Chapter 12 Outside our solar system.

1. Chapter 12 Outside our solar system. Part 3

2. The Formation of Stars • A star is an object in space made up of hot gases, with a core that is like a thermonuclear reactor.

3. The Formation of Stars • Forms from the materials in a nebula when gravity starts acting on chunks of gas and dust, pulling them together.

4. The Formation of Stars • As gravity keeps working, the mass grows and the material collapses in on itself and contracts. • An early phase of star, called a “protostar,”

5. Life Cycle of a Star • Low mass stars • these stars start small • exist that way for most of their life as dim, cool red dwarfs. • burn their hydrogen fuel very slowly 100 billion years. • Die as hot dim white dwarfs and quietly burn out.

6. Life Cycle of a Star • Intermediate mass stars ( the Sun) • star lasts only about 10 billion years. • long period of stability • expands into a red giant. • slowly shrinking into a small, dim white dwarf. • it cools into a black dwarf, a dense, dark body made up mostly of carbon and oxygen.

7. Life Cycle of a Star • High mass stars • 12 or more times the mass of the Sun • consume their fuel faster than smaller stars • Become red giants. (supergiants) • last for only 7 billion years. • they collapse in on themselves causing a massive explosion called a supernova. • the remaining core of the supernova will eventually collapse to form a neutron star. A sphere only 10 km wide.

8. Life Cycle of a Star High mass stars

9. Common stars and the Sun