In an airplane, air movements on both small and large scales contribute to turbulence, which can lead to a bumpy flight. Turbulence on a much larger scale is important for the formation of stars in the giant molecular clouds that pervade the Milky Way.
In a new study funded by NASA and published in the journal Science Advances, scientists created simulations to investigate how turbulence interacts with cloud density. Clumps, or density pockets, are places where new stars are born. Our Sun, for example, was formed 4.6 billion years ago in a clumpy part of a cloud that collapsed.
“We know that the main process that determines when and how fast stars form is turbulence, because it gives rise to the structures that create stars,” says Evan Scannapieco, professor of astrophysics at Arizona State University and lead author of the study. “Our study reveals how these structures form.”
Giant molecular clouds are full of random, turbulent motions that are caused by gravity, stirring of galactic arms, winds, jets, and explosions of young stars. This turbulence is so strong that it creates jolts that cause changes in density in the cloud.
The simulation used points called tracker particles that cross the molecular cloud and move with the material. As they move, the particles record the density of the part of the cloud they encounter, creating a history of density changes over time. The researchers, who also included Lubin Pan of Sun Yat-sen University in China, Markus Bruggen of the University of Hamburg in Germany, and Ed Bui II of Vassar College in Poughkeepsie, New York, simulated eight scenarios, each with its own set of realistic cloud properties.
The team found that the acceleration and deceleration of shock waves plays an important role in the path of particles. Shock waves slow down when they hit a high-density gas and speed up when they hit a low-density gas. This is similar to the way an ocean wave intensifies when it hits shallow water near the shore.
When a particle is hit by a shock wave, the area around it becomes denser. But because shock waves slow down in dense regions, once the clumps become dense enough, turbulent motions cannot make them even denser. These densest high-density regions are where stars are most likely to form.
While other studies have examined the molecular structures of cloud density, this simulation allows scientists to see how these structures form over time. This helps scientists understand how and where stars are likely to be born.
“We can now better understand why these structures look the way they do because we can track their history,” Scannapieco said.
The post NASA study examines turbulence in molecular clouds first appeared on HiTechExpert.top.