HOMEWORK SET 6 SOLUTIONS 1- a- (MAX = 2.9 x 10-3 m K T (10000k = 2898 x 10-10 m ultraviolet (6000k = 4800x 10-10 m visible ( blue ) (2000k = 14500 x 10-10 m infrared b- light from the sun is highly visible and in the photosphere of the sun where light is emitted the temperature is about 6000 k ( so this is the best curve ) to see roughly what the graph looks like , please ask your TA. 2- it takes place in the core of stars because is the only place with the right pressure and temperature ( both need to be extremely high ). In the sun you have hydrogen converted into helium (via the proton-proton of p-p cycle). Fusion in the sun happens at 15 million degrees Kelvin (15,000,000 K ). The core is 2500 times hotter than the surface. 3- to see how to use the graph please ask you TA. a- the horizontal axis tells us how hot or cold the stars are so the closer we are to the origin , the hotter it gets ( beginning of the axis ). Therefore #2 is the hottest ( G0) and #4 is the coldest(#4). b- Luminosity M can change from eye to eye, we need to use the graph since M is the vertical axis, the higher up the more luminous so # 3 is the more luminous and #5 the least luminous. M1= 2, M2=-1, M3= -7, M4=0, M5=7 c- Since distance d is proportional to m-M ( no units necessary, just relative distance to each other) the star with the biggest difference is the farthest ( # 2 ) and closest with the smaller difference ( # 1 & # 5 ). m-M1= -2 m-M2= 21 m-M3= 10 m-M4= 12 m-M5= -2 4- very similar to the problem of last week R Sirius = 1.8 R sun L sirius is proportional to R2 T4 ( of the sirius ) L sun is proportional to R2 T4 ( of the sun) Take ratios L Sirius / L sun = 1.8 2 x 10000 4 1 x 6000 4 L Sirius/ L sun = 25 5- a- source is gravitational potential energy ( gravity ) which later on is transformed into heat and light since energy is conserved. b- when at its center it has the temperature and pressure enough to produce nuclear fusion. c- when it runs out ouf its hydrogen fuel and all of its hydrogen has been converted into helium.