Europa is there life here Copyright 2009 Pearson Education Inc Pathological Science 1 Discoverers make their claims directly to the popular media rather than to fellow scientists 2 Discoverers claim that a conspiracy has tried to suppress the discovery 3 The claimed effect appears so weak that observers can hardly distinguish it from noise No amount of further work increases the signal 4 Anecdotal evidence is used to back up the claim 5 True believers cite ancient traditions in support of the new claim 6 The discoverer or discoverers work in isolation from the mainstream scientific community 7 The discovery if true would require a change in the understanding of the fundamental laws of nature From Robert Park Copyright 2009 Pearson Education Inc Pathalogical Science 1 The maximum effect that is observed is produced by a causative agent of barely detectable intensity and the magnitude of the effect is substantially independent of the intensity of the cause 2 The effect is of a magnitude that remains close to the limit of detectability or many measurements are necessary because of the very low statistical significance of the results 3 There are claims of great accuracy 4 Fantastic theories contrary to experience are suggested 5 Criticisms are met by ad hoc excuses 6 The ratio of supporters to critics rises and then falls gradually to oblivion From Langmuir Copyright 2009 Pearson Education Inc Copyright 2009 Pearson Education Inc 11 2 Patterns Among Stars Our goals for learning What is a Hertzsprung Russell diagram What is the significance of the main sequence What are giants supergiants and white dwarfs Copyright 2009 Pearson Education Inc What is a Hertzsprung Russell diagram Copyright 2009 Pearson Education Inc Luminosity An H R diagram plots the luminosities and temperatures of stars Temperature Copyright 2009 Pearson Education Inc Generating an H R Diagram Copyright 2009 Pearson Education Inc Most stars fall somewhere on the main sequence of the H R diagram Copyright 2009 Pearson Education Inc large radius Stars with lower T and higher L than mainsequence stars must have larger radii giants and supergiants Copyright 2009 Pearson Education Inc Stars with higher T and lower L than main sequence stars must have smaller radii white dwarfs small radius Copyright 2009 Pearson Education Inc A star s full classification includes spectral type line identities and luminosity class line shapes related to the size of the star I II III IV V supergiant bright giant giant subgiant main sequence Examples Sun G2 V Sirius A1 V Proxima Centauri M5 5 V Betelgeuse M2 I Copyright 2009 Pearson Education Inc H R diagram depicts Temperature Luminosity Color Spectral type Luminosity Radius Temperature Copyright 2009 Pearson Education Inc C B D A Copyright 2009 Pearson Education Inc Which star is the hottest C B D A Copyright 2009 Pearson Education Inc Which star is the hottest A C B D A Copyright 2009 Pearson Education Inc Which star is the most luminous C B Which star is the most luminous C D A Copyright 2009 Pearson Education Inc C B D A Copyright 2009 Pearson Education Inc Which star is a mainsequence star C B Which star is a mainsequence star D D A Copyright 2009 Pearson Education Inc C B D A Copyright 2009 Pearson Education Inc Which star has the largest radius C B Which star has the largest radius C D A Copyright 2009 Pearson Education Inc What is the significance of the main sequence Copyright 2009 Pearson Education Inc Main sequence stars are fusing hydrogen into helium in their cores like the Sun Luminous mainsequence stars are hot blue Less luminous ones are cooler yellow or red Copyright 2009 Pearson Education Inc High mass stars Low mass stars Copyright 2009 Pearson Education Inc Mass measurements of main sequence stars show that the hot blue stars are much more massive than the cool red ones High mass stars Low mass stars Copyright 2009 Pearson Education Inc The mass of a normal hydrogen burning star determines its luminosity and spectral type The core temperature of a higher mass star needs to be higher in order to balance gravity Hydrostatic Equilibrium Copyright 2009 Pearson Education Inc A higher core temperature boosts the fusion rate leading to greater luminosity Stellar Properties Review Luminosity from brightness and distance 10 4LSun 106LSun Temperature from color and spectral type 3 000 K 50 000 K Mass from period p and average separation a of binary star orbit 0 08MSun 100MSun Copyright 2009 Pearson Education Inc Stellar Properties Review Luminosity from brightness and distance 0 08MSun 10 4LSun 106LSun 100MSun Temperature from color and spectral type 0 08MSun 3 000 K 50 000 K 100MSun Mass from period p and average separation a of binary star orbit 0 08MSun 100MSun Copyright 2009 Pearson Education Inc Mass and Lifetime Sun s life expectancy 10 billion years Copyright 2009 Pearson Education Inc Mass and Lifetime Sun s life expectancy 10 billion years Copyright 2009 Pearson Education Inc Until core hydrogen 10 of total is used up Mass and Lifetime Sun s life expectancy 10 billion years Until core hydrogen 10 of total is used up Life expectancy of a 10MSun star 10 times as much fuel uses it 104 times as fast 10 million years 10 billion years 10 104 Copyright 2009 Pearson Education Inc Mass and Lifetime Sun s life expectancy 10 billion years Until core hydrogen 10 of total is used up Life expectancy of a 10MSun star 10 times as much fuel uses it 104 times as fast 10 million years 10 billion years 10 104 Life expectancy of a 0 1MSun star 0 1 times as much fuel uses it 0 01 times as fast 100 billion years 10 billion years 0 1 0 01 Copyright 2009 Pearson Education Inc Main Sequence Star Summary High mass High luminosity Short lived Large radius Blue Copyright 2009 Pearson Education Inc Low mass Low luminosity Long lived Small radius Red What are giants supergiants and white dwarfs Copyright 2009 Pearson Education Inc Off the Main Sequence Stellar properties depend on both mass and age those that have finished fusing H to He in their cores are no longer on the main sequence All stars become larger and redder after exhausting their core hydrogen giants and supergiants Most stars end up small and white after fusion has ceased white dwarfs Copyright 2009 Pearson Education Inc Relationship Between Main Sequence Stellar Masses and Location on H R Diagram Copyright 2009 Pearson Education Inc Giants and supergiants are far larger than main sequence stars and white dwarfs Copyright 2009 Pearson
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