Prepare your scantron: Use a pencil, not a pen! Fill in your name and fill the bubbles under your name. LAST NAME FIRST, First name second Put your 4-digit code instead of “IDENTIFICATION NUMBER”. --- (The last 4 digits of your OleMiss ID.) Question # 1: answer A Question # 2: answer C Question # 3: answer E Setup: Pass-fail makeup: April 2 (Tuesday) 6:00 pm Recall reading assignment: Chapter 17 (“Star stuff”): pp. 532 – 554 Please take a moment to mute your cell phone!

Review questions coming …

This question counts double! sec 10 9 11 13 14 8 12 6 2 1 3 4 15 5 7 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22 Question 4 What spectral type is the Sun? A Type O. B Type A. C Type G. D Type K. E Type M. Next question coming …

This question counts double! sec 10 9 11 13 14 8 12 6 2 1 3 4 15 5 7 16 26 25 27 28 30 29 17 24 19 18 23 20 22 21 Question 5 What is the meaning of Wien’s law in words? That thermal glow’s strongest wavelength is inversely proportional to the temperature. A That. B That. C That. D That. E That.

This question counts double! sec 10 9 11 13 14 8 12 6 2 1 3 4 15 5 7 16 26 25 27 28 30 29 17 24 19 18 23 20 22 21 Question 6 What is the meaning of Stefan-Boltzman’s law in words? That the intensity of thermal glow per square inch is proportional to the 4th power of the temperature. A That. B That. C That. D That. E That.

This question counts double! sec 10 9 11 13 14 8 12 6 2 1 3 4 15 5 7 16 26 25 27 28 30 29 17 24 19 18 23 20 22 21 Question 7 What two things are related by the Hertzsprung-Russel diagram (the HRD)? A The absolute brightness and the temperature of stars. B The size and the absolute brightness of stars. C The apparent brightness and the spectral type of the star. D The size and the apparent brightness of a star.

An example: how far is Spica? Brightness: 1mg (fairly bright) Color: B (bluish-white) Find M from HRD: M=-6mg (very bright) Looks 7mg fainter than it really is: distance modulus = 7 mg distance is 90 pc = 270 light years Parallax method would not work well - too far Example: Spica

An application: star clusters Recall what they are: a bunch of stars together • close to each other (less than a light year) • all part or our Galaxy Use for clusters The Pleiades (M45) A globular cluster (M10) The Beehive (M44) Two open clusters

Clusters are useful for studying stars: same distance, same age Prepare HRD of all stars of a cluster: Cluster HRD Find: • Many stars on the main sequence • Above a “turnoff”, stars are to the right of the main sequence Meaning: something happened to these (these stars are the brightest in the cluster) Jump ahead: they have used up all their hydrogen Place of turnoff indicates age: • Pleiades is young • w Cen is old Pleiades w Centauri

Questions coming …

sec 10 9 11 12 15 14 13 8 7 1 2 3 5 4 6 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22 Question 8 What is a star cluster is made of? A Galaxies. B It is a cloud of gas. C Many stars. Next question coming …

sec 10 9 11 12 15 14 13 8 7 1 2 3 5 4 6 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22 Question 9 What can you read off the Hertzsprung-Russel diagram (HRD) of a star cluster? A How bright it is. B How old it is. C How large it is. D How far it is. E How dense it is. Next question coming …

sec 10 9 11 13 14 8 12 7 2 1 3 4 6 5 15 17 26 25 27 28 30 29 16 24 19 18 23 20 22 21 Question 10 Which one contains more stars, an open cluster or a globular cluster? A An open cluster. B A globular cluster. C The same. D Neither, because both are gas clouds.

What is where in the HRD?

The significance of stellar mass Mass tells: • rate of evolution • location on main sequence • whether star blows up as supernova Stellar masses The heaviest star: 80 M Short life very bright blue, hot dies as a (10 million yrs) (-10 mg) (O5) supernova The lightest star: 0.1 M Long life very faint red, lukewarm dies as a (100 billion yrs) (+15 mg) (M5) white dwarf

Questions coming …

sec 10 9 11 12 15 14 13 8 7 1 2 3 5 4 6 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22 Question 11 What determines the length of life of a star? A All stars live the same length of time. B The temperature in its center. C Its chemical composition. D Its mass. E Its magnetic field. Next question coming …

sec 10 9 11 12 15 14 13 8 7 1 2 3 5 4 6 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22 Question 12 A hot, blue star on the main sequence is … A heavy B faint C far away D burning helium E has no fuel left to burn Next question coming …