b.) You take a spectrum of a galaxy and determine that the absorption lines in the spectrum are shifted toward the red end of the spectrum. What does that tell you about the Galaxy?
c.) Two stars are the same size. One star has a temperature of 6,000K and the other 12,000K. How much more energy per second is the hotter star emitting compared to the cooler star?What are the two quantities you need to know to determine the energy per second being emitted by a star?You need to know it's physical size and surface area as well as the surface temperature to determine how much energy a star is radiating. A galaxy that has a red shifted spectrum is speeding away from the Earth, and the greater the velocity, the greater the red shift. The greater the red shift, the greater the distance from Earth. This was how Edwin Hubble discovered that the Universe is in fact expanding. As for a star surface temperature, if the temperature is doubled, each unity of surface area emits two to the fourth power more light than before. That means when two stars of the same physical size, but one with twice the surface temperature of the other, the hotter star will emit 16 times as much energy, all other factors being equal.What are the two quantities you need to know to determine the energy per second being emitted by a star?Well, I know for a fact that a red shift means that galaxy is moving away from the point of observation.
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