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The Future Sun • Homework 5 is due Wed, 24 March at 6:30am • One answer is wrong. See email • OBAFGKM extra credit • Angel: Lessons>Extra Credit • Due 11:55pm, 31 March • Answer on Q36 on Test 2 was wrong. • It will be regraded. • Final exam (new, later time) • 6 May, 3:00-5:00, BPS 1410 • • • Giants are dying stars; white dwarfs are dead stars Why does the sun die? What will the sun become when it dies? Hertzsprung-Russell (H-R) Diagram 1. Stars: A-Aldebaran; B-Barnard’s Star; C-Capella; D-Rigel What do you need to know about stars to answer the next 4 questions?104 Pick one correct ans. a. b. c. d. e. 2. 3. 4. 5. Hot-plate model of star Model of the solar interior How to read H-R Diagram Spectrum of black body Energy generation in the sun Luminosity (Lsun) Î • 1 Which is the hottest star? Which is the smallest star? Which is the biggest star? 10-4 If stars A-D replaced the sun, would people be able to live in Michigan? a. b. c. d. e. YNNN NYNN NNYN NNNY NNNN O B A F G Spectral class 25,000 10,000 6000 Í Temperature (K) K M 3000 [see Fig. 11.10] 1 Hertzsprung-Russell (H-R) Diagram 1. Stars: A-Aldebaran; B-Barnard’s Star; C-Capella; D-Rigel What do you need to know about stars to answer the next 4 questions? Pick one correct ans. a. b. c. d. e. 2. 3. 4. 5. Hot-plate model of star: L=R2T4 Model of the solar interior X How to read H-R Diagram Spectrum of black body: Hotter=>bluer Energy generation in the sun X Which is the hottest star? Which is the smallest star? Which is the biggest star? If stars A-D replaced the sun, would people be able to live in Michigan? a. b. c. d. e. 104 Luminosity (Lsun) Î • 1 10-4 YNNN NYNN NNYN NNNY NNNN O B A F G Spectral class 25,000 10,000 6000 Í Temperature (K) K M 3000 [see Fig. 11.10] Giants are dying stars; white dwarfs are dead stars • Evidence on giants from star clusters • Compare members of a population. (Twin study) M80 • All stars in a cluster are born at once. • Formation time is the collapse time of the cluster, which is very short. • I am a G star like the sun. I have 100,000 fraternal twins, some weighing 30 times my mass, some 1/10 of my mass. Pleiades 2 Star cluster Pleiades HR Diagram of Clusters • Not all fainter stars were observed. • • • For all star clusters, main sequence extends to cooler stars beyond observations In what ways are HR diagrams of H+χ Perseus, Pleiades, Hyades, & NGC188 different? Q Which is false a. Hottest stars in Perseus are hotter than hottest stars in Pleiades. b. Most stars are on the main sequence. c. NGC188 has small range of luminosity d. Some clusters have giants. 3 Stars with high mass live a short life 106 O star: 30M~; 200,000L~ Lifetime=amount of fuel/consumption rate Lifetime=21gallons/(3gallons/hr)=7hr Lifetime=30M~/ 200,000L~ =Lifetime~/7000 =1.3Myr Human scale = 4days, 4,500lb Luminosity → 104 102 0 10Sun Lifetime=10Byr Human scale 80yr, 150lb 10-2 Barnard’s star: 0.1M~; 0.004L~ 10-4 Lifetime=0.1M ~/ 0.004L~ =25Lifetime~ =250Byr Human scale = 20,000yr, 15lb 25,000 10,000 5,000 Temperature 3,000 H-R Diagrams of star clusters • Q2 There are no A stars in M80 because a. they never formed. b. they died and disappeared c. all stars became redder as they get older. d. they are too faint to see. 4 H-R Diagrams of star clusters • Q3 The hottest dwarfs in Pleiades are A stars. The hottest dwarfs in M15 are F stars. Pleiades is ___ than M15. a. older b. younger 5