star formation regions
All emission nebulae are clouds of luminous gas of various shapes. Their main element is hydrogen. Under the influence of a star located in the center of the nebula, it ionizes and collides with the atoms of the heavier components of the cloud. The result of these processes is a characteristic pinkish glow.
The Eagle Nebula, or M16, is an excellent example of this type of object. Here is a region of star formation, many young, as well as massive hot stars. The Eagle Nebula is home to a well-known patch of space, the Pillars of Creation. These gas clumps, formed under the influence of the stellar wind, are the star formation zone. The formation of luminaries here is caused by the compression of gas and dust columns under the action of gravity.
Scientists have recently learned that we will only be able to admire the Pillars of Creation for another thousand years. Then they will disappear. In fact, the destruction of the Pillars occurred approximately 6,000 years ago due to a supernova explosion. However, the light from this region of space has been coming to us for about seven thousand years, so the event calculated by astronomers for us is only a matter of the future.
planetary nebulae
The name of the next type of luminous gas and dust clouds was introduced by W. Herschel. A planetary nebula is the last stage in a star's life. The shells shed by the luminary form a characteristic pattern. The nebula resembles a disk that usually surrounds a planet when viewed through a small telescope. To date, more than a thousand such objects are known.
Planetary nebulae - part of the process of transformation into At the center of formation is a hot star, similar in its spectrum to class O luminaries. Its temperature reaches 125,000 K. Planetary nebulae are mostly relatively small in size - 0.05 parsec. Most of them are located in the center of our galaxy.
The mass of the gas envelope thrown off by the star is small. It is tenths of a similar parameter of the Sun. The mixture of gas and dust is moving away from the center of the nebula at a speed of up to 20 km/s. The shell exists for about 35 thousand years, and then becomes very rarefied and indistinguishable.
Peculiarities
A planetary nebula could be various shapes. Basically, one way or another, it is close to the ball. Distinguish nebulae round, ring-shaped, similar to dumbbells, irregular shape. The spectra of such space objects include the emission lines of the luminous gas and the central star, and sometimes also the absorption lines from the spectrum of the star.
The planetary nebula radiates a huge amount of energy. It is much larger than that for the central star. The core of the formation emits ultraviolet rays due to its high temperature. They ionize gas atoms. The particles are heated, instead of ultraviolet, they begin to emit visible rays. Their spectrum contains emission lines that characterize the formation as a whole.
Nebula cat's eye
Nature is a master at creating unexpected and beautiful forms. Noteworthy in this respect is the planetary nebula, because of the similarity called the Cat's Eye (NGC 6543). It was discovered in 1786 and was the first to be identified by scientists as a cloud of luminous gas. The Cat's Eye Nebula is located in and has a very interesting complex structure.
It was formed about 100 years ago. Then the central star shed its shells and formed concentric lines of gas and dust, characteristic of the pattern of the object. To date, the mechanism of formation of the most expressive central structure of the nebula remains unclear. The appearance of such a pattern is well explained by the location of a double star in the core of the nebula. So far, however, there is no evidence to support this state of affairs.
The temperature of the halo of NGC 6543 is approximately 15,000 K. The core of the nebula is heated to 80,000 K. At the same time, the central star is several thousand times brighter than the Sun.
colossal explosion
Massive stars often end their life cycle impressive special effects. Huge in their power explosions lead to the loss of all external shells by the luminary. They move away from the center at a speed exceeding 10,000 km/s. The collision of a moving substance with a static one causes strong rise gas temperature. As a result, its particles begin to glow. Often, supernova remnants are not spherical formations, which seems logical, but nebulae of various shapes. This happens because the substance ejected at high speed unevenly forms clots and accumulations.
Traces of a thousand years ago
Perhaps the most famous supernova remnant is the Crab Nebula. The star that gave birth to her exploded almost a thousand years ago, in 1054. The exact date was established according to the Chinese chronicles, where its flash in the sky is well described.
The characteristic pattern of the crab nebula is gas ejected by a supernova and not yet completely mixed with interstellar matter. The object is located at a distance of 3300 light years from us and is continuously expanding at a speed of 120 km / s.
In the center, the Crab Nebula contains a supernova remnant, a neutron star, which emits streams of electrons that are sources of continuous polarized radiation.
reflective nebulae
Another type of these space objects consists of a cold mixture of gas and dust, unable to emit light on its own. Reflection nebulae glow due to nearby objects. These may be stars or similar diffuse formations. The spectrum of scattered light remains the same as that of its sources, but blue light dominates for the observer.
A very interesting nebula of this type is associated with the star Merope. A luminary from the Pleiades cluster has been destroying a passing molecular cloud for several million years. As a result of the influence of the star, the particles of the nebula line up in a certain sequence and are pulled towards it. After some time (the exact time is unknown), Merope can completely destroy the cloud.
A dark horse
Diffuse formations are often contrasted with an absorbing nebula. The galaxy has many of them. These are very dense clouds of dust and gas that absorb light from the emission and reflection nebulae and stars behind them. These cold cosmic formations are mainly composed of hydrogen atoms, although heavier elements are also found in them.
A magnificent representative of this type is the nebula. It is located in the constellation Orion. The characteristic shape of the nebula, so similar to the head of a horse, was formed as a result of the influence of stellar wind and radiation. The object is clearly visible due to the fact that a bright emission formation serves as its background. At the same time, the Horsehead Nebula is only a small part of an extended absorbing cloud of dust and gas, almost invisible.
Thanks to the Hubble telescope, nebulae, including planetary ones, are familiar to a wide range of people today. Photographs of the areas of space where they are located impress to the depths of the soul and leave no one indifferent.
In addition to stars, faintly luminous small hazy spots are visible through the telescope. They are called nebulae. Some of them are quite distinct. Among them, there are a few so-called planetary nebulae. Inside each of them, in the center, there is always one very hot star. Such nebulae consist of rarefied gas, which is removed in all directions from the central star at a speed of tens of kilometers per second. If the gas envelope around the star is hollow inside, then the nebula has the form of a ring, like, for example, the nebula in the constellation Lyra. But many nebulae do not have a specific shape. They look like tufted fog, spreading in jets in different sides. These nebulae called diffuse. Several hundred are known.
The most remarkable of these is the Orion Nebula. It is visible even with a weak telescope, and sometimes with the naked eye. In this vast diffuse nebulae, as in planetary nebulae, rarefied gases glow under the influence of the light of hot stars inside nebulae. Sometimes a bright star illuminates a cloud of dust particles that meet with it, comparable in size to smoke particles. Then, through a telescope, we also see a light diffuse nebula, but no longer gas, but dust. Lots of nebulae in the 19th century opened by William Herschel and his son John, who worked, in particular, in South Africa to watch the southern sky there.
In the 20th century, many gaseous nebulae were discovered and studied in the Crimea by the Russian scientist G. A. Shain. In most cases, dust nebulae do not glow, as there are usually no stars nearby that can brightly illuminate them. These dark dusty nebulae, often with distinctly outlined edges, are found as clearings in the bright regions of the Milky Way. Such nebulae, like a horse's head (in Orion, near the light diffuse nebulae), representing accumulations of the smallest dust, absorb the light of the stars behind them
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Previously, the term "nebula" meant any static phenomenon in space that has an extended form. Then this concept was concretized, having studied the mysterious object in more detail. Let's try to figure out what a similar section of the interstellar medium is.
Nebula concept in space
A nebula is a cloud of gas that contains a huge number of stars. The radiance of these celestial bodies allows the cloud to glow in different colors. Through special telescopes, such cosmic formations look like peculiar spots with a bright base.
Some interstellar regions have fairly clear contours. Many of the known gas accumulations are a patchy fog that spreads in different directions in jets and has a diffuse form of origin.
The space that is between the stars of the nebula is not an empty substance. In a rather small amount, particles of a diverse nature are concentrated here, to which atoms of certain substances can be attributed.
Distinguish the origin of diffuse and planetary formations in space. The nature of their formation is significantly different from one another, so it is necessary to carefully understand the structure of the emergence of different nebulae. Planetary objects are the product of the activity of the main stars, and diffuse objects are the consistency after the formation of stars.
Nebulae of diffuse origin are located in the spiral arms of galaxies. Such a cosmic combination of gas and dust is in most cases associated with large-scale and cold clouds. Stars form in this region, making the diffuse nebula very bright.
Education of this kind does not have its own source of nourishment. Energetically it exists due to the stars elevated temperature that are next to it or inside it. The color of such nebulae is predominantly red. This factor is due to the fact that they contain a large number of hydrogen. Shades of green and blue indicate the presence of nitrogen, helium and some heavy metals.
In the stellar region of Orion, very small diffuse formation nebulae can be observed. These formations are very small against the background of a giant cloud, which occupies almost the entire described object. In the constellation Taurus, it is realistic to fix only a few nebulae near fairly young T-type stars. This variety indicates that there is a disk that arises around bright celestial bodies.
A planetary nebula in space is a shell, the energy of which, at the final stage of formation, is dumped by a star without hydrogen reserves in the core. After such changes, the celestial body turns into a red giant, capable of rejecting its surface layer. As a result of what happened, the inside of the object sometimes has a temperature exceeding 100 degrees Celsius. As a result, the star is deformed in such a way that it becomes a white dwarf without a source of energy and heat.
In the 1920s, the definitions of "nebula" and "galaxy" were separated. The separation that occurred is seen in the example of the formation in the region of Andromeda, which is a vast galaxy of a trillion stars.
The main types of nebulae
Space education is classified according to different parameters. There are such types of nebulae: reflection, dark, emission, planetary gas accumulations and the residual product after the activity of supernovae. The division also concerns the composition of nebulae: there is gas and dust cosmic matter. First of all, attention is paid to the ability to absorb or scatter light by such objects.
dark nebula
Dark nebulae are rather dense compounds of interstellar gas and dust, the structure of which is opaque due to dust impact. Against the background of the Milky Way, clusters of this kind can occasionally be observed.
The study of such objects depends on the AV index. If the data is quite high, then the experiments are carried out exclusively with the help of submillimeter and radio wave astronomy technologies.
An example of such a formation is the Horse Head, formed in the constellation of Orion.
Such concentrations scatter the light carried by nearby stars. This object is not a source of radiation, but only reflects the radiance.
A gas-dust cloud of this type depends on the location of the stars. At close distances, there is a loss of interstellar hydrogen, which leads to an energy supply due to scattered galactic dust. Pleiades Cluster - the best sample described cosmic phenomenon. In most cases, such gas-dust clumps are located not far from the Milky Way.
Light nebulae have the following subspecies:
- cometary. The variable star underlies this formation. It illuminates the described section of the interstellar medium, but has a varying brightness. The sizes of objects are calculated in hundreds of parsecs, which indicates the possibility of a detailed study of such a concentration of gas and dust in space.
- light echo. This phenomenon is quite rare and has been studied since the beginning of the last century. The constellation Perseus after the outbreak of a supernova in 2001 made it possible to observe a similar change in the cosmic sphere. Outbursts of great intensity activated the dust, which formed a moderate type nebula for several years.
- Reflective substance with fibrous structure. Hundreds or thousands of parsecs are the sizes of this variety. Forces magnetic field star clusters move apart under external pressure, after which gas-dust objects are introduced into these fields and a kind of shell thread is formed.
gas nebula
Similar manifestations of space activity have different shape, and their types can be designated as follows:
- Planetary substances in the form of a ring. AT this case there is such a type of nebula as planetary. The layout of its components is very simple: the main star is visible in the center, around which all external changes take place.
- Fibers of gas that release their energy separately. These luminous gas substances are formed in the most unexpected way in the form of scattered sparkling weaves of gas.
- crab nebula. It is the residual phenomena after the explosion of a star of a new format. Such an event was recorded in the study of celestial bodies, which reflect their energy. At the very center of the cluster is a pulsating neutron star, which, by some measures, is one of the most productive sources of galactic energy.
dust nebula
This type of nebula looks like a kind of dip, which stands out against the background of a light cosmic clot. This fragment can be observed in the constellation of Orion, where a similar plume divides a single cloud into two clear zones. Against the background of the Milky Way, there are also dust patches that are pronounced in the region of Ophiuchi (the Serpent Nebula).
It is realistic to study such dust accumulation only with the help of a telescope of rather high power (diametrically from 150 mm). If the dusty nebula is located near a bright star, then it begins to reflect the light of this celestial body and becomes visible. Only in special images will it be possible to see this ability, which is close to diffuse nebulae.
The main indicator of such a cosmic cloud is its high temperature. It consists of ionized gas, which is formed due to the activity of the closest hot star. Its influence lies in the fact that it activates and illuminates the atoms of the nebula with the help of ultraviolet radiation.
The phenomenon is interesting because, according to the principle of education and visual indicators, it resembles neon light. As a rule, objects of the emission type have a red color due to the large accumulation of hydrogen in their composition. There may be additional tones in the form of green and blue, which were formed due to the atoms of other substances. The most striking example of such a star cluster is the famous Orion Nebula.
The most famous nebulae
The most popular in terms of study are the following nebulae: Orion, Triple Nebula, Ring and Dumbbell.
Orion Nebula
Such a phenomenon is remarkable in that it can be observed even with the naked eye. The Orion Nebula is classified as an emission type formation, which is located below the belt part of Orion.
The area of the cloud is impressive because it is almost four times the size of the moon at full phase. In the northeastern part is a dark dust cluster, which is cataloged under the name M43.
In the cloud itself there are almost seven hundred stars, which are on this moment are still being formed. The diffuse nature of the formation of the Orion Nebula makes the object very bright and colorful. Red areas indicate the presence of hot hydrogen, while blue areas indicate the presence of dust reflecting the radiance of bluish hot stars.
M42 is the closest place to Earth where stars form. Such a cradle of celestial objects is located at a distance of one and a half thousand light years from our planet and delights outside observers.
Trifid Nebula
The Triple Nebula is located in the constellation Sagittarius and looks like three separated petals. It is difficult to accurately calculate the distance from the Earth to the cloud, but scientists are guided by the parameters of two to nine thousand light years.
The uniqueness of this formation lies in the fact that it is represented by three types of nebulae at once: dark, light and emission.
M20 is the cradle for the development of young stars. Such large celestial bodies are predominantly blue in color, which was formed due to the ionization of gas accumulated in that area. When observing with a telescope, two things immediately catch the eye. bright stars right in the center of the nebula.
Upon closer examination, it becomes clear that the object seems to be torn into two parts by a black hole. A crossbar can then be seen above this gap, which gives the nebula the shape of three petals.
Ring
The ring, located in the constellation Lyra, is one of the most famous planetary substances. It is located at a distance of two thousand light years from our planet and is considered a fairly recognizable cosmic cloud.
The Ring glows due to the presence of a nearby white dwarf, and the gases included in its composition act as the remnants of the ejected consistency of the central star. The inner part of the cloud flickers greenish, which is explained by the presence of emission lines in that area. They were formed after the double ionization of oxygen, which led to the formation of a similar shade.
The central star was originally a red giant, but later turned into a white dwarf. It is realistic to consider it only in powerful telescopes, because the dimensions are extremely small. Thanks to the activity of this celestial body, the Ring Nebula arose, which envelops the central source of energy in the form of a slightly elongated circle.
The ring is one of the most popular objects of observation both among scientists and ordinary space lovers. This interest is due to the excellent visibility of the cloud at any time of the year and even in urban lighting conditions.
Dumbbell
This cloud is the territory between the stars of planetary origin, which is located in the constellation Vulpecula. Dumbbell is located at a distance of about 1200 light years from Earth and is considered a very popular object for amateur study.
Even with binoculars, the formation can be easily recognized if you focus on the constellation Arrows in the northern hemisphere of the starry sky.
The shape of M27 is very unusual and looks like a dumbbell, which is why the cloud got its name. It is sometimes referred to as a "core" because the outline of the nebula looks like a bitten apple. Through the gaseous structure of the Dumbbell, several stars are visible, and when using a powerful telescope, you can see small "ears" in the bright part of the object.
The study of the nebula in the constellation Vulpecula has not yet been completed and suggests many discoveries in this direction.
There is a rather bold hypothesis that gas-dust nebulae can influence human consciousness. Pavel Globa believes that such formations can completely change the lives of some people. According to experts in the field of astrology, nebulae have a destructive effect on the senses and change the consciousness of the inhabitants of the Earth. Star clusters, according to this version, are able to control the duration of human existence, shortening the life cycle or making it longer. It is believed that nebulae affect people more than stars. Famous astrologers explain all this by the fact that there is a certain program for which a certain cosmic cloud is responsible. Its mechanism begins to act instantly, and a person is not able to influence this.
What the nebula looks like - look at the video:
Nebulae are a magnificent phenomenon of extraterrestrial origin that needs to be studied in detail. But it is difficult to judge the reliability of the voiced assumption about the influence of star clusters on human consciousness!
Ever since Hubble gave mankind the opportunity to see with their own eyes magnificent images of deep space, a real phantasmagoria has opened up before us. Through the ultraviolet and infrared filters of the apparatus, the Universe sparkled with gems - and began to reveal its mysteries to astronomers. Scientists seem to have finally found a time machine - after all, the light of distant stars reaches the Earth for millions of years, and looking into the night sky, we see ancient other worlds, long-extinguished stars and supernovae, which in reality have already reached “age”. Star nebulae are perhaps the most beautiful and exciting cosmic objects, the essence of which has long remained incomprehensible to people. But today there is a more or less clear classification of these "eternal" substances - like people, stars are born from this dust and become it again at the end of their evolution.
Discovery history
Andromeda
What is a nebula? Previously, when the ability to look closely at the depths of space was limited, "nebulae" were called almost everything that did not have clear outlines, glowed and was relatively motionless. Therefore, the nearest colossal spiral galaxy M31 (NGC 224) was mistakenly named the Andromeda Nebula (pictured). The Hercules Cluster, which is actually a globular star cluster, was recorded in the same category. However, these mistakes should really be excused - after all, research was carried out back in 1787 by Charles Monsieur, who was searching for comets. It was then that his attention was riveted by motionless celestial bodies.
With the advent of the Lundmark apparatus, it was possible to make more precise analysis their nature: separated galaxies from nebulae, discovered non-luminous star clouds, and identified several reasons why all other clusters glow. However, not all misconceptions were corrected: at the beginning of the 20th century, it was believed that nebulae were either dusty or gaseous - therefore, the well-known researcher B.A. Vorontsov-Velyaminov placed them in different sections of his books. Modern scientists no longer doubt that any such accumulation of interstellar matter contains both dust and gas - the differences can only be in percentage terms. And now more about the "jewels" of space.
dark nebulae
horse head
Not surprisingly, their existence was not suspected for a long time - as in the case of black holes, it's like looking for a black cat in dark room. However, such objects can be considered if they are located in a well-lit area - among star clusters. good examples such objects are the "Coal Sack" or "Horse's Head" nebulae (pictured).
When the resolution of telescopes made it possible to peer into the Milky Way, astronomers initially decided that dark spots were some kind of gaps through which more distant regions of the galaxy were visible. But, as it turned out, the "sieve" theory turned out to be erroneous: black spots are concentrated dust clouds that absorb radiation and obscure the center of the Galaxy from our eyes. Being on its very outskirts, due to dark nebulae, we are deprived of the opportunity to see a kaleidoscope in the night sky, which could even outshine the light of the moon. But do not rush to be sad: it is in the heart of the Milky Way that highly radioactive stars are burning, making life on them impossible. And our ozone ball has enough work with solar hyperactivity - so for the entire biosphere as a whole, such an alignment is most welcome.
reflection nebulae
Pleiades
In order to glow, as stars do, a thermonuclear process is necessary - this, of course, does not apply to nebulae. But some of the dust clusters can reflect light, such as satellites of planets. Large stars become the source of light, and you can understand that you have a nebula of this type in front of you by the blue or blue glow around colossal suns (for example, near the stars of the Pleiades). However, there is an exception to this rule - the red supergiant Antares is surrounded by a nebula of the same color.
Ionized Nebulae
Orion
The reason for the glow of the gas is the same as for the glow of the "tail" of a comet: receiving a certain "charge" from more powerful sources, the nebulae then give it to the surrounding space. Such stellar clouds are also called emission clouds. Nebulae cannot compare with large stars - their photons have a much lower charge, and it is more difficult for them to reach the Earth - therefore we see them in the red spectrum, like the last rays of sunset. However, there are exceptions here too - in the case of a very powerful radiation source, the emission nebulae are still green and blue. Ionized clouds include, for example, the Orion Nebula (pictured), " North America”, “Tarantula”, “Pelican” and others.
planetary nebulae
cat eye
This is a type of emission nebula: usually such objects are relatively small and have a clear shape, sometimes resembling frozen circles on the water, formed from the fall of a drop. In fact, the “pension” of a giant star looks so luxurious (at least from afar): consuming the remaining hydrogen, it expands due to the shedding of its shell. Enveloping vast spaces around, these substances are influenced by the radiation of the star's core. The most incredible picture of such a process was obtained in the constellation Draco - this is the Cat's Eye Nebula. Its fibrous structure, like all other nebulae, is associated with the action of powerful magnetic fields of stars, which have certain lines of force and impede the transverse movement of electrically charged particles of dust and gas.
Nebulae from shock waves
crab nebula
The sources of such waves, which can lead to supersonic motion of matter in the interstellar medium, are the stellar wind or supernova explosions. The temperature of the resulting nebulae can reach billions of degrees, so the heated gas has radiation for the most part in the x-ray range. However, the kinetic energy of moving matter soon exhausts itself, so short-lived nebulae disappear after a short (by cosmic standards) period of time. The most famous nebula of this type is the Crab Nebula in the constellation Taurus, which appeared in the sky in 1054.
