giant molecular clouds

giant molecular clouds

(GMCs) Huge molecular clouds that are the main sites for star formation in our Galaxy and others. The average linear dimension of a GMC is about 40 parsecs, total mass about 5 × 105 solar masses, with gas temperatures of 15–30 K. GMCs are found to lie mostly in the Galactic plane. Warmer active clouds lie in the spiral arms; smaller cooler clouds are distributed almost randomly throughout the disk. It is estimated that there are between 4000 and 5000 GMCs in the Galaxy, implying a total mass of 2 × 109 solar masses. This represents a large proportion – possibly up to 50% – of the Galaxy's gas content, and is of importance in theories of galactic evolution and structure.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
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References in periodicals archive ?
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The most recent studies on the K-S law examined the index at sub-kpc scales [14-17], closing from the intrinsic scale of star formation, that is, giant molecular clouds size (GMCs) [6].
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By combining these with observations from Planck, we can now obtain a link to the large-scale structures of giant molecular clouds," remarks Timea Csengeri from the Max Planck Institute for Radio Astronomy (MPIfR), Bonn, Germany, who led the work of combining the APEX and Planck data.
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The astronomers combined data collected by the Planck space telescope to cover a larger area of the Milky Way. By combining these with observations from Planck, we can now obtain a link to the large-scale structures of giant molecular clouds," Timea Csengeri, of the Max Planck Institute for Radio Astronomy, said in a statement.
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Computational models of stars forming within galaxies commonly zoom in on giant molecular clouds in a volume of interstellar space tens of light-years across with a resolution (ability to distinguish details) smaller than the size of our solar system.
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In some regions of the Milky Way, hydrogen and other elements gravitate together to form giant molecular clouds. One of the nearest examples is the Orion Molecular Cloud, whose dark cloak of dust and gas spans 100 light-years in southern Orion.
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Papers on giant molecular clouds include a report of the Boston University-FCRAO Galactic Ring Survey.
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