The First Stars Were in Binary Systems

Experts from the US Department of Energy's (DOE) SLAC National Accelerator Laboratory, the Michigan State University, and the Stanford University have recently managed to use computer models to simulate the way in which the first twin stars in the very early Universe were formed. Stretching as far back as 200 million years after the Big Bang, the model reveals the Population III stars – the name given to early inhabitants of the Cosmos – were not nearly as massive as first suggested, and also that they may have originally formed in binary star systems, and not by themselves.

“For a long time the common wisdom was that these Population III stars formed alone. Researchers also have believed that these stars were incredibly massive – up to 300 times the size of our own sun. Unfortunately, the observations just didn't jibe with the simulations we created,” MSU Assistant Professor of Physics and Astronomy Brian O'Shea, who also holds an appointment with the University's Lyman Briggs College, says.

“We used to think that these stars formed by themselves, but now we see from our computer simulations that sometimes they have siblings. These stars provide the seeds of next generation star formation, so by understanding them we can better understand how other stars and galaxies formed,” Astrophysicist Matthew Turk, an expert at the Kavli Institute for Particle Astrophysics and Cosmology, adds. The research facility is a joint institute of Stanford University and the SLAC National Accelerator Laboratory, initiated by a grant from Fred Kavli and the Kavli Foundation.

Using data of the Cosmic Microwave Background (CMB), collected by science missions in space, the experts were able to insert a large variety of simulation parameters into their new computer model, including primordial gas and dust, as well as some amounts of dark matter. Some of the simulations were so complex, that they covered more than 400 quadrillion cubic miles of volume, and required weeks to run on the team's computers.

“We ran five of these calculations starting from the beginning of the universe, and to our surprise one of them was special. This opens a whole new realm of research possibilities. These stars could evolve into two black holes, which could have created gravitational waves we could detect with an instrument like the Laser Interferometer Gravitational Wave Observatory and, if they fall into bigger black holes, for the Laser Interferometer Space Antenna. Or one of the stars could evolve into a black hole that could create gamma-ray bursts that we could detect with the Swift mission and the Fermi Gamma-ray Space Telescope,” Tom Abel, also from the Kavli Institute, says.

“All of the earlier simulations suggested that when these stars formed they were single, massive stars. But now we have faster computers, and we're able to work out our models to a higher level of detail. Our new simulations found that when you actually resolve everything it is possible that once the gas was going to make the stars, it was bound together tightly enough to make binary stars,” O'Shea concludes.