How Some Breathtaking Disk Galaxies Get Their Spiraling Arms (Video)
Spiraling disk galaxies are some of the most beautiful and photogenic cosmic residents of the universe. With their bright center and outer arms, they can create images that are breathtaking. In fact, our Milky Way is a spiral, housing Earth and our solar system near one of its own arms.
But how exactly do these galaxies get their arms in the first place, and how do they maintain them? The questions have puzzled astrophysicists for years. Yet now, new research has revealed exactly how these galaxies get their awe-inspiring shapes.
There have been two dominate theories about the origin and fate of the arms in disk galaxies. The first is that these arms come and go over time. The second theory, which is more widely accepted, is that the material that makes up the arms, which includes stars, gas and dust, is affected by differences in gravity and jams up. This phenomenon helps sustain the arms for longer periods.
In order to more fully examine these spiral shapes and to find out if either of the theories was correct, the researchers used powerful new computer simulations. These simulations followed the motions of as many as 100 million "stellar particles" as gravity and other astrophysical forces sculpted them into familiar galactic shapes. In particular, the study modeled stand-alone disk galaxies, which are ones that are not influenced by another nearby galaxy or object.
"We show for the first time that stellar spiral arms are not transient features, as claimed for several decades," said one of the researchers, Elena D'Onghia, in a press release. "The spiral arms are self-perpetuating, persistent and surprisingly long lived."
In fact, the new results suggest that the arms arise as a result of the influence of giant molecular clouds, which are star forming regions or nurseries that are common in galaxies. These clouds act as "perturbers" and can initiate the formation of spiral arms and then sustain them indefinitely.
The new study shows not only the origins of these structures, but the fact that they're not likely to disappear any time soon. It also gives scientists a better understanding for future research about these galaxies.
The findings are published online in The Astrophysical Journal.