Well, we haven't really been to the outer limits of the universe. We haven't even been to the outer limits of our own galaxy. Our sun and the planets are just one dot among that spiral of lights and that spiral of lights is just one dot among billions of galaxies in the universe. And, I'm pretty sure there is still stuff about our own ocean that we don't know. But, even if we did explore all that stuff, we probably still wouldn't find a heaven or a hell, at least not as they're described in most religious mythologies. It isn't so much that there isn't space for them, or that similar things don't exist (I'm sure there are paradise planets and hellish planets) it's just that none have any sort of connection to a deity. Unless your definition of god is less about a supreme being and more about energy and the universe.