AST 307 · Introductory Astronomy Fall 2003 Topics Chapter 20  Oct. 29, 31 What does it mean to say that a main sequence star is in both hydrostatic and thermal equilibrium? How would a star change if it radiated more energy from its surface than it generates by nuclear fusion? How does the core of a star change when all of the hydrogen at its center has been converted into helium? How does the shell around the core, where fusion of hydrogen continues, change as a result? How does the envelope, where it is too cool for fusion to occur, change? And how does the appearance of the star change? What is the next nuclear reaction to start up in the helium core of a red giant, and why do the temperature and density have to be so high before this happens? Describe the process by which a red giant becomes a planetary nebula and leaves behind a white dwarf. Describe how the pressure inside of a white dwarf differs from normal gas pressure. How can we use H-R diagrams to test the theory of stellar evolution?

29 October 2003 Astronomy Program · The University of Texas at Austin · Austin, Texas 78712 prospective student inquiries: studentinfo@astro.as.utexas.edu site comments: www@www.as.utexas.edu