Big or small, dense or empty, it's one thing they all share.
Galaxies come in all shapes and size, and NASA’s best estimates indicate there are more than 200 billion of them in the observable universe. According to the latest findings from the International Centre for Radio Astronomy Research (ICRAR), all these billions of galaxies have one thing in common: They spin at a rate about about once every billion years.
“It’s not Swiss watch precision,” said Professor Gerhardt Meurer from the UWA node of ICRAR in a statement, “but regardless of whether a galaxy is very big or very small, if you could sit on the extreme edge of its disk as it spins, it would take you about a billion years to go all the way round.”
Beyond offering us all a profound sense of cosmic unity, the finding is helpful in understanding the cosmological properties of how galaxies operate. The number of stars and planets within galaxy apparently have no effect on its speed.
“Discovering such regularity in galaxies really helps us to better understand the mechanics that make them tick—you won’t find a dense galaxy rotating quickly, while another with the same size but lower density is rotating more slowly,” Meurer said.
Meurer and his team’s research also discovered that older stars lie can be found on the edges of galaxies.
“Based on existing models, we expected to find a thin population of young stars at the very edge of the galactic disks we studied,” Meurer says. “But instead of finding just gas and newly formed stars at the edges of their disks, we also found a significant population of older stars along with the thin smattering of young stars and interstellar gas.”
“So because of this work, we now know that galaxies rotate once every billion years, with a sharp edge that’s populated with a mixture of interstellar gas, with both old and young stars.”
The mechanics of galaxies are still mysterious. Even when they’re all spinning, they can still crash into each other.
Source: Popular Mechanics