B1) State the fundamental principle which determines the appearance of a galaxy spectrum. Describe the evolution of the UV/optical/infrared spectrum (300nm to 2000nm) of a galaxy following a large instantaneous burst of star formation at the beginning of the life of the galaxy. Explain the reasons underlying the changes in the different parts of the spectrum from UV to IR. Describe particularly the change from immediately after the starburst to an age 107 years, and then from 107 years to > 10 years. You may assume that there is no further burst of star formation. The largest O-stars may have masses 90 times that of the sun, or even more. Given that Luminosity Mass), and that the lifetime of the sun is 1010 years, what is the lifetime of an O-star? B1) State the fundamental principle which determines the appearance of a galaxy spectrum. Describe the evolution of the UV/optical/infrared spectrum (300nm to 2000nm) of a galaxy following a large instantaneous burst of star formation at the beginning of the life of the galaxy. Explain the reasons underlying the changes in the different parts of the spectrum from UV to IR. Describe particularly the change from immediately after the starburst to an age 107 years, and then from 107 years to > 10 years. You may assume that there is no further burst of star formation. The largest O-stars may have masses 90 times that of the sun, or even more. Given that Luminosity Mass), and that the lifetime of the sun is 1010 years, what is the lifetime of an O-star