AST- 105 1st EditionLecture 15Outline of Last LectureI. Star FormationII. Cloud CollapseIII. ProtostarsIV. Stellar EvolutionOutline of Current Lecture I. Reflection NebulaeII. Interstellar ReddeningIII. The Evolution of a 1 M ʘ StarIV. The Process of Main Sequence Evolution Current Lecture I. Reflection Nebulaea. Reflection Nebulae- a bluish haze seen around hot, young stars.i. Reflection Nebulae is due to interstellar dust.1. Interstellar dust reflects blue light more effectively that red light.2. A blue haze is reflected in star light.3. Stars behind interstellar dust appear redder than their true color.II. Interstellar Reddeninga. Interstellar Reddening- dust clouds between star and observer scatter more blue light that red light out of a beam.i. Stars appear redder than their true color.b. The Earth’s blue sky contains air molecules that reflect more blue light than red light. i. Therefore, the sky is lit mostly by blue reflected sunlight.ii. The Sun looks red when it is near the horizon because by then, red light has been removed and the light is traveling more through the atmospherenear the horizon.III. The Evolution of a 1 M ʘ Stara. Main sequenceb. Red giantc. Helium flashd. Horizontal branche. Second red giantf. Planetary Nebulag. White
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