142 Galaxy Classification 12) Consider the discussion among three students about

Question

142 Galaxy Classification 12) Consider the discussion among three students about a galaxy that appears red. Because there is mainly red light in this galaxy and no blue light, I think that only small, red stars formed in this galaxy and not any big, blue ones. Idisagree. It's just that blue stars don't last very long. I think the blue stars that may have been there in the past have already evolved into red giants, so the galaxy looks red due to the light from all the red giants Wait a minute. I think you are both wrong. I thought that both blue stars and red giants live short lives, so they should both be gone. I think that all the blue stars that formed early on have evolved into the red stars that are there now. So the galaxy appears red because it's full of a lot of old, red stars that used to be the blue stars. Student 1: Student 2: Student 3: Do you agree or disagree with any or all of the students? Explain your reasoning. 13) Hubble imagined the tuning Normal Spirals Sb fork diagram (shown at right) as representing an evolutionary sequence for galaxies, with galaxies starting off as elliptical and developing more structure over time. Do you think Hubbles proposed evolutionary sequence is correct? Why or why not? Sa Sc Ellipticals Irregulars SBO Lenticular Galaxy SBa SBb Barred Spira SBc

Explanation / Answer

Answer - Students 3 is correct hence agree with because of - Blue: a region with many young stars. High-mass stars live fast and die young, using fuel at a high rate to maintain high temperatures. This causes them to emit hot radiation, which is blueish. And Red: a region of old stars. The high-mass stars have swollen and cooled, and the low-mass stars were never hot to begin with, so they both emit cool radiation, which is reddish.

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