"Isaac Asimov's 'Nightfall' tells the story of a civilization on a planet with six suns, where night comes only once every 2,049 years. Scholars of that world have uncovered traces of at least nine previous cultures, all of which reached a height comparable to their own and then vanished suddenly. Because of their viewing handicap, those scientists cosmology is faulty. At their most creative, they can imagine that their universe consists of perhaps a few dozen 'stars' -- mysterious lights that eccentric cultists are always talking about. When night does fall and myriad stars shine forth, their cosmology, and indeed the philosophical basis for their society, crumbles." -- Anthony L. Peratt, physicist, February 1992
Science Daily: First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Sextuplet System.
ScienceDaily (Dec. 13, 2009) — In ancient times, people with exceptional vision discovered that one of the brightest stars in the Big Dipper was, in fact, two stars so close together that most people cannot distinguish them. The two stars, Alcor and Mizar, were the first binary stars -- a pair of stars that orbit each other -- ever known.
Modern telescopes have since found that Mizar is itself a pair of binaries, revealing what was once thought of as a single star to be four stars orbiting each other. Alcor has been sometimes considered a fifth member of the system, orbiting far away from the Mizar quadruplet.
Now, an astronomer at the University of Rochester and his colleagues have made the surprise discovery that Alcor is also actually two stars, and is apparently gravitationally bound to the Mizar system, making the whole group a sextuplet. This would make the Mizar-Alcor sextuplet the second-nearest such system known. The discovery is especially surprising because Alcor is one of the most studied stars in the sky.
"Finding that Alcor had a stellar companion was a bit of serendipity," says Eric Mamajek, assistant professor of physics and astronomy at the University of Rochester, and leader of the team that found the star. "We were trying a new method of planet hunting and instead of finding a planet orbiting Alcor, we found a star."