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L1820GH09Stars_Star_formation

L1820GH09Stars_Star_formation - Star formation Lecture...

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March 17&19, 2009 star formation Star formation •Lecture topics: stages in star formation •Text reading: Chapter 3 – 3.4; Chapter 4 – 4.1-2
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March 17&19, 2009 star formation The physics of stars - review A star begins simply as a roughly spherical ball of (mostly) hydrogen gas, responding only to gravity and it’s own pressure. To understand how this simple system behaves, however, requires an understanding of: 1. Fluid mechanics 2. Electromagnetism 3. Thermodynamics 4. Special relativity 5. Chemistry 6. Nuclear physics 7. Quantum mechanics X-ray ultraviolet infrared radio
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March 17&19, 2009 star formation The sun as a star The sun is a “middling” star – • not the biggest or smallest • not the brightest or faintest • not the hottest or coolest • not the most massive or least massive Range of properties for normal stars: 9 radius: ~10 -2 – 10 3 R sun 9 luminosity: ~10 -4 – 10 6 L sun 9 temperature: ~3000-30000K (sun is ~6000K) 9 mass: ~0.1-50 M sun Now – a brief look at stars other than the Sun
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March 17&19, 2009 star formation The H-R Diagram Temperature (K) Luminosity (L/Lo)
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March 17&19, 2009 star formation The Hertzsprung-Russell diagram stars do not randomly populate the L,T plane •colours and luminosities of stars are strongly correlated • the Hertzsprung-Russell (1914) diagram proved to be the key that unlocked the secrets of stellar evolution • principal feature is the main sequence (dwarfs) • the brighter stars are known as giants BLUE Colour RED Luminosity
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