Somnium, written in 1608 by Johannes Kepler, is one of the first space exploration stories. It includes actual astronomy information in a narrative manner.
Vivid story taking place on an ocean planet whose inhabitants occupy cities built on islands of seaweed. These inhabitants are capable of interstellar travel as well as diplomacy with other intergalactic species.
"The Emissary" is a novelette written by Jim Brown and first published in the July 1952 edition of Astounding Science Fiction. The story focusses on an alien taken captive by humans after humans invade the alien's home planet, Sirius A.