Since Hubble gave humanity the opportunity to see with our own eyes magnificent photographs of deep space, a real phantasmagoria has opened up before us. Through the ultraviolet and infrared filters of the device, the Universe sparkled with gems - and began to reveal its mysteries to astronomers. It’s as if scientists have finally found a time machine - after all, the light of distant stars takes millions of years to reach the Earth, and looking into the night sky, we see ancient other worlds, long-extinct stars and supernovae, which in fact have already reached “coming of age.” Stellar nebulae are perhaps the most beautiful and exciting space objects, the essence of which remained incomprehensible to people for a long time. But today there is a more or less clear classification of these “eternal” substances - like people, stars are born from this dust and become dust again at the end of their evolution.
History of discoveries
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 called the Andromeda Nebula (pictured). The Hercules Cluster, which is actually a globular star cluster, was included in the same category. However, these errors really should be excused - after all, the research was carried out back in 1787 by Charles Monsieur, who was searching for comets. It was then that his attention was drawn to the motionless celestial bodies.
With the advent of the Lundmark apparatus, it was possible to make a more accurate analysis of their nature: they 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 famous researcher B.A. Vorontsov-Velyaminov placed them in different sections of his books. Modern scientists no longer doubt that any such cluster of interstellar matter contains both dust and gas - the differences can only be in percentage. And now more about the “jewels” of space.
Dark nebulae
horse head
It is not surprising that for a long time their existence was not suspected - as in the case of black holes, it is like looking for a black cat in a dark room. However, such objects can be seen if they are located in a well-illuminated area - among star clusters. Good examples of such objects are the Coalsack or Horsehead nebulae (pictured).
When the resolution of telescopes made it possible to peer into the Milky Way, astronomers initially decided that the dark spots were a kind of gap through which more distant regions of the galaxy were visible. But, as it turned out, the “sieve” theory turned out to be erroneous: the black spots are concentrated dust clouds that absorb radiation and obscure the center of the Galaxy from our view. Being on its very outskirts, due to dark nebulae, we are unable to see the 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 burn, making life on them impossible. And our ozone ball has enough work to do with solar hyperactivity - so for the entire biosphere as a whole, such a situation could not be more convenient.
Reflection nebulae
Pleiades
To glow, as stars do, a thermonuclear process is necessary - this, of course, has nothing to do with nebulae. But some of the dust clusters can reflect light, such as the satellites of planets. Large stars become the source of light, and you can understand that this is the type of nebula in front of you by the blue or blue glow around colossal suns (for example, near the Pleiades stars). 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 gas is the same as when the “tail” of a comet glows: receiving a certain “charge” from more powerful sources, the nebulae then release it into the surrounding space. Such stellar clouds are also called emission clouds. Nebulae cannot compare with large stars - their photons have a much smaller charge, and it is more difficult for them to reach the Earth - so we see them in the red spectrum, like the last rays of the sunset. However, there are exceptions here too - in the case of a very powerful radiation source, 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's eye
This is a type of emission nebula: usually such objects are relatively small and have a clear shape, sometimes resembling frozen circles on water formed by the flow of a drop. In fact, the “retirement” of a giant star looks so luxurious (at least from afar): using up the remaining hydrogen, it expands due to the shedding of its envelope. Enveloping vast spaces around, these substances are influenced by the radiation from the star’s core. The most incredible image of such a process was obtained in the constellation Draco - the Cat's Eye Nebula. Its fibrous structure, similar to 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, capable of leading to supersonic movement of substances in the interstellar medium, are stellar wind or supernova explosions. The resulting nebulae can reach billions of degrees in temperature, so the heated gas emits mostly 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.
In addition to the stars, faintly glowing small nebulous spots are visible through the telescope. They are called nebulae. Some of them have quite distinct outlines. 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 moves away in all directions from the central star at a speed of tens of kilometers per second. If the gas shell around the star is hollow inside, then the nebula has the appearance of a ring, such as the nebula in the constellation Lyra. But many nebulae do not have a specific shape. They look like shredded fog, spreading in streams in different directions. These nebulae are called diffuse. Several hundred of them 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 huge diffuse nebulae, as in planetary nebulae, rarefied gases glow under the influence of the light of hot stars located inside nebulae. Sometimes a bright star illuminates a cloud of dust particles that it encounters, comparable in size to smoke particles. Then through the telescope we also see a light diffuse nebula, but not a gas nebula, but a dust nebula. Many nebulae in the 19th century. discovered by William Herschel and his son John, who worked, in particular, in South Africa to observe the southern sky there.
In the 20th century, many gas nebulae were discovered and studied in Crimea by the Russian scientist G. A. Shain. In most cases, dusty nebulae do not glow, since there are usually no stars nearby that can illuminate them brightly. These dark dusty nebulae, often with clearly defined edges, are found like clearings in the light areas of the Milky Way. Such nebulae, like the Horse's Head (in Orion, near the light diffuse nebulae), representing clusters of tiny dust, absorb the light of the stars behind them
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The content of the article
NEBULA. Previously, astronomers called this any celestial objects that are stationary relative to the stars, having, in contrast to them, a diffuse, blurry appearance, like a small cloud (the Latin term used in astronomy for “nebula”) nebula means "cloud"). Over time, it became clear that some of them, such as the Orion Nebula, consist of interstellar gas and dust and belong to our Galaxy. Other “white” nebulae, like those in Andromeda and Triangulum, turned out to be giant star systems similar to the Galaxy. Here we will talk about gas nebulae.
Until the middle of the 19th century. Astronomers believed that all nebulae were distant clusters of stars. But in 1860, using a spectroscope for the first time, W. Hoggins showed that some nebulae are gaseous. When the light of an ordinary star passes through a spectroscope, a continuous spectrum is observed, in which all colors from violet to red are represented; in some places in the star’s spectrum there are narrow dark absorption lines, but they are quite difficult to notice - they are visible only in high-quality photographs of the spectra. Therefore, when observed with the eye, the spectrum of a star cluster appears as a continuous band of color. The emission spectrum of a rarefied gas, on the contrary, consists of individual bright lines, between which there is practically no light. This is exactly what Hoggins saw when observing some nebulae through a spectroscope. Later observations confirmed that many nebulae are indeed clouds of hot gas. Astronomers often call dark diffuse objects “nebulae” - also clouds of interstellar gas, but cold.
Types of nebulae.
Nebulae are divided into the following main types: diffuse nebulae, or H II regions, such as the Orion Nebula; reflection nebulae like the Merope Nebula in the Pleiades; dark nebulae like the Coalsack, which are usually associated with molecular clouds; supernova remnants like the Reticulum Nebula in Cygnus; planetary nebulae, like the Ring in Lyra.
Diffuse nebulae.
Widely known examples of diffuse nebulae are the Orion Nebula in the winter sky, as well as the Lagoon and Trifid nebulae in the summer sky. The dark lines cutting the Triple Nebula apart are the cold dust clouds lying in front of it. The distance to this nebula is approx. 2200 St. years, and its diameter is slightly less than 2 sv. years. The mass of this nebula is 100 times that of the sun. Some diffuse nebulae, such as Lagoon 30 Doradus and the Orion Nebula, are much larger and more massive.
Unlike stars, gaseous nebulae do not have their own source of energy; they glow only if there are hot stars within or nearby them with a surface temperature of 20,000–40,000 ° C. These stars emit ultraviolet radiation, which is absorbed by the gas of the nebula and re-emitted by it in the form of visible light. Passed through a spectroscope, this light is split into characteristic emission lines of various elements of the gas.
Reflection nebulae.
A reflection nebula forms when a cloud of light-scattering dust grains is illuminated by a nearby star whose temperature is not high enough to cause the gas to glow. Small reflection nebulae are sometimes visible near forming stars.
Dark nebulae.
Dark nebulae are clouds consisting mainly of gas and partly of dust (mass ratio ~ 100:1). In the optical range, they obscure the center of the Galaxy from us and are visible as black spots along the entire Milky Way, for example, the Great Divide in Cygnus. But in the infrared and radio ranges, these nebulae emit quite actively. Some of them are now forming stars. The gas density in them is much higher than in the intercloud space, and the temperature is lower, from - 260 to - 220 ° C. They mainly consist of molecular hydrogen, but other molecules are also found in them, including amino acid molecules.
Supernova remnants.
When an aged star explodes, its outer layers are shed at a speed of approx. 10,000 km/s. This fast-moving material, like a bulldozer, rakes up interstellar gas in front of it, and together they form a structure similar to the Reticulum Nebula in Cygnus. During a collision, moving and stationary substances heat up in a powerful shock wave and glow without additional energy sources. The temperature of the gas reaches hundreds of thousands of degrees, and it becomes a source of X-ray radiation. In addition, the interstellar magnetic field intensifies in the shock wave, and charged particles - protons and electrons - are accelerated to energies much higher than the energy of thermal motion. The movement of these fast charged particles in a magnetic field produces radiation in the radio range, called non-thermal.
The most interesting supernova remnant is the Crab Nebula. In it, the gas ejected by the supernova has not yet mixed with interstellar matter.
In 1054, a star flare was visible in the constellation Taurus. The picture of the outbreak, reconstructed from Chinese chronicles, shows that it was the explosion of a supernova, which at its maximum reached a luminosity 100 million times higher than the sun. The Crab Nebula is located exactly at the site of that outbreak. By measuring the angular size and rate of expansion of the nebula and dividing one by the other, they calculated when this expansion began - almost exactly the year 1054. There is no doubt: the Crab Nebula is a supernova remnant.
In the spectrum of this nebula, each line is bifurcated. It is clear that one component of the line, shifted to the blue side, comes from the part of the shell approaching us, and the other, shifted to the red side, from the part moving away. Using the Doppler formula, we calculated the expansion speed (1200 km/s) and, comparing it with the angular expansion speed, determined the distance to the Crab Nebula: approx. 3300 St. years.
The Crab Nebula has a complex structure: its outer fibrous part emits individual emission lines characteristic of hot gas; Inside this shell is an amorphous body, the radiation of which has a continuous spectrum and is highly polarized. In addition, powerful non-thermal radio emission emanates from there. This can only be explained by the fact that inside the nebula, fast electrons move in a magnetic field, emitting synchrotron radiation in a wide range of the spectrum - from radio to X-rays. For many years, the source of fast electrons in the Crab Nebula remained mysterious, until in 1968 it was possible to discover a rapidly rotating neutron star at its center - a pulsar, the remnant of a massive star that exploded about 950 years ago. Making 30 revolutions per second and possessing a huge magnetic field, the neutron star emits streams of fast electrons responsible for the observed radiation into the surrounding nebula.
It turned out that the mechanism of synchrotron radiation is very common among active astronomical objects. In our Galaxy, we can point out many supernova remnants that emit as a result of the movement of electrons in a magnetic field, for example, the powerful radio source Cassiopeia A, with which an expanding fibrous shell is associated in the optical range. From the core of the giant elliptical galaxy M 87, a thin jet of hot plasma with a magnetic field is ejected, emitting in all spectral ranges. It is unclear whether active processes in the nuclei of radio galaxies and quasars are related to supernovae, but the physical processes of radiation in them are very similar.
Planetary nebulae.
The simplest galactic nebulae are planetary. There are about two thousand of them discovered, and in total there are about two thousand of them in the Galaxy. 20,000. They are concentrated in the galactic disk, but do not gravitate, like diffuse nebulae, to the spiral arms.
When observed through a small telescope, planetary nebulae appear as blurry disks without much detail and therefore resemble planets. Many of them have a blue hot star visible near the center; a typical example is the Ring Nebula in Lyra. Like diffuse nebulae, the source of their glow is the ultraviolet radiation of the star located inside.
Spectral analysis.
To analyze the spectral composition of the nebula's emission, a slitless spectrograph is often used. In the simplest case, a concave lens is placed near the focus of the telescope, turning a converging beam of light into a parallel one. It is directed onto a prism or diffraction grating, which splits the beam into a spectrum, and then a convex lens is used to focus the light onto a photographic plate, obtaining not just one image of the object, but several, depending on the number of emission lines in its spectrum. However, the image of the central star is stretched into a line, since it has a continuous spectrum.
The spectra of gaseous nebulae contain lines of all the most important elements: hydrogen, helium, nitrogen, oxygen, neon, sulfur and argon. Moreover, as everywhere else in the Universe, hydrogen and helium turn out to be much larger than the rest.
The excitation of hydrogen and helium atoms in the nebula does not occur in the same way as in a laboratory gas-discharge tube, where a stream of fast electrons, bombarding the atoms, transfers them to a higher energy state, after which the atom returns to its normal state, emitting light. In the nebula there are no such energetic electrons that could excite an atom with their impact, i.e. “throw” its electrons into higher orbits. In the nebula, “photoionization” of atoms occurs by ultraviolet radiation from the central star, i.e. the energy of the arriving quantum is enough to completely tear off an electron from the atom and let it go into “free flight”. On average, 10 years pass until a free electron meets an ion, and they again unite (recombine) into a neutral atom, releasing binding energy in the form of light quanta. Recombination emission lines are observed in the radio, optical and infrared spectral ranges.
The strongest emission lines in planetary nebulae belong to oxygen atoms that have lost one or two electrons, as well as nitrogen, argon, sulfur and neon. Moreover, they emit lines that are never observed in their laboratory spectra, but appear only under conditions characteristic of nebulae. These lines are called "forbidden". The fact is that an atom is usually in an excited state for less than a millionth of a second, and then goes into a normal state, emitting a quantum. However, there are some energy levels between which the atom makes transitions very “reluctantly”, remaining in an excited state for seconds, minutes and even hours. During this time, under the conditions of a relatively dense laboratory gas, the atom necessarily collides with a free electron, which changes its energy, and the transition is eliminated. But in an extremely rarefied nebula, an excited atom does not collide with other particles for a long time, and, finally, a “forbidden” transition occurs. That is why forbidden lines were first discovered not by physicists in laboratories, but by astronomers observing nebulae. Since these lines were not present in the laboratory spectra, for some time it was even believed that they belonged to an element unknown on Earth. They wanted to call him “nebulium,” but the misunderstanding was soon cleared up. These lines are visible in the spectra of both planetary and diffuse nebulae. The spectra of such nebulae also contain weak continuous emission that occurs when electrons recombine with ions.
In spectrograms of nebulae obtained with a slit spectrograph, the lines often appear broken and split. This is the Doppler effect, indicating the relative motion of parts of the nebula. Planetary nebulae typically expand radially from the central star at a speed of 20–40 km/s. Supernova shells expand much faster, exciting a shock wave in front of them. In diffuse nebulae, instead of a general expansion, turbulent (chaotic) movement of individual parts is usually observed.
An important feature of some planetary nebulae is the stratification of their monochromatic radiation. For example, the emission of singly ionized atomic oxygen (which has lost one electron) is observed in a wide area, at a great distance from the central star, and doubly ionized (i.e., having lost two electrons) oxygen and neon are visible only in the inner part of the nebula, while quadruple ionized neon or oxygen are noticeable only in its central part. This fact is explained by the fact that the energetic photons necessary for stronger ionization of atoms do not reach the outer regions of the nebula, but are absorbed by the gas not far from the star.
In terms of their chemical composition, planetary nebulae are very diverse: elements synthesized in the bowels of the star, in some of them were mixed with the substance of the ejected shell, while in others they were not. The composition of supernova remnants is even more complex: the material ejected by the star is largely mixed with interstellar gas, and, in addition, different fragments of the same remnant sometimes have different chemical compositions (as in Cassiopeia A). This material is likely ejected from various depths of the star, which makes it possible to test the theory of stellar evolution and supernova explosions.
Origin of nebulae.
Diffuse and planetary nebulae have completely different origins. Diffuse ones are always found in star formation regions - usually in the spiral arms of galaxies. They are usually associated with large, cold clouds of gas and dust in which stars form. A bright diffuse nebula is a small piece of such a cloud, heated by a hot massive star born nearby. Since such stars form infrequently, diffuse nebulae do not always accompany cold clouds. For example, there are such stars in Orion, so there are several diffuse nebulae, but they are tiny compared to the invisible dark cloud that occupies almost the entire constellation of Orion. In the small star-forming region of Taurus there are no bright hot stars, and therefore no noticeable diffuse nebulae (there are only a few faint nebulae near active young T Tauri stars).
Planetary nebulae are shells shed by stars at the final stage of their evolution. A normal star shines due to thermonuclear reactions occurring in its core, converting hydrogen into helium. But when the supply of hydrogen in the star's core is depleted, rapid changes occur: the helium core contracts, the shell expands, and the star turns into a red giant. These are usually variable stars such as Mira Ceti or OH/IR with huge pulsating envelopes. Eventually they shed the outer parts of their shells. The shellless interior of the star has a very high temperature, sometimes above 100,000 ° C. It gradually contracts and turns into a white dwarf, deprived of a nuclear energy source and slowly cooling. Thus, planetary nebulae are ejected by their central stars, while diffuse nebulae such as the Orion Nebula are material that was left unused during the star formation process.
Spectral analysis. To analyze the spectral composition of the nebula's emission, a slitless spectrograph is often used. In the simplest case, a concave lens is placed near the focus of the telescope, turning a converging beam of light into a parallel one. It is directed at a prism or diffraction grating, which splits the beam into a spectrum, and then a convex lens is used to focus the light on a photographic plate, obtaining not just one image of the object, but several, depending on the number of emission lines in its spectrum. However, the image of the central star is stretched into a line, since it has a continuous spectrum.The spectra of gas nebulae contain lines of all the most important elements: hydrogen, helium, nitrogen, oxygen, neon, sulfur and argon. Moreover, as everywhere else in the Universe, hydrogen and helium turn out to be much larger than the rest.
The excitation of hydrogen and helium atoms in the nebula does not occur in the same way as in a laboratory gas-discharge tube, where a stream of fast electrons, bombarding the atoms, transfers them to a higher energy state, after which the atom returns to its normal state, emitting light. In the nebula there are no such energetic electrons that could excite an atom with their impact, i.e. “throw” its electrons into higher orbits. In the nebula, “photoionization” of atoms occurs by ultraviolet radiation from the central star, i.e. the energy of the arriving quantum is enough to completely tear off an electron from the atom and let it go into “free flight”. On average, 10 years pass until a free electron meets an ion, and they again unite (recombine) into a neutral atom, releasing binding energy in the form of light quanta. Recombination emission lines are observed in the radio, optical and infrared spectral ranges.
The strongest emission lines in planetary nebulae belong to oxygen atoms that have lost one or two electrons, as well as nitrogen, argon, sulfur and neon. Moreover, they emit lines that are never observed in their laboratory spectra, but appear only under conditions characteristic of nebulae. These lines are called "forbidden". The fact is that an atom is usually in an excited state for less than a millionth of a second, and then goes into a normal state, emitting a quantum. However, there are some energy levels between which the atom makes transitions very “reluctantly”, remaining in an excited state for seconds, minutes and even hours. During this time, under the conditions of a relatively dense laboratory gas, the atom necessarily collides with a free electron, which changes its energy, and the transition is eliminated. But in an extremely rarefied nebula, an excited atom does not collide with other particles for a long time, and finally a “forbidden” transition occurs. That is why forbidden lines were first discovered not by physicists in laboratories, but by astronomers observing nebulae. Since these lines were not present in the laboratory spectra, for some time it was even believed that they belonged to an element unknown on Earth. They wanted to call him “nebulium,” but the misunderstanding was soon cleared up. These lines are visible in the spectra of both planetary and diffuse nebulae. The spectra of such nebulae also contain weak continuous emission that occurs when electrons recombine with ions.
In spectrograms of nebulae obtained with a slit spectrograph, the lines often appear broken and split. This is the Doppler effect, indicating the relative motion of parts of the nebula. Planetary nebulae typically expand radially from the central star at a speed of 20-40 km/s. Supernova shells expand much faster, exciting a shock wave in front of them. In diffuse nebulae, instead of a general expansion, turbulent (chaotic) movement of individual parts is usually observed.
An important feature of some planetary nebulae is the stratification of their monochromatic radiation. For example, the emission of singly ionized atomic oxygen (which has lost one electron) is observed in a wide area, at a great distance from the central star, and doubly ionized (i.e., having lost two electrons) oxygen and neon are visible only in the inner part of the nebula, while quadruple ionized neon or oxygen are noticeable only in its central part. This fact is explained by the fact that the energetic photons necessary for stronger ionization of atoms do not reach the outer regions of the nebula, but are absorbed by the gas not far from the star.
In terms of their chemical composition, planetary nebulae are very diverse: elements synthesized in the bowels of the star, in some of them were mixed with the material of the ejected shell, while in others they were not. The composition of supernova remnants is even more complex: the material ejected by the star is largely mixed with interstellar gas, and, in addition, different fragments of the same remnant sometimes have different chemical compositions (as in Cassiopeia A). This material is likely ejected from various depths of the star, which makes it possible to test the theory of stellar evolution and supernova explosions.
- This types of nebulae. They are beautiful, majestic, fascinating, and despite the fact that they are difficult to detect through a telescope, observation enthusiasts devote a lot of time to searching for them. They are unique, each one is different from the other. The dimensions in space are relatively small and are located at short distances from us (from the point of view of astronomical values). They consist predominantly of hydrogen - 90% and helium - 9.9%. We will not consider whether each nebula belongs to one or another within the framework of this article; our task is different. And let me stop ranting and get straight to the point.
1. Diffuse nebula
Diffuse Lagoon Nebula
Diffuse nebulae, unlike stars, do not have their own source of energy. The glow inside them comes from hot stars that are inside or near it. Such nebulae are found to a greater extent on the “branches” of galaxies, where active star formation occurs and are matter that was not included in the composition of the star.
Diffuse nebulae are predominantly red in color - this is due to the abundance of hydrogen inside them. Green and blue colors tell us about other chemical elements such as helium, nitrogen, and heavy metals.
These nebulae include the most popular and accessible for observation with devices with low magnification - Orion Nebula in the constellation Orion, which I mentioned in the article.
Diffuse nebulae are also often called emission.
2. Reflection nebula
Witch's Head Reflection Nebula
A reflection nebula does not emit any light of its own. This is a cloud of gas and dust that reflects light from nearby stars. Just like diffuse nebulae, reflection nebulae are found in regions of active star formation. They have a bluish tint to a greater extent, because... it dissipates better than others.
Not many nebulae of this type are known today—about 500.
Some sources do not distinguish reflection nebula separately, but classify it as a diffuse nebula.
3. Dark Nebula
Dark Horsehead Nebula
Such a nebula occurs due to the blocking of light from objects located behind it. This is a cloud. The composition is almost identical to the previous reflecting nebula, differing only in the location of the light source.
As a rule, a dark nebula is observed together with a reflection or diffuse nebula. Great example in the photo above. "Horse head"— here the dark region blocks the light from a much larger diffuse nebula behind it. With an amateur telescope, such nebulae will be extremely difficult or almost impossible to see. However, in the radio range, such nebulae actively emit electromagnetic waves.
4. Planetary nebula
Planetary nebula M 57
Perhaps the most beautiful type of nebula. As a rule, such a nebula is the result of the end of a star’s life, i.e. its explosion and scattering of gas into outer space. Despite the fact that the star explodes, it is called planetary. This is due to the fact that when observed, such nebulae look like planets. Most of them are round or oval in shape. The shell of gas located inside is illuminated by the remains of the star itself.
In total, about two thousand planetary nebulae have been discovered, although in our Milky Way galaxy alone there are more than 20,000 of them.
5. Supernova Remnant
Crab Nebula M 1
Supernova- this is a sharp increase in the brightness of a star as a result of its explosion and the release of a huge amount of energy into the outer space environment.
The photo above shows an excellent example of the explosion of a star in which the ejected gas has not yet mixed with interstellar matter. Based on Chinese chronicles, this explosion was recorded in 1054. But we must understand that the distance to the Crab Nebula is about 3300 light years.
That's all. There are only 5 types of nebulae that you need to know and be able to recognize. I hope I managed to convey information to you in an accessible form and in simple language. If you have questions, ask, write in the comments. Thank you.
