The Jupiter Theft

The Jupiter Theft is a 1977 novel by science fiction writer Donald Moffitt, re-printed in 2003 with a new afterword. The initial part of the novel mixes near-future thriller and disaster novel scenarios, focussing on the discovery of a moving gamma-ray source headed towards Earth from the direction of Cygnus X-1, and the diversion of a Chinese-American Jupiter mission to investigate the new Solar System intruder. As the Chinese and Americans are mutually antagonistic politically, espionage and suspicion must be overcome for the Jupiter Mission to go ahead.

Once the Mission intercepts the intruder the story shifts into an alien contact scenario. The "intruder" is actually the silicate core of a Jovian planet, orbited by a moon and five immense alien spacecraft. The Jupiter Mission is intercepted in mid-space by aliens, dubbed Cygnans, riding on matter-annihilation powered "broomsticks". The mission is essentially destroyed, with the surviving crew taken alive as specimens for a Cygnan zoo. Now imprisoned, the Sino-American crew attempt contact with the Cygnans and seek to discover their true purpose in appearing in the Solar System. Using a Moog synthesizer, via an early example of sampling in fiction, one of the crew who possesses perfect pitch learns the Cygnan musical language, and is educated by Cygnan didactic films. What he discovers is the Cygnans have travelled for six million years from the progenitor star of Cygnus X-1, now a black hole, and to do so have raided numerous star systems for Jupiter-mass planets to use as fuel.

With help from fluffy pink bird-like humanoids from 61 Cygni, fellow zoo exhibits from the Cygnans' last port-of-call, some of the humans escape the starships just before the strange convoy leaves our Solar System - after securing a working example of the Cygnan annihilation drive and foiling a last-ditch espionage attempt.