1. TODAY’S VOCABULARY STAR MAGNITUDE: A term used to describe the brightness of a star.

2. NOTE: THE BIGGER THE NUMBER, THE DIMMER THE STAR

3. ASTRONOMY UNIT INVESTIGATING THE HR DIAGRAM

4. STAR CHARACTERISTICS

5. STAR COLOR Shows the SURFACE TEMPERATURE of the star RED = COOLER BLUE = HOTTER

6. Each temperature range was given its own SPECTRAL CLASS

9. Other Characteristics STAR BRIGHTNESS Depends on three things: Size of the star Temperature of the star How far away STAR BRIGHTNESS Depends on three things: Size of the star Temperature of the star How far away

10. Star Luminosity Defined as how much energy a star is giving off

11. The Hertzsprung-Russell Diagram 1910 Two scientists: Ejnar Hertzsprung and Henry Norris Russel 1910 Two scientists: Ejnar Hertzsprung and Henry Norris Russel

12. AXES LUMINOSITY (brightness) VS SURFACE TEMPERATURES Discovered a pattern….

14. Main Sequence Stars Stars that are fusing H + H = He +energy Stars that are fusing H + H = He +energy SIRIUS A OUR SUN

15. White Dwarfs Stars that are very hot (25,000K) and very small (size of the earth) Ring-Like Planetary Nebula SuWt 2

16. Giants and Supergiants Huge stars (100 – 1000 times the size of our sun) Relatively cool ( 3,000K = red cool) Some are called RED GIANTS Extremely hot (30,000K = blue color) Huge stars (100 – 1000 times the size of our sun) Relatively cool ( 3,000K = red cool) Some are called RED GIANTS Extremely hot (30,000K = blue color)

18. UY Scuti

19. Betelguese

20. ANTERES A

22. What does this pattern mean? The stars in the universe are at different stages in their life cycles. Some stars are young and hot Others are older and colder. https://www.youtube.com/watch? v=ZXpuDXOHeLo

23. Video clip…. https://www.youtube.com/watch?v=UIoA1 P30HrM https://www.youtube.com/watch?v=UIoA1 P30HrM https://www.youtube.com/watch?v=jiSN95 WX1NA https://www.youtube.com/watch?v=jiSN95 WX1NA https://www.youtube.com/watch?v=UIoA1 P30HrM https://www.youtube.com/watch?v=UIoA1 P30HrM https://www.youtube.com/watch?v=jiSN95 WX1NA https://www.youtube.com/watch?v=jiSN95 WX1NA

24. Review so far…. https://www.youtube.com/watch?v=7t3aXb 3LpWg https://www.youtube.com/watch?v=7t3aXb 3LpWg https://www.youtube.com/watch?v=U1Zrar yH3eI https://www.youtube.com/watch?v=U1Zrar yH3eI https://www.youtube.com/watch?v=7t3aXb 3LpWg https://www.youtube.com/watch?v=7t3aXb 3LpWg https://www.youtube.com/watch?v=U1Zrar yH3eI https://www.youtube.com/watch?v=U1Zrar yH3eI

25. TODAY’S ACTIVITY HR DIAGRAM WS Due end of the hour HR DIAGRAM WS Due end of the hour

26. TICKET OUT THE DOOR In general, hotter temperature star will look brighter than lower temperature stars. Our sun is average temperature – about 6000K. This is much, much cooler than the blue supergiants – about 30,000K So….. Why does the sun look so bright? In general, hotter temperature star will look brighter than lower temperature stars. Our sun is average temperature – about 6000K. This is much, much cooler than the blue supergiants – about 30,000K So….. Why does the sun look so bright?