1. Stars

2. Constellations A group of stars that appears to form a pattern in the sky A group of stars that appears to form a pattern in the sky Virgo AQUARIUS

3. Constellations - total of 88 different constellations can be seen in the N and S hemispheres As you move north you can see more stars. Andromeda Aries

4. Constellations- Ursa Major - (Big Bear) is the most famous constellation

5. Constellations- The Big Dipper is part of Ursa Major

6. Constellations- Two stars of Ursa Major are used to find the North star- Polaris- (pole star) Polaris ?1&2

7. Constellations- Polaris is part of Ursa Minor (the little dipper) Polaris is part of Ursa Minor (the little dipper) Ursa Minor

8. Constellations- As the earth rotates on its axis the constellations move. As the earth rotates on its axis the constellations move. They rotate around Polaris counter clockwise. They rotate around Polaris counter clockwise. The earth’s axis points toward the N. Star The earth’s axis points toward the N. Star Pg. 617 (fig. 28.2)

9. Constellations- Some constellations can only be seen during specific seasons Some constellations can only be seen during specific seasons This is due to earth’s rotation around sun and tilt of the earth This is due to earth’s rotation around sun and tilt of the earth Lyra in summer Orion in Winter ?3,4&5

10. Circumpolar Rotation around Polaris

11. What happens as you travel North? The number of circumpolar stars visible, increases as the observer moves North The number of circumpolar stars visible, increases as the observer moves North

12. Can you tell what constellations these are?

13. Ursa Major ?6

14. Lyra ?7

15. Orion ?8

16. Aquarius

17. Gemini

18. Stars- How far to a star? Closest Star = Sun Closest Star = Sun 93,000,000 miles = 1 astronomical unit 93,000,000 miles = 1 astronomical unit Next closest star Next closest star  Proxima Centauri  25 trillion miles  2.5 x 10 13  4.2 light years

19. Light year- Distance that light travels in one year Distance that light travels in one year 5,900,000,000,000 miles 5,900,000,000,000 miles Polaris- 680 LY Polaris- 680 LY Betelgeuse (red supergiant ) is 490 LY Betelgeuse (red supergiant ) is 490 LY ?9

20. Properties of Stars Our Sun- Our Sun-  Diameter-  855600 miles  110x earth  Density  1.4 x density H 2 0  Mass  300,000x earth

21. How does our sun compare? Diameter- Diameter-  average Density- Density-  mid to high Mass- Mass-  Other stars range from 1/100 th to 50x our sun

22. How do we size up?

23. Wow! Jupiter is BIG

24. Our sun is REALLY BIG!

25. Guess Not!

26. We are REALLY SMALL! I feel so insignificant!

27. Color?Color? Depends on surface temperature cool Medium- our sun (5500°C) Hot- ~30,000 ° C

28. Classification of stars Green stars look white to us!

29. Composition of Stars- How can we tell? How can we tell? Our sun- Our sun-  Hydrogen (70%)  Helium (28%) No 2 stars have the same spectra (like a fingerprint) No 2 stars have the same spectra (like a fingerprint) You know this! Spectroscopy! ?10 & 11

30. -Brightness- Apparent Magnitude- Apparent Magnitude-  how bright a star appears to earth observer.  Depends on  Distance from us  what is between us  true brightness

31. Brightness- Luminosity-  True brightness  Depends on…(2 things) 1.Size -if same size, blue is more luminous 2.Temp.- if same temp., bigger is more luminous

32. Absolute Magnitude- How stars would appear if they were all the same distance from earth. All stars place 32.6 LY from the sun Our sun abs. Mag = 4.8 Negative is brighter Rigel- foot of Orion 40,000 suns “Blue Super Giant” ?12