The Borderland of Sol is an English language science fiction novelette written in 1975 by Larry Niven. It is the fifth in the Known Space series of stories about crashlander Beowulf Shaeffer.
It includes some solid science as well as 'space opera'. It is one of the earliest works of fiction to feature a black hole.
Segments of the novel Fleet of Worlds serve as a prequel to the story.
A rash of spaceship disappearances around Earth results in a dearth of available transit, stranding Beowulf "Bey" Shaeffer on Jinx away from his love, Sharrol Janss. While visiting the Institute of Knowledge he runs into his old friend Carlos Wu. Carlos is the father of Janss' two children, a fact that he found so embarrassing that he decided to leave Earth rather than face Bey upon his expected return. But Bey proves perfectly happy to hear about the children, as his albinism denies him a license to have children of his own, and he and Sharrol had agreed that Carlos should act as a surrogate.
Reconciled, Carlos mentions that he has been contacted by Sigmund Ausfaller of the Bureau of Alien Affairs, who has offered him a ride to Earth. Bey has had several run-ins with Ausfaller in the past; Ausfaller aims to protect human-alien relations in any way he can, and at one point he planted a bomb on Bey's alien-provided General Products' #2 hull to prevent him from stealing it and potentially causing a sticky diplomatic incident. Worried about what might happen to Carlos at Ausfaller's hands, he decides to accompany him on his next meeting...
The story is retold, from the point of view of Sigmund Ausfaller, in Juggler of Worlds.
Beowulf Shaeffer stories
Neutron Star, the first story in the Beowulf Shaeffer series.
At the Core, the second story in the series.
Flatlander, the third story in the series.
Grendel, the fourth story in the series.
Borderland of Sol, fifth story about Beowulf Shaeffer
Procrustes, the sixth story in the series.
Ghost, the framing story in the collection Crashlander.
Fly-By-Night, the seventh story in the series, written after Crashlander.