Nightfall is definitely one of my favourite short Sci-Fi stories of all time. You can download the short-story as a podcast here.
“Of the six suns, only Beta is left in the sky. Do you see it?”
The question was rather unnecessary. Beta was almost at zenith, its ruddy light flooding the landscape to an unusual orange as the brilliant rays of setting Gamma died. Beta was at aphelion. It was small; smaller than Theremon had ever seen it before, and for the moment it was undisputed ruler of Lagash’s sky.
Lagash’s own sun, Alpha, the one about which it revolved, was at the antipodes, as were the two distant companion pairs. The red dwarf Beta — Alpha’s immediate companion — was alone, grimly alone.
Aton’s upturned face flushed redly in the sunlight. “In just under four hours,” he said, “civilization, as we know it, comes to an end. It will do so because, as you see, Beta is the only sun in the sky.” He smiled grimly.
“Print that! There’ll be no one to read it.”
The wiki explains:
“Nightfall” is a science fiction short story by Isaac Asimov, about the coming of darkness to the people of a planet ordinarily illuminated at all times on all sides. It was later adapted into a novel. Nightfall has been anthologized forty-eight times, and has appeared in six collections of Asimov’s stories. In 1968, the Science Fiction Writers of America voted Nightfall the best science fiction short story written prior to the establishment of the Nebula Awards in 1965 and included it in The Science Fiction Hall of Fame Volume One, 1929-1964.