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An interstellar cloud is generally an accumulation of gas, plasma, and dust in our and other galaxies. But differently, an interstellar cloud is a denser-than-average region of the interstellar medium , the matter and radiation that exists in the space between the star systems in a galaxy.
The visible-light (left) and infrared (right) views of the Trifid Nebula—a giant star-forming cloud of gas and dust located 5,400 light-years away in the constellation Sagittarius Stars are thought to form inside giant clouds of cold molecular hydrogen — giant molecular clouds roughly 300,000 times the mass of the Sun ( M ☉ ) and 20 ...
Stars form by gravitational collapse of interstellar gas clouds. As the collapse increases the density, radiative energy loss decreases due to increased opacity. This raises the temperature of the cloud which prevents further collapse, and a hydrostatic equilibrium is established. Gas continues to fall towards the core in a rotating disk.
The fragments now condense into rotating spheres of gas that serve as stellar embryos. [25] Complicating this picture of a collapsing cloud are the effects of turbulence, macroscopic flows, rotation, magnetic fields and the cloud geometry. Both rotation and magnetic fields can hinder the collapse of a cloud.
As this collapsing cloud, called a solar nebula, becomes denser, random gas motions originally present in the cloud average out in favor of the direction of the nebula's net angular momentum. Conservation of angular momentum causes the rotation to increase as the nebula radius decreases. This rotation causes the cloud to flatten out—much like ...
Map showing the Sun located near the edge of the Local Interstellar Cloud and Alpha Centauri about 4 light-years away in the neighboring G-Cloud complex Interstellar medium and astrosphere meeting. Astronomers describe the ISM as turbulent, meaning that the gas has quasi-random motions coherent over a large range of spatial scales.
Molecular clouds typically have interstellar medium densities of 10 to 30 cm-3, and constitute approximately 50% of the total interstellar gas in a galaxy. [11] Most of the gas is found in a molecular state. The visual boundaries of a molecular cloud is not where the cloud effectively ends, but where molecular gas changes to atomic gas in a ...
Some nebulae form from gas that is already in the interstellar medium while others are produced by stars. Examples of the former case are giant molecular clouds , the coldest, densest phase of interstellar gas, which can form by the cooling and condensation of more diffuse gas.