1. Charles Hakes Fort Lewis College1

2. Charles Hakes Fort Lewis College2

3. Charles Hakes Fort Lewis College3 Chapter 10 Measuring the Stars Parallax and Magnitudes

4. Charles Hakes Fort Lewis College4 Misc notes sunspots radiate less energy – overall activity radiates more. magnetic fields disrupt convection remove folder debris

5. Charles Hakes Fort Lewis College5 Chapter 10 Measuring the Stars

6. Charles Hakes Fort Lewis College6 Magnitude Historical Magnitude Scale Hipparcos/Ptolemy The brightest stars were “of the first magnitude” Dimmer stars were second, third, etc. magnitude. Dimmest stars were 6 th magnitude

7. Charles Hakes Fort Lewis College7 Magnitude Modern Apparent Magnitude scale A difference of five magnitudes corresponds to exactly a factor of 100 in brightness. One magnitude is a factor of 100 0.2 = 2.511886 Both negative and positive magnitudes are allowed. Sun -26.8 Sirius -1.4 Faintest stars visible in Durango ~6.5 Magnitudes don’t have to be integers.

8. Charles Hakes Fort Lewis College8 More Precisely 10-1 More on the Magnitude Scale Note relative brightness on the left, and magnitude on the right.

9. Charles Hakes Fort Lewis College9 Review

10. Charles Hakes Fort Lewis College10 Which is the net result of the proton- proton chain? A) 4 protons = 1 helium 4 + 2 neutrinos + energy B) 2 protons = deuterium + a positron + an antineutrino + energy C) 4 protons = 2 helium-2 + 2 positrons + energy D) 6 protons = 2 heliums + 3 positrons + 3 neutrinos + energy E) only energy

11. Charles Hakes Fort Lewis College11 Which is the net result of the proton- proton chain? A) 4 protons = 1 helium 4 + 2 neutrinos + energy B) 2 protons = deuterium + a positron + an antineutrino + energy C) 4 protons = 2 helium-2 + 2 positrons + energy D) 6 protons = 2 heliums + 3 positrons + 3 neutrinos + energy E) only energy

12. Charles Hakes Fort Lewis College12 What evidence do we have for solar convection? A) sunspot polarity B) the Zeeman effect C) neutrino oscillations D) granulation E) nuclear fusion

13. Charles Hakes Fort Lewis College13 What evidence do we have for solar convection? A) sunspot polarity B) the Zeeman effect C) neutrino oscillations D) granulation E) nuclear fusion

14. Charles Hakes Fort Lewis College14 If Vega is apparent magnitude zero, and Deneb first magnitude, then A) Vega is about 100x brighter than Deneb.. B) Deneb is one magnitude brighter than Vega. C) Vega appears 2.5x brighter than Deneb. D) Deneb must be a main sequence star, and Vega a giant. E) Vega must be 2.5x more luminous than Deneb.

15. Charles Hakes Fort Lewis College15 If Vega is apparent magnitude zero, and Deneb first magnitude, then A) Vega is about 100x brighter than Deneb.. B) Deneb is one magnitude brighter than Vega. C) Vega appears 2.5x brighter than Deneb. D) Deneb must be a main sequence star, and Vega a giant. E) Vega must be 2.5x more luminous than Deneb.

16. Charles Hakes Fort Lewis College16 Luminosity Luminosity - How much energy is coming from the star. Solar constant (W/m 2 ) measured above the Earth’s atmosphere.

17. Charles Hakes Fort Lewis College17 Figure 9.3 Solar Luminosity Solar Constant is the energy reaching the Earth above the atmosphere ~1400 W/m 2

18. Charles Hakes Fort Lewis College18 Luminosity Luminosity - How much energy is coming from the star. Solar constant (W/m 2 ) measured above the Earth’s atmosphere. Energy from the sun decreases as 1/r 2 Stars show same decrease with distance.

19. Charles Hakes Fort Lewis College19 Figure 10.4 Inverse-Square Law

20. Charles Hakes Fort Lewis College20 Figure 10.5 Luminosity The more luminous, distant star appears the same brightness as the less luminous, closer star.

21. Charles Hakes Fort Lewis College21 Luminosity Luminosity - How much energy is coming from the star. Solar constant (W/m 2 ) measured above the Earth’s atmosphere. Energy from the sun decreases as 1/r 2 Stars show same decrease with distance. For stars, instead of measuring in W/m 2, use the “magnitude scale.”

22. Charles Hakes Fort Lewis College22 Small Group Exercise (Learning about the 1/r 2 law.) Get in groups of ~four people. Assume each person has a super- deluxe flashlight left turned on by their front door. It is facing the classroom. How much brighter does the closest flashlight look than the farthest flashlight?

23. Charles Hakes Fort Lewis College23 Figure P.12 Parallax Geometry

24. Charles Hakes Fort Lewis College24 Figure P.11 Parallax Recall information from the Prologue

25. Charles Hakes Fort Lewis College25 Figure 10.1 Stellar Parallax

26. Charles Hakes Fort Lewis College26 Distance Analogy If the Sun is a marble… The Earth is a grain of sand 1 m away. The solar system is ~100 m in diameter

27. Charles Hakes Fort Lewis College27 Distance Analogy If the Sun is a marble… The Earth is a grain of sand 1 m away. The solar system is ~100 m in diameter The next star is in Albuquerque!

28. Charles Hakes Fort Lewis College28 Figure 10.2 Sun ’ s Neighborhood

29. Charles Hakes Fort Lewis College29 Parallax Measurements Earth-based measurements can typically be made to 0.03”, or to a distance of ~30 parsecs (pc) Distances to several thousand stars are known this way. The Hipparcos satellite extends the distance to ~200 pc, so distances to nearly one million stars can be measured with parallax.

30. Charles Hakes Fort Lewis College30 Figure 10.3 Real Space Motion - Barnard ’ s Star 22 years apart Nearby stars also show proper motion, or transverse velocities. Only a few hundred show more than 1”/yr

31. Charles Hakes Fort Lewis College31 If a star has a parallax of 0.05”, then its distance must be A) 5 light years. B) 5 parsecs C) 20 light years. D) 20 parsecs. E) 200 parsecs

32. Charles Hakes Fort Lewis College32 If a star has a parallax of 0.05”, then its distance must be A) 5 light years. B) 5 parsecs C) 20 light years. D) 20 parsecs. E) 200 parsecs

33. Charles Hakes Fort Lewis College33 What peak wavelength is emitted in the core of the Sun (T=10 7 K)? A).29 cm B).29 mm C).29 nm D).29  m E).29 km

34. Charles Hakes Fort Lewis College34 What peak wavelength is emitted in the core of the Sun (T=10 7 K)? A).29 cm B).29 mm C).29 nm D).29  m E).29 km

35. Charles Hakes Fort Lewis College35 Compared to the 5800K photosphere, sunspots at 4500K emit what percent energy? A) 26% B) 36% C) 46% D) 56% E) 66%

36. Charles Hakes Fort Lewis College36 Compared to the 5800K photosphere, sunspots at 4500K emit what percent energy? A) 26% B) 36% C) 46% D) 56% E) 66%

37. Charles Hakes Fort Lewis College37 Three Minute Paper Write 1-3 sentences. What was the most important thing you learned today? What questions do you still have about today’s topics?