This is the “observable universe.” Everything you can see has to be inside a sphere centered at your head whose radius is the distance that light can have traveled since the universe was born. If a point on the surface of that sphere sent you a photon at the earliest possible moment, it will only be arriving now; that is what defines the edge of our vision. Light from stars, planets, and kittens outside that sphere will not yet have reached us, so no telescope can see them. Even a superbright supernova or a giant planet-size pink kitten would be invisible to us if it was outside that sphere.
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