Chapter 33 Winter 2011

Chapter 33 Winter 2011 - Chapter 33 History of a Star Did...

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Unformatted text preview: Chapter 33 History of a Star Did you read chap. 33? a) Yes b) No Life history of a star Humanity has not been around long enough to watch a star go through all these processes, but as we look out into the universe we can see various stars in all these stages of their life cycles, and can infer what happens. Fundamental principles that govern the life cycle of a star: 1. The law of gravitational interaction 2. The law of electromagnetic interaction 3. The strong interaction 4. The conservation of mass-energy Key to understanding s Gravitational force pulls material in • amount of mass is important s Electromagnetic, nuclear forces push material out (“gas pressure”) • type of reaction/energy determines how much push s Balance determines condition of star Beginnings s Space is mostly empty • About 1 atom/ m 3 s Matter denser in galaxies toms per m the interstellar regions much better • 10 6 atoms per m 3 in the interstellar regions (much better vacuum than we can achieve on earth, however) The Eagle Nebula Incubation period s Cold dense pockets of gas are called d a r k n e b u l a . ockets where matter is s Pockets where matter is more dense give rise to a group or cluster of p r o t o s t a r s . ( red arrows ) s Light from protostars creates e m i s s i o n n e b u l a A Stellar Nursery: Horsehead Nebula Protostar Cycling: balance between gravity and gas pressure s Rising temperature inside protostar causes gas to push back against gravity. s The collapse slows. s Radiation escapes, pressure ecreases, collapse begins again. decreases, collapse begins again. s Slow cycles continue for ~10 M years. s The protostar shines by: Gravitational Gravitational potential potential energy energy Thermal, Thermal, kinetic kinetic energy energy Light Light energy energy A plasma (ionized gas) is created when protostar gets hot enough Energy is given off when A. Elements lighter than iron fuse....
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This note was uploaded on 11/30/2011 for the course PHY S 100 taught by Professor Staff during the Winter '08 term at BYU.

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Chapter 33 Winter 2011 - Chapter 33 History of a Star Did...

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