Question 13 Choose the answer below which you think is the best answer to Question 13 of the HR Diagram lab. Three students have answered the question, "Why are the stars we perceive as brightest in the night sky really bright?" Their response where: A."I think it's because these stars must be very close to us. That would make them appear brighter to us in the sky." B."I think it's because these stars are very luminous. They are putting out a tremendous amount of energy." C."I think it's because these stars are very close and very luminous." The question that the students answered was why are the brightest stars we see the brightest. Since our perception of brightness is the apparent magnitude and since the HR diagram plots luminosity or absolute magnitude we cannot use the luminosity scale to help us to make our decision. Student C is correct, the perceived brightness of a star depends on the distance and the luminosity. Student B is correct, the perceived brightness of a star depends on the amount of energy that the star emits each second. But if a star is very luminous and very far away, it will be intrinsically bright, but we will perceive it as dim. If a star is very near but not very luminous, it well be intrinsically dim but we will perceive it as bright. Using the overlap feature of the simulator I found that there are a few stars which are both nearby and reasonably luminous. So, I decided to look up what the brightest stars in the sky are. Here is what I found, from brightest to