New research suggests the sun had a twin and that all stars are born in pairs. Astronomers have previously hypothesized that the sun was originally part of a stellar duo, but scientists struggled to find supporting evidence.
"We ran a series of statistical models to see if we could account for the relative populations of young single stars and binaries of all separations in the Perseus molecular cloud, and the only model that could reproduce the data was one in which all stars form initially as wide binaries," Steven Stahler, a research astronomer at the University of California, Berkeley, said in a news release. "These systems then either shrink or break apart within a million years."
Wide binaries are stellar pairs born at least 500 astronomical units apart. An astronomical unit is the distance between Earth and the sun, roughly 93 million miles.
The new findings -- detailed in the journal Monthly Notices of the Royal Astronomical Society -- confirm what a number of astronomers had previously hypothesized, that the sun began life as duo.
The sun's sibling likely escaped shortly after birth. Some researchers believe the gravity of the sun's sibling, dubbed Nemesis, pushed an asteroid into a collision course with Earth -- the asteroid that ultimately snuffed out the dinosaurs.
"We are saying, yes, there probably was a Nemesis, a long time ago," said Stahler.
Simulations designed to work out the mysteries of star formation in molecular clouds have previously suggested stars are born in pairs. The new research used computer models to analyze hard astronomical data.
Star-forming regions like the Perseus molecular cloud are littered with egg-shaped cocoons called dense cores, in which new stars are born. The latest analysis suggests stars born of theses dense cores split far apart 60 percent of the time. The other 40 percent of the time, the egg-like cores yield closely linked binaries.
The pattern explains why pairs of Perseus stars less than 500,000 years old -- Class 0 stars -- are aligned with the long axis of the dense cores and separated by at least 500 AUs. Stars between about 500,000 and 1 million years old, or Class 1 stars, are much closer and unaligned.
"As the egg contracts, the densest part of the egg will be toward the middle, and that forms two concentrations of density along the middle axis," Stahler said. "These centers of higher density at some point collapse in on themselves because of their self-gravity to form Class 0 stars. Within our picture, single low-mass, sunlike stars are not primordial. They are the result of the breakup of binaries."