Looking up into the night sky, it’s challenging enough for an amateur astronomer to count the number of naked-eye stars that are visible. With bigger telescopes, more stars become visible, making counting impossible because of the amount of time it would take. So how do astronomers figure out how many stars are in the universe?
By Elizabeth Howell—Space.com
The first sticky part is trying to define what “universe” means, said David Kornreich, an assistant professor at Ithaca College in New York State. He was the founder of the “Ask An Astronomer” service at Cornell University.
“I don’t know [the answer] because I don’t know if the universe is infinitely large or not,” he said. The observable universe appears to go back in time by about 13.7 billion light-years, but beyond what we could see there could be much, much more. Some astronomers also believe that we may live in a “multiverse” where there would be other universes like ours contained in some sort of larger entity.