Molecular clouds (molecular cloud)

Molecular clouds (molecular cloud) is an interstellar cloud, its density and size allow molecules ─ ─ the most common of which is the formation of hydrogen molecule (H2) ─ ─. Its density is high enough to produce molecules can begin. Molecular clouds usually only emit electromagnetic radiation at radio wavelengths, the discovery and study of the molecular cloud are also in the band.
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Molecular cloudThe process of star formationPhysical propertiesAppeared spacesMolecular cloud type of giant molecular clouds (GMCs)Small molecular cloudHigh galactic latitude diffuse molecular clouds.Expand the molecular cloudThe process of star formationPhysical propertiesAppeared spacesMolecular cloud type of giant molecular clouds (GMCs)Small molecular cloudHigh galactic latitude diffuse molecular clouds.Expand edit this paragraph molecular cloudIt is the gathering area of ​​interstellar molecules. The observations show that, although some interstellar molecules, such as CO, almost scattered in the sky, but most of the interstellar molecules assembled into a group, the formation of molecular clouds. Molecular cloud is usually dark, invisible at optical wavelengths, temperatures typical value is 20K, the molecule an average density of 102 to 104 cm 3, the density of the central molecule cm 3 up to 106, the quality is generally 104 to 107 the mass of the sun, clouds with enough dust shield ultraviolet starlight, the molecules from destruction. A giant molecular cloud behind the Orion Nebula, it is one of the molecular clouds closest to the sun, by the small, dense core and extended low-density cloud is composed of two parts. The diameter of the former is a gap of 0.15 seconds, a density of 105 molecules cm 3, the mass 5 of mass of the sun; latter diameter of at least 10 seconds behind the great density of 103 molecules cm 3, the quality of the mass of the sun 104. Is considered to be the stars being formed BN celestial bodies in the middle of the Orion molecular cloud the BN Astrometry near another infrared source, may also include young stars are forming stars. Edit this paragraph the process of star formationAs far as we know, in the current universe, the newly formed stars are totally in the molecular cloud produced, under low-temperature and high-pressure natural result can lead to gravitational collapse beyond resist the collapse of the internal pressure. The observational evidence also shows that huge, being formed stellar cloud in large part by their own gravitational binding (as in the stars, planets and galaxies), but not bound by external pressure (like clouds in the Earth's atmosphere) . This evidence comes from the turbulent velocity and orbital velocity inferred from the carbon monoxide (CO) line width is proportional to (virial theorem).Physical propertiesThe physical properties of the molecular cloud is difficult to understand, and still controversial, their internal movement is controlled by the cold and magnetized gas turbulence. Massive molecular cloud turbulence movement far more than the speed of sound, but compared with the speed of the magnetic field disturbances. This state will lose energy quickly, than will the overall collapse is to have a stable energy reinfusion. Before star formation in molecular clouds most of the quality, they will also be some process of the collapse ─ ─ the most massive stars. Molecular clouds, especially the giant molecular clouds are usually the source of astrophysical maser (astronomical masers). Edit this paragraph appear place in our own Milky Way galaxy, molecular gas in the interstellar medium, accounting for less than one percent of the volume, but it still is the most densely within the orbits of the sun around the galactic center, and occupies about half the mass of the gas . Most of these molecular gas in the annular region of 3.5 to 7.5 thousand parsecs from the galactic center (the sun from the center is about 850 one thousand seconds gap). Carbon monoxide into the large-scale galaxy diagram related to the position of this gas and the spiral arms of the galaxy. The molecular gas in the spiral arms, indicating that the molecular cloud formation and dissipation time should be less than a thousand of years, because it is a substance through the jib to spend time. Molecular gas is located in the thickness of about 50-75 seconds gap narrow galactic plane middle, compared to the same warm cloud of atoms belonging to the ISM (of Z = 130-400pc) and the hot ionized gas in the vertical direction (Z = 1000pc) thin many. [5] in the spatial distribution of the ionized gas, the distribution of the HII region is an exception. HII regions in the molecular cloud by the intense radiation of young, massive stars inspire the the thermionic bubble formation, similar to the thickness of the molecular gas distribution in the vertical direction. On the large-scale distribution of molecular gas is smooth, but on a small scale distribution is very irregular, mostly concentrated in isolated molecular clouds and molecular cloud complex being. Edit this paragraph molecular cloud type giant molecular clouds (GMCs)Giant molecular cloud is a collection of a large number of molecular gas quality between 104-106 times the mass of the Sun. The nebula's diameter can reach dozens of parsecs, density in 102-103 particles per cubic centimeter (near the sun is an average per cubic centimeter of a particle). Secondary structures within these clouds have complex forms, including filaments, in the form of flakes, bubbles and irregular clumps. The highest density of filaments and clumps part called "molecular cloud cores, the highest density of molecular cloud cores, known as" dense molecular cloud cores, the density can be as high as 104-106 particles per cubic centimeter. Observations can with carbon monoxide search molecular cloud cores using ammonia Search dense molecular cloud cores. Concentrated in the molecular cloud of nuclear dust will block background starlight, caused by the effect of interstellar extinction formation of dark nebulae. Our "local" giant molecular clouds usually occupies a significant position in the constellation of the sky in their often constellation named, such as the Orion Molecular Cloud (OMC) or the Taurus Molecular Cloud (TMC). These molecular clouds around the sun into a circular array, called Gould tape. The quality largest molecular clouds in the Milky Way is Sagittarius B2 120 parsecs from the galactic center, forming a ring. The Sagittarius region contains abundant chemical element, is a good specimen of astronomers find new molecules in interstellar space.Small molecular cloudIsolated, gravitationally bound, quality small following in the hundreds of solar masses of molecular cloud known as Bok globule. In such a small molecular cloud in the highest density regions with nuclear equivalent of giant molecular clouds in the molecular cloud, so common among the same study.High galactic latitude diffuse molecular clouds.In 1984, the Infrared Astronomical Satellite, IRAS (IRAS) Identified a new type of diffuse molecular clouds. Dispersion into filamentous cloud at high galactic latitude regions (left the Galactic disk space) can be observed, the clouds in about 30 particles per cubic centimeter sub