Astronomy textbooks have long told neophyte stargazers that three of every five points of light in the night sky are waltzing pairs of stars called binary systems. The statistic is based on counts of visible stars begun at the turn of the 20th century, when telescopes were less powerful. Brighter stars are relatively rare, though: in our galaxy, they account for 15 to 20 percent of the stellar systems. In the past five years, more sensitive instruments have surveyed red dwarf systems, which are dimmer and much more common. So far only a quarter of these systems were found to be binary, which would mean that two thirds of stellar systems are actually single red dwarfs. The result should help researchers make sense of star-formation theories, says Charles Lada of the Harvard-Smithsonian Center for Astrophysics, who reports the tally in an upcoming Astrophysical Journal Letters. “Many of the current theories find it a lot easier to form single stars,” Lada says.
This article was originally published with the title "Singular Is the New Binary" in Scientific American 294, 4, 32 (April 2006)