From planets to stars to galaxies, celestial things frequently spin. According to study co-author Noam Libeskind, a cosmologist at Germany's Leibniz Institute for Astrophysics Potsdam, large clusters of galaxies usually rotate very slowly, if at all. Many scientists believed that this was the limit of spinning on cosmic scales.
But in the new research, Libeskind and his colleagues found that cosmic filaments, or gigantic tubes made of galaxies, apparently spin. “There are structures so vast that entire galaxies are just specks of dust,” Libeskind said. “These huge filaments are much, much bigger than clusters.”
Previous study revealed that after the Big Bang 13.8 billion years ago, much of the gas that makes up the majority of known matter in the universe collapsed to form colossal sheets. These sheets then broke into the filaments of a vast cosmic web.
The scientists examined over 17,000 filaments using data from the Sloan Digital Sky Survey, analyzing the rate at which the galaxies that make up these gigantic tubes move within each tendril. The researchers discovered that the way these galaxies moved indicated that they were rotating around the central axis of each filament.
The fastest the researchers saw galaxies whirl around the hollow centers of these tendrils was about 223,700 mph (360,000 kph). The scientists noted that they do not suggest that every single filament in the universe spins, but that spinning filaments do seem to exist.
The big question is, “Why do they spin?” Libeskind said. The Big Bang would have given the universe no primordial spin. As such, whatever caused these filaments to spin must have originated later in history as the structures formed, he said.
One possible explanation for this rotation is that as the powerful gravitational fields of these filaments pulled gas, dust and other material within them to collapse together, the resulting shearing forces might have spun up this material. Still, right now, “we’re not really sure what can cause a torque on this scale,” Libeskind said.
Scientists are now attempting to explain the origin of filament spin using computer simulations of how matter behaves on the biggest cosmological scales.
Reference(s): Nature Astronomy