An Astrophysicist Says Isaac Asimov's Legendary Sci-Fi Planet 'Kalgash' Could Be Real
Isaac Asimov's 1990 novel Nightfall takes place on Kalgash, a planet illuminated by a ring of stars that only sees nightfall once every 2049 years. It was named the best science-fiction short story of all time by the SFWA in 1964, but the question that's been fascinating astrophysicists like Sean Raymond is whether a planet like Kalgash could ever exist.
It turns out the answer is yes—all it takes is eight stars, a black hole, and a couple well-placed moons.
First, a little backstory of Nightfall.
Apparently, the idea came to Asimov after reading a Ralph Waldo Emerson quote: "If the stars should appear one night in a thousand years, how would men believe and adore, and preserve for many generations the remembrance of the city of God!"
When he mentioned this to John W. Campbell, the founder of Astounding Stories, Campbell had a different take on what would happen: "I think men would go mad." This is the route Asimov takes in his story: when night finally falls on Kalgash, it causes widespread insanity across the planet due to the psychological shock, and precipitates the destruction of civilization.
Sean Raymond fell in love with this story, but he wanted to know if Kalgash's (known as 'Lagash' in the short story version) perpetual daylight could happen in a real-life star system. After modeling many different configurations, he found that several potential systems could create the right effect. One system involves a ring of eight equally spaced sun-like stars orbiting a large black hole, with another red dwarf star orbiting inside the ring and an Earth-like planet orbiting the red dwarf. Another system involves two rings of stars orbiting a black, with an Earth-like planet orbiting between the two rings. These configurations would create perpetual daylight, but the additions of appropriately sized moons could create solar eclipses that would mimic the rare periods of darkness Asimov described in Nightfall.
If all this sounds implausible to you, consider that the scientists of Kalgash have trouble believing a planet with a daily night cycle could exist: one of the astronomers in the story claims "life would be impossible on such a planet. It wouldn't get enough heat and light, and if it rotated there would be total darkness half of each day. You couldn't expect life—which is fundamentally dependent on light—to develop under those conditions."
Funny stuff, Asimov.