Heart of the Sun (Star Trek: The Original Series #83)

When an abandoned space habitat is found within a distant asteroid belt, the Starship Enterprise is sent to investigate. Captain Kirk and his crew discover an artificial world full of technological marvels – and unexpected dangers. But wonder and curiosity soon give way to fear when the habitat suddenly sends itself on a collision course with the system's sun, with Spock inside! Now Kirk and crew must find a way to save a planet, and a friend, without destroying the treasure trove of alien science, and time is running out...