AS102 Study Guide - Final Guide: Protostar
Document Summary
When we look away from earth, especially at night, we see an inky black sky dotted with stars and we could easily come to the conclusion that most of outer space is filled with nothing. Existing between the stars is a collection of low-density gas and dust known as the interstellar medium (ism). 75% hydrogen, 25% helium and traces of heavier atoms and molecules. About 1% of the ism is dust, mostly carbon and silicates (rocky substances) mixed or covered with frozen water. The ism is a varied concoction of cool, comparatively dense clouds of all shapes and sizes interspersed with hot, lower-density gaseous currents. Some ism clouds are readily visible such as the. Great nebula in orion, although you really need a telescope to see it. Some clouds dense enough that little or no visible starlight can penetrate it while others are thin enough to allow us to see the stars far behind the nebula.
