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суперстрой екатеринбург каталог товаров и цены 2016, Nebula, Nebula - Wikipedia, What Is a Nebula? | NASA Space Place – NASA Science for Kids, Nebula | Definition, Types, Size, & Facts | Britannica, Nebula: Definition, location and variants - Space, Nebula – Definition, Examples, Types, Facts - Science Notes and Projects, What is a Nebula? Each Type & Example Photos - AstroBackyard.
nebula, any of the various tenuous clouds of and dust that occur in interstellar space. The term was formerly applied to any object outside the that had a diffuse appearance rather than a pointlike image, as in the case of a . This definition, adopted at a time when very distant objects could not be resolved into great detail, unfortunately includes two unrelated classes of objects: the extragalactic nebulae, now called , which are enormous collections of stars and gas, and the galactic nebulae, which are composed of the (the gas between the stars, with its accompanying small solid particles) within a single galaxy. Today the term nebula generally refers exclusively to the .In a the interstellar medium makes up 3 to 5 percent of the galaxy’s mass, but within a its mass fraction increases to about 20 percent. About 1 percent of the mass of the interstellar medium is in the form of “dust”—small solid particles that are efficient in absorbing and scattering radiation. Much of the rest of the mass within a galaxy is concentrated in visible stars, but there is also some form of that accounts for a substantial fraction of the mass in the outer regions.The most conspicuous property of interstellar gas is its clumpy distribution on all size scales observed, from the size of the entire (about 1020 metres, or hundreds of thousands of ) down to the distance from to the (about 1011 metres, or a few light-minutes). The large-scale variations are seen by direct observation, and the small-scale variations are observed by fluctuations in the intensity of waves, similar to the “twinkling” of starlight caused by unsteadiness in Earth’s . Various regions exhibit an enormous range of densities and temperatures. Within the Galaxy’s spiral arms about half the mass of the interstellar medium is concentrated in molecular clouds, in which occurs in molecular form (H2) and temperatures are as low as 10 kelvins (K). These clouds are inconspicuous optically and are detected principally by their (CO) emissions in the millimetre wavelength range. Their densities in the regions studied by CO emissions are typically 1,000 H2 molecules per cubic cm. At the other extreme is the gas between the clouds, with a temperature of 10 million K and a density of only 0.001 H+ per cubic cm. Such gas is produced by , the violent explosions of unstable stars.This article surveys the basic varieties of galactic nebulae distinguished by astronomers and their chemical composition and physical properties. Classes of nebulae All nebulae observed in the are forms of interstellar matter—namely, the gas between the that is almost always accompanied by solid grains of cosmic dust. Their appearance differs widely, depending not only on the temperature and density of the material observed but also on how the material is spatially situated with respect to the observer. Their chemical composition, however, is fairly uniform; it corresponds to the composition of the in general in that approximately 90 percent of the constituent are and nearly all the rest are , with , , , , and the other elements together making up about two atoms per thousand. On the basis of appearance, nebulae can be divided into two broad classes: and bright nebulae. Dark nebulae appear as irregularly shaped black patches in the sky and blot out the light of the stars that lie beyond them. Bright nebulae appear as faintly luminous glowing surfaces; they either emit their own light or reflect the light of nearby stars., Nebula’s ownership model empowers creators to sustain their work financially and encourages innovation and creativity, without the constraints imposed by profit-driven external stakeholders. See all Nebula creators. Why Subscribe? Nebula is the home of exclusive originals, bonus material, and early releases from the best independent creators. , The Westbrook Nebula, a protoplanetary nebula. A protoplanetary nebula or preplanetary nebula [27] (PPN, plural PPNe) is an astronomical object which is at the short-lived episode during a star's rapid evolution between the late asymptotic giant branch (LAGB) phase and the subsequent planetary nebula (PN) phase..
A nebula is a giant cloud of dust and gas in space. Some nebulae (more than one nebula) come from the gas and dust thrown out by the explosion of a dying star, such as a supernova. Other nebulae are regions where new stars are beginning to form. For this reason, some nebulae are called "star nurseries.", nebula, any of the various tenuous clouds of gas and dust that occur in interstellar space. The term was formerly applied to any object outside the solar system that had a diffuse appearance rather than a pointlike image, as in the case of a star.This definition, adopted at a time when very distant objects could not be resolved into great detail, unfortunately includes two unrelated classes of , Nebula play a key role in the life cycle of stars, both at their birth and death. Stars are born in dense clumps of gas, dust, and other material inside diffuse emission nebulae, also frequently , The Closest Nebula: The closest nebula to Earth is the Helix Nebula, a planetary nebula located about 700 light-years away in the constellation Aquarius. It’s often called the “Eye of God” due to its striking resemblance to a giant eye in space. Nebula Density: You can’t hide a spaceship inside a nebula! Despite their appearance , The Rosette Nebula (Emission Nebula) The Four Main Types of Nebulae Emission Nebula / Star-Forming Region. Also known as “stellar nurseries”, these massive collections of hydrogen gas are pulled together by gravity to form incredible formations like the “ Pillars of Creation ” found within the Eagle Nebula. In these star-forming regions, the formations of gas, dust, and other materials , Nebula space exists in vast expanses throughout the universe. Intense star formation occurs in nebula space, contributing to galaxy evolution. Astronomers observe nebulae in various wavelengths of light, including visible, infrared, and radio. Nebula definition describes vast, interstellar clouds of gas and dust..