PHYS 1600 : Chapter 12
13 Dec 2011
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Document Summary
The pre-main-sequence phase is the period when the material that will form the star is organized in some way and becomes an entity, followed by a period of evolution into a star. Interstellar medium: matter (gas and dust) existing between the stars. Contains 10% of the observed mass in our galaxy. Most is too cold to be seen optically, and must be seen through infrared and radio telescopes. Composed of gas containing isolated atoms and molecules and tiny pieces of dust. 90% hydrogen, 9% helium and 1% metals (all other elements). Astronomers map out the interstellar medium to look for new stars. New stars form from this interstellar medium. (co, co2, h2o, nh3, h2co, c2h4o2). Reflection nebula: a comparatively dense cloud of gas and dust in interstellar space that is illuminated by a star between it and earth (appearing as a bluish haze). Often embedded in much larger bodies of gas and dust, called molecular clouds.
