1. H-R diagram

2. Stellar life recap Stars begin as a If they reach ___________________ They move onto the ________ __________ They spend most of their lives here burning _________ Nebula Critical Temperature MainSequence Hydrogen

3. Dying stars Stars start to die when they run out of hydrogen As they age into ___________giants, they cool down but get larger. They then begin to burn The __________stars burn much hotter and brighter, but are then much ___________ as they have collapsed into a white dwarf or supernova. These oldest stars are _________ or ____________. Red Helium Older Smaller BlueWhite

4. Stars the Size of the Sun Die as Stars larger than the sun die as White Dwarves Supernova, neutron stars or black holes

5. Reading the H-R The H-R diagram classifies stars by Surface Temperature Color Luminosity Spectral Class

6. Definitions Luminosity – how truly bright it is based on the sun Ex: it is 100,000 brighter than the sun – It is as bright at 7598 suns Stars can be hundreds of times brighter or dimmer than our sun They are so far away that they appear dim This is also called Absolute Magnitude

7. Spectral Classes Temperature (may vary on HR) O > 20,000K Blue Stars B 10,000 - 20,000 K Blue - white A 7,500 - 10,000 K White stars F 6,000 - 7,500 K Yellow-white stars G 5,000 - 6,000 K Yellow stars (like the Sun) K 3,500 - 5,000K Yellow-orange stars M < 3,500 K Red stars O h, B e a F ine G irl/ G uy, K iss M e

8. Spectral classes O,B, A, F, G, K, M Means absolutely nothing.

9. Other things we can determine Age Is it burning hydrogen, helium or carbon Size compared to the sun

10. Read the H-R diagram Which stars are the hottest? – Blue and white stars Which are the coolest? – Red and Orange Giants Which are the oldest – White dwarfs. – Which star is older: Sirius or Betelguese – Which star is more luminous: Sirius or Betelguese?

11. Star Life Cycles – Recap Stars begin as Protostars Main SequenceCritical Temperature Helium Hydrogen Oldest Red Smaller Blue White If they reach, they move onto the Where they spend most of their lives burning As they age into giants, they cool down but get larger. At this point they are burning The stars burn much hotter and brighter but are then much as they have collapsed into white dwarfs or supernova. These oldest stars are or in color.

12. SuperNOVA in M82

13. What is the H-R Diagram http://aspire.cosmic- ray.org/Labs/StarLife/hr_diagram.html http://aspire.cosmic- ray.org/Labs/StarLife/hr_diagram.html Follow the above link to learn about the HR Diagram Complete the activity online and show your teacher your work.