1. Life Cycle of a star HR Diagram Review

2. The HR (Hertzsprung-Russel) Diagram

3. What patterns can be seen? 1.Main Sequence: Most stars fall in this diagonal area 2.Giants: Have bright stars at the right 3.Supergiants: Have the brightest stars in the top center 4.White Dwarfs: Hot stars, but not very bright at the bottom left or bottom center

4. Birth of a Star Stars begin their lives as parts of NEBULAS (gas clouds) which are large clouds of gas and dust spread out. Gravity then acts on the nebulas pulling them closer, increasing the pressure until they start burning. This is called a PROSTAR.

5. Death of a Star Most stars burn H 2 gas and are on the Main Sequence. When a star runs out of fuel (H 2 ), it starts to “die”. Depending on its mass, it may either become a giant or a supergiant which burn Helium gas.

6. Low or Medium mass stars (1.5 -3 times the Sun’s mass) Low or medium mass stars become red giants. Dying stars expand and form planetary nebulae. The remaining blue-white core is called a “White dwarf” When the star is dead it stops glowing and becomes a black dwarf. http://phschool.com/atschool/phsciexp/active_ art/stellar_evolution/index.html

7. High mass stars (More than 3 times the Sun’s mass) When the fuel of high mass stars run out, they quickly evolve into brilliant supergiants. Supergiants can collapse on themselves and explode as a SUPERNOVA. After the Supernova, gravity packs the remaining mass into a smaller space. The gravity is so strong that even light cannot escape. This is called the Black Hole. http://phschool.com/atschool/phsciexp/active_art/st ellar_evolution/index.html http://www.space.com/10411-supernova- destroyer-creator.html

8. Now http://sunshine.chpc.utah.edu/labs/star_ life/hr_interactive.html Draw the diagram to show the life cycle of a star

9. The HR (Hertzsprung-Russel) Diagram

10. H-R diagram questions 1.Where are most stars located on the HR diagram? 2.What color are the hottest stars on the HR diagram? 3.Where are the hottest stars located on the HR diagram? 4.Name a few hot stars. 5.What color are the coolest stars on the HR diagram? 6.Where are the coolest stars located on the HR diagram? 7.Name a few cool stars. 8.What are the 4 types of stars? 9.Where are the brightest stars located? 10.Name some of the brightest stars?