The number of stars in the observable universe is really big, but perhaps not as big as you are thinking. Wolfram Alpha gives it as 10^24, which seems like a

The number of stars in the observable universe is really big, but perhaps not as big as you are thinking. Wolfram Alpha gives it as 10^24, which seems like a ludicrously huge number. But suppose for the sake of argument that intelligent human life on Earth were the consequence of just five independent "one in a million" chances. That's 1 in 10^30. Just five independent "one in a million" hurdles to clear makes intelligent life unlikely to occur anywhere in the universe at all. Now consider that advanced human life took a very long time to develop on Earth, even after multicellular life took off, which itself took a very long time to happen. Assuming that evolution inevitably converges onto something like humans is anthropocentric. It may be the case that life is reasonably common but intelligent life such as us is an absurdly rare fluke of luck.