How spiral galaxies form: a realistic simulation

Astrophysicists have made the first realistic simulation of the formation of our home galaxy, the Milky Way. They've named it after Eris, the Greek goddess of strife and discord, because of the decades of debate in the field about the formation of spiral galaxies.

Simulating spiral galaxies such as the Milky Way is important in confirming that researchers understand the underlying physical laws of the universe. However, all previous attempts to recreate the formation of spiral galaxies like the Milky Way faltered on one of two points: either the simulated spiral galaxies displayed too many stars at the center or the overall stellar mass was several times too big.

This simulation, shown here in a video, is the most accurate thus far. From it, researchers have predicted that the ratio of cold dark matter to matter must be 1:6, not 1:9 as previously assumed, and that there must be  stars and gases in the outer halo of the Milky Way six hundred thousand light years away, which have not yet been observed.

The simulation shows almost the entire genesis of a spiral galaxy. Its origins date back to less than a million years after the Big Bang. The galaxy has 790 billion solar masses and comprises 18.6 million particles, from which gases, dark matter and stars form.

A research group jointly run by Lucio Mayer (see an interview here), an astrophysicist at the University of Zurich, in Switzerland, and Piero Madau, an astronomer at University of California at Santa Cruz, USA, will be publishing their results in the Astrophysical Journal.

They used a Cray XT5 “Monte Rosa” at ETH Zurich’s Swiss National Supercomputing Center (CSCS) and the NASA Advanced Supercomputer Division’s Pleiades. A regular PC would have needed 570 years for the calculations.

“Our result shows that a realistic spiral galaxy can be formed based on the basic principles of the cold dark matter paradigm and the physical laws of gravity, fluid dynamics and radiophysics,” Mayer said in a statement from the CSCS.