1. Notes – How Stars Shine Chapter 12, Lesson 2 They Might Be Giants http://www.youtube.com/watch?v=Zbgul1NpEA8

2. How Stars Form In the beginning, the universe consisted of light elements such as hydrogen, helium, and lithium (produced in the Big Bang). Stars form in a nebula, which is a large cloud of gas and dust in space.

3. How Stars Form Interstellar space is the space between stars containing mostly gas and dust at very low densities. In a nebula, density is much greater and clouds form. Gravity forces in a nebula cause matter to form clumps. As particles move closer together, temperature increases.

4. How Stars Form As the clump contracts, it becomes spherical. When it reaches a certain mass, it becomes a protostar, which contracts and increases in temperature.

5. How Stars Form The sphere begins to rotate and flatten into a disk. After millions of years, the temperature is hot enough for fusion to occur. When the central mass reaches 8% that of the Sun, a star is born.

6. How Stars Produce Light Stars emit huge amounts of energy, part of which is visible light. Energy produced during fusion passes through the star and is emitted from its photosphere.

7. How Stars Produce Light In a nuclear fusion reaction, two nuclei combine to form a larger nuclei. In a star’s core, there is a reaction that fuses hydrogen to form helium. Energy is released as gamma rays and neutrinos.

8. How Stars Produce Light Fusion reactions produce outward pressure and causes expansion. Gravity pulls particles toward each other and causes contraction. The length of a star’s life is determined by the balance of these forces.

9. How Stars Produce Light

10. How Stars End Eventually a star converts all its hydrogen to helium. In smaller stars, fusion will continue to convert helium into carbon, nitrogen, and oxygen. In very massive stars, fusion reactions continue to produce heavier elements.

11. How Stars End When fusion stops, there is no longer any force to balance gravity. The result could be a: white dwarf, supernova, neutron star, or black hole.

12. Low-Mass Star Life Cycles Red giants are sun-sized stars that have used up all the fuel in their core and have begun to contract. White dwarfs are red giants that have lost the mass from their surface and only the core remains.

13. Low-Mass Star Life Cycles

14. High-Mass Star Life Cycles A supernova forms when a supergiant explodes before dying.

15. High-Mass Star Life Cycles Neutron stars are the very dense remains of stars after a supernova.

16. High-Mass Star Life Cycles

17. Black holes are created when a neutron star collapses and all its mass is concentrated into a single point.

18. High-Mass Star Life Cycles The gravitation force in a black hole is so great not even light can escape. Black holes can be detected by their influence on other nearby objects.

19. Interstellar space is composed of mainly ____. Anothing Biron Chydrogen Ddust 12.2 How Stars Shine 1.A 2.B 3.C 4.D

20. Which type of star has a density so great that protons fuse to electrons? Ared giant Bsupernova Cneutron star Dwhite dwarf 12.2 How Stars Shine 1.A 2.B 3.C 4.D

21. In nuclear fusion, smaller nuclei fused to form ____. Ahydrogen Bhelium Clighter elements Dlarger nuclei 12.2 How Stars Shine 1.A 2.B 3.C 4.D

22. A supernova could result in the formation of a ____. Asupergiant Bneutron star Cred giant Dwhite dwarf 1.A 2.B 3.C 4.D

23. Our sun will eventually become a ____. Awhite dwarf Bblack hole Cneutron star Ddark planet 1.A 2.B 3.C 4.D

24. The process by which hydrogen is changed to helium in the core of a star is called ____. Anuclear fission Bnuclear reaction Cnucleolus Dnuclear fusion 1.A 2.B 3.C 4.D