2.  Explain how stars form.  Explain how stars get their energy.  Give examples of why stars change over time.  Compare the evolution of medium and high mass stars.

6.  Nuclear fusion separates stars and brown dwarfs from Jupiter-like objects. Nuclear fusion is the process of light nuclei combining to form heavier nuclei. For elements lighter than iron, this process liberates energy. The fusion of elements heavier than iron takes energy rather than gives energy.

7. The helium atom that is formed has less mass then the four hydrogen atoms did separately. When the protons of the hydrogen atoms are forced together the extra mass is released... as energy! Typically this amounts to about 0.7% of the total mass, converted to an amount of energy predictable using the formula.

9. This is the state our sun is in!

14. *Electrons of atoms are pushed close to the nucleus *Central core extremely small and dense. *One spoonful = several tons.

15. *Star has completely burned out. This is the last stage in the life of a medium mass star.

23. http://www.phschool.com/webcodes10/index.c fm?wcprefix=czp&wcsuffix=7252&fuseaction= home.gotoWebCode&x=11&y=8

24. Explain how stars form. Explain how stars get their energy. Give examples of why stars change over time. Compare the evolution of medium and high mass stars.