The Evolution of Stars

Quick Write In this chapter, you will learn about the how stars change (evolve). Write down these questions and answer them in complete sentences. 1. What do stars begin as? 2. What is the name of the process where atoms are pressed together creating solar radiation? 3. Can stars die?

1. What does stellar evolution mean? A star’s changes during its lifetime. 2. How does a star begin? As a nebula (cloud of dust and gas). 3. Then what? Gravity causes the cloud of dust and gas to begin to condense into a smaller/denser object.

4. Is there a spin/rotation involved? Yes, there is a spin which creates a disc around a dense object. This is called a protostar.

Check for Understanding All stars begin as what? Nebula or Interstellar Cloud of Dust and Gas or Both What causes the nebula to condense into a more dense object? Mass or Gravity Movie

6. Does the star’s size change at all? Yes, it will expand and contract until hydrostatic equilibrium is reached. 7. Fusion through time? Diff. elements will be fused up to iron in stars the size of the Sun. 5. Then what? T and P become high enough for fusion of H to begin.

8. What happens when fusion stops? Outward push stops, gravity takes over, star shrinks. 9. What next? It depends on the mass of the star.

Check for Understanding What must increase within a star before fusion can begin? Temp or Pressure or Both What happens when fusion stops? Movie