Write a sci-fi story about a group of astronauts who land on a distant planet, only to discover that it is populated by highly advanced alien beings who have been observing Earth for centuries

Write a sci-fi story about a group of astronauts who land on a distant planet, only to discover that it is populated by highly advanced alien beings who have been observing Earth for centuries. The aliens have a message for humanity, but it could change the course of human history forever.