Nebulae in space - one of the wonders of the universe,striking in their beauty. They are valuable not only visual appeal. The study of nebulae helps scientists to clarify the laws of the functioning of the cosmos and its objects, to 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 all.
Mixture of gas and dust
Long enough up to the middlethe century before last, the nebulae were regarded as star clusters, which were located at considerable distances from us. The use of the spectroscope in 1860 made it possible to establish: many of them consist of gas and dust. The English astronomer William Heggins discovered that the light from the nebulae is different from the radiation coming from ordinary stars. The spectrum of the former contains bright color lines interspersed with dark ones, whereas in the second case there are no such black stripes.
Further studies have established thatNebulae of the Milky Way and other galaxies are mainly composed of a hot mixture of gas and dust. Often encountered and similar cold formations. Such clouds of interstellar gas also belong to nebulae.
Classification
Depending on the properties of the constituent nebulaelements distinguish several types of them. All of them are represented in large numbers in the vastness of space and are equally interesting for astronomers. Nebulae that emit light for one reason or another are commonly referred to as diffuse or light. Opposite to them in the main parameter, naturally, are designated as dark. Diffuse nebulae are of three types:
reflective;
emission;
supernova remnants.
Emission, in turn, are divided intothe formation of new stars (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 areas
All emission nebulae are clouds.glowing gas of different forms. The main element constituting them is hydrogen. Under the action of a star located in the center of the nebula, it is ionized 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 - magnificentrepresentative of this type of objects. Here is the region of star formation, many young, as well as massive hot luminaries. The Eagle Nebula is the place where the well-known part of the cosmos, the Pillars of Creation, is located. These gas bunches, formed under the influence of the stellar wind, are the zone of star formation. The formation of luminaries here is caused by the compression of gas and dust columns under the action of gravity.
Recently, scientists have learned that to admirePillars of creation, we can still only a thousand years. Then they disappear. In fact, the destruction of the Pillars occurred about 6,000 years ago due to a supernova explosion. However, the light from this area of space goes 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 dustClouds was introduced by W. Herschel. The planetary nebula is the last stage in the life of a star. The shells discharged by the luminary form a characteristic pattern. The nebula resembles a disk, usually surrounding a planet when viewed through a small telescope. To date, more than a thousand of such objects are known.
Planetary nebulae - part of the processtransformations of red giants into white dwarfs. In the center of the formation is a hot star, in its spectrum similar to the light bodies of class O. Its temperature reaches 125,000 K. The planetary nebulae are mostly relatively small - 0.05 parsecs. Most of them are located in the center of our galaxy.
The mass of the gas envelope, dropped by a star, is small.It is tenths of a similar parameter of the Sun. The mixture of gas and dust is removed from the center of the nebula at a speed reaching 20 km / s. The shell exists for about 35 thousand years, and then becomes highly sparse and indistinguishable.
Features
Planetary nebula can be of various shapes.Basically, anyway, it is close to the ball. Distinguish nebulae round, ring-shaped, similar to dumbbells, irregularly shaped. The spectra of such space objects include emission lines of a luminous gas and a central star, and sometimes absorption lines from the spectrum of the star.
Planetary nebula radiates enormousamount of energy. It is much larger than the central star. The core of the formation, because of its high temperature, emits ultraviolet rays. They ionize gas atoms. The particles are heated, instead of ultraviolet, they begin to emit visible rays. Their spectrum contains emission lines characterizing the formation as a whole.
Feline Nebula
Nature is an expert at creating unexpected andbeautiful forms. Notable in this regard is the planetary nebula, due to its similarity, called the Feline Eye (NGC 6543). It was discovered in 1786 and was the first that scientists identified as a cloud of luminous gas. The cat's eye nebula is located in the constellation of the Dragon and has a very interesting complex structure.
It was formed about 100 years ago.Then the central star dropped its envelopes and the concentric lines of gas and dust, characteristic of the drawing of the object, were formed. To date, the mechanism of forming the most expressive central structure of the nebula remains incomprehensible. The appearance of such a pattern is well explained by the location in the core of the nebula of a double star. However, so far there is no information testifying in favor of this state of affairs.
The halo temperature 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 lifecycle of impressive "special effects." The explosions, huge in their power, lead to the loss by the luminary of all the outer shells. They move away from the center with a speed exceeding 10,000 km / s. A collision of a moving substance with a static causes a strong increase in gas temperature. As a result, its particles begin to glow. Often, supernova remnants are not spherical formations, which seems logical, but nebulae of the most diverse forms. It happens this way because the substance thrown out at a huge speed irregularly forms bunches and clumps.
Trail of a thousand years ago
Perhaps the most famous supernova remnant iscrab nebula. The star that gave birth to it exploded almost a thousand years ago, in 1054. The exact date was established by the Chinese annals, where its flash in the sky is well described.
Characteristic drawing of a crab nebulais a gas emitted by a supernova and not yet fully 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 of the crab nebula contains a supernova remnant - a neutron star, which emits streams of electrons, which are sources of continuous polarized radiation.
Reflecting Nebulae
Another type of these space objects consists ofcold mixture of gas and dust, unable to independently emit light. Reflecting nebulae glow at the expense of nearby objects. These can be stars or similar diffuse formations. The spectrum of the scattered light remains the same as that of its sources, but the blue light in it for the observer prevails.
A very interesting nebula of this type is associated withstar merope. The light from the Pleiades cluster has been destroying a molecular cloud passing by for several million years. As a result of the star's impact, the nebula particles line up in a certain sequence and stretch toward it. After some time (the exact date is unknown) Merope can completely destroy the cloud.
A dark horse
Diffuse formations are often contrasted.absorbing nebula. The Milky Way galaxy has a lot of them. These are very dense clouds of dust and gas that absorb the light of emission and reflection nebulae behind them, as well as stars. These cold cosmic formations consist mainly of hydrogen atoms, although they also contain heavier elements.
Magnificent representative of this type -Horsehead Nebula. It is located in the constellation Orion. A nebula-like shape, so similar to a horse's head, was the result of stellar wind and radiation. The object is clearly visible due to the fact that it serves as a bright emission formation. At the same time, the Horsehead Nebula is only a small part of an extensive absorbing cloud of dust and gas, which is almost invisible.
Thanks to the Hubble Telescope, the nebulae, includingand planetary, familiar today to a wide circle of people. The photographs of the parts of the cosmos where they are located are impressive to the depths of the soul and do not leave anyone indifferent.
