Content of the region between the stars, including vast, diffuse clouds of gases and minute solid particles. Such tenuous matter in the Milky Way Galaxy accounts for about 5percnt of its total mass. By no means a complete vacuum, the interstellar medium contains mainly hydrogen gas, with a smaller amount of helium and sizable quantities of dust particles of uncertain composition. Primary cosmic rays also travel through interstellar space, and magnetic fields extend across much of it. Most interstellar matter occurs in cloudlike concentrations, which can condense to form stars. Stars, in turn, continually lose mass through stellar winds (see solar wind). Supernovas and planetary nebulae also feed mass back to the interstellar medium, where it mixes with matter that has not yet formed stars (see Populations I and II).
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The supernova origin of interstellar dust: interstellar dust grains are prevalent in the universe, but their origin is unclear. Massive stellar explosions may be the most important source of such dust grains.(ASTRONOMY)
Jul 14, 2006; Interstellar dust grains are prevalent in almost any astrophysical environment, and manifest their existence in many...