If you put all of the stars in the night sky together, how bright would Earth’s sky be?

Each star emits the same amount of light, regardless of location. Image credit: ESO/A. Santerne

Asked by Mike Reynolds

The sky would be about as bright as it is now. Regardless of where the stars are positioned in our night sky, they would still output the same amount of light. This total output across the entire night sky would remain constant if the stars weren’t themselves changed. This is, of course, assuming we simply move the stars so they all appear to be next to each other in the night sky. If we moved them so they occupied the same space, they would collapse under the collected mass and become a black hole. We could observe a change in brightness if we changed the distance between the Earth and the stars we see – as they got closer brightness would increase, and as they moved away brightness would decrease. However, altering the universe on that sort of scale may have more issues than just a brighter night sky for us.

Tags: All About Space, astronomy, Black Hole, brightness, light, night sky, Q&A, space, stars