1. The Stars Stellar Evolution Created September 2015 by Joshua Toebbe

2. Learning Goals The Stars: Stellar Evolution What happens to a star as it uses up hydrogen? What happens to a star when it exhausts hydrogen? Created September 2015 by Joshua Toebbe

3. H-R Diagrams The Stars: Stellar Evolution As we learned previously stars have a temperature – pressure relationship. The larger the star, the greater the gravitation pressure, the greater the temperature, and the greater the energy production. Therefore the larger stars are brighter. This relationship is shown on a Hertzsprung-Russell diagram. Created September 2015 by Joshua Toebbe

4. H-R Diagrams The Stars: Stellar Evolution As we learned previously stars have a temperature – pressure relationship. The larger the star, the greater the gravitation presser, the greater the temperature, and the greater the energy production. Therefore the larger stars are brighter. This relationship is shown on a Hertzsprung-Russell diagram. Created September 2015 by Joshua Toebbe cold Warm

5. Stellar Evolution The Stars: Stellar Evolution For most of a stars lifetime it will fuse hydrogen into helium. But as it does it runs out of hydrogen fuel and helium begins to pile up in the core. This dramatically changes the life of a star as well as its position on an H-R diagram. The process a star goes through as it burns and then uses up its hydrogen fuel is known as stellar evolution. Created September 2015 by Joshua Toebbe

6. Stellar Evolution The Stars: Stellar Evolution Created September 2015 by Joshua Toebbe

7. Stellar Evolution The Stars: Stellar Evolution Video summary of stellar evolution As a star fuses hydrogen helium accumulates until fusion stops Core contracts igniting hydrogen shell fusion around the core Outer layers expand and star cools while growing brighter Core continues to collapse igniting helium fusion in core Star begins to shrink and grow hotter As a star fuses helium carbon accumulates until fusion stops Core contracts igniting helium shell fusion Outer layers expand and cool again Core continues to collapse and star fuses heavier elements Created September 2015 by Joshua Toebbe

8. Sources Cover image underlay: from genkkis.deviantart.comgenkkis.deviantart.com HR-Diagram image: from cococubed.asu.educococubed.asu.edu Seeds, M. A. [2008] Foundations of Astronomy: Tenth Edition. Thomson, Brooks/cole. Created September 2015 by Joshua Toebbe The Stars: Stellar Evolution