Charles Hakes Fort Lewis College1

Charles Hakes Fort Lewis College2

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

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

Charles Hakes Fort Lewis College5 Misc notes Problem 9.1 Should say “Section 9.1” and NOT And note that Mercury’s orbit is very eccentric, so you can’t simply use the semi-major axis for it’s distance at perihelion.

Charles Hakes Fort Lewis College6 Star Party Discovery Museum - tonight 6:30

Charles Hakes Fort Lewis College7 Review

Charles Hakes Fort Lewis College8 Which is the net result of the proton- proton chain? A) 4 protons = 1 helium neutrinos + energy B) 2 protons = deuterium + a positron + an antineutrino + energy C) 4 protons = 2 helium positrons + energy D) 6 protons = 2 heliums + 3 positrons + 3 neutrinos + energy E) only energy

Charles Hakes Fort Lewis College9 Which is the net result of the proton- proton chain? A) 4 protons = 1 helium neutrinos + energy B) 2 protons = deuterium + a positron + an antineutrino + energy C) 4 protons = 2 helium positrons + energy D) 6 protons = 2 heliums + 3 positrons + 3 neutrinos + energy E) only energy

Charles Hakes Fort Lewis College10 What evidence do we have for solar convection? A) sunspot polarity B) the Zeeman effect C) neutrino oscillations D) granulation E) nuclear fusion

Charles Hakes Fort Lewis College11 What evidence do we have for solar convection? A) sunspot polarity B) the Zeeman effect C) neutrino oscillations D) granulation E) nuclear fusion

Charles Hakes Fort Lewis College12 Compared to the Earth, the Sun’s average density is: A) lower B) about the same C) much greater

Charles Hakes Fort Lewis College13 Compared to the Earth, the Sun’s average density is: A) lower B) about the same C) much greater

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.

Charles Hakes Fort Lewis College15 Chapter 10 Measuring the Stars

Charles Hakes Fort Lewis College16 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

Charles Hakes Fort Lewis College17 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 = Both negative and positive magnitudes are allowed. Sun Sirius -1.4 Faintest stars visible in Durango ~6.5 Magnitudes don’t have to be integers.

Charles Hakes Fort Lewis College18 More Precisely 10-1 More on the Magnitude Scale Note relative brightness on the left, and magnitude on the right.

Charles Hakes Fort Lewis College19 Luminosity Luminosity - How much energy is coming from the star. Solar constant (W/m 2 ) measured above the Earth’s atmosphere.

Charles Hakes Fort Lewis College20 Figure 9.3 Solar Luminosity Solar Constant is the energy reaching the Earth above the atmosphere ~1400 W/m 2

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.

Charles Hakes Fort Lewis College22 Figure 10.4 Inverse-Square Law

Charles Hakes Fort Lewis College23 Figure 10.5 Luminosity The more luminous, distant star appears the same brightness as the less luminous, closer star.

Charles Hakes Fort Lewis College24 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.”

Charles Hakes Fort Lewis College25 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?

Charles Hakes Fort Lewis College26 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.

Charles Hakes Fort Lewis College27 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.

Charles Hakes Fort Lewis College28 Figure P.12 Parallax Geometry

Charles Hakes Fort Lewis College29 Figure P.11 Parallax Recall information from the Prologue

Charles Hakes Fort Lewis College30 Figure 10.1 Stellar Parallax

Charles Hakes Fort Lewis College31 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

Charles Hakes Fort Lewis College32 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!

Charles Hakes Fort Lewis College33 Figure 10.2 Sun ’ s Neighborhood

Charles Hakes Fort Lewis College34 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.

Charles Hakes Fort Lewis College35 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

Charles Hakes Fort Lewis College36 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

Charles Hakes Fort Lewis College37 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

Charles Hakes Fort Lewis College38 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

Charles Hakes Fort Lewis College39 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

Charles Hakes Fort Lewis College40 Compared to the 5800K photosphere, sunspots at 4500K emit what percent energy? A) 26% B) 36% C) 46% D) 56% E) 66%

Charles Hakes Fort Lewis College41 Compared to the 5800K photosphere, sunspots at 4500K emit what percent energy? A) 26% B) 36% C) 46% D) 56% E) 66%

Charles Hakes Fort Lewis College42 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?