Evolution of Stars Lesson 3 page 816

Life Cycle of a Star pg. 817 1. What is a nebula? A cloud of dust and gas where stars are formed.

2. Describe in detail how a star is born: Gravity causes the densest parts of nebulae to collapse into protostars. Protostars pull in more and more gas until their cores are hot and dense enough for fusion to start.

3. When do stars become main sequence stars 3. When do stars become main sequence stars? As soon as it begins to fuse hydrogen into helium. Describe the lifecycle of a massive star. (Use diagrams and labels)

3a. What will happen to our star (the Sun) in about 5 billion years 3a. What will happen to our star (the Sun) in about 5 billion years? (Use diagrams and labels)

End of a Star page 819 4. What is a white dwarf? A hot, dense, slowly cooling sphere of carbon. A single sugar cube sized amount of white dwarf would weigh about 1 ton A white dwarf was once the size of the sun, but has been squeezed down to the size of the Earth. A white dwarf has burned off all its fuel and only carbon remains.

5. Supernova- Stars with 10X the mass of the sun do not become white dwarfs. Instead, they explode. A supernova is an enormous explosion that destroys a star.

6. Neutron Star: A dense core of neutrons that remains after a supernova. The core is about 20 km wide. A spoonful would weigh more than 1 billion tons.

7. What is a black hole? An object whose gravity is so great that no light can escape it.

Recycling Matter page 821 8. What happens to the material after a star dies? It is recycled and becomes the building blocks of new stars and planets.

We are made of stars! Once helium runs out, the nuclei of carbon, oxygen, and other elements begin to fuse together. Since the heaviest element created in a star by nuclear fusion reaction is iron, a large iron core eventually forms at the center. At this point, gravity becomes overwhelming, the core collapses, and an explosion occurs (supernova), during which outer layers of gas and heavy elements are ejected to space. These elements are recycled, form planets, and eventually the things on the planets like life!

9. Planetary Nebulae- The remaining hydrogen and helium that surrounds a white dwarf.

10. Supernova remnants: The expanding cloud of dust and gas after a star explodes.

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