The Milky Way’s spinning disk of gas and dust gives rise to graceful spiral arms, which are the galaxy’s most active star-forming sites. Now researchers using a telescope in Earth’s atmosphere have discovered a mechanism for how magnetic fields shape star birth in the dense filaments, or “bones,” that weave their way through these arms.
The new work describes how galaxy-wide magnetic fields, depending on their orientation and strength, can both funnel material from one area to another and keep out the dust and gas that make up the planets. denser regions to collapse under the effect of gravity. These processes dampen star formation; without them, we would have a much brighter night sky than we see today.
Ground-based telescope observations in 2015 confirmed the physical properties of the bones of gas and dust that lined the arms of the Milky Way. But the researchers didn’t know the precise role of magnetic fields in star-forming activity on a smaller scale. “We knew the bones existed, but at the time there was no way to map the details of their magnetic structure,” says Simon Coudé, postdoctoral researcher at Worcester State University and the Center for Astrophysics | Harvard and Smithsonian. Coudé presented the new findings at the American Astronomical Society’s 2023 winter meeting.
For this work, researchers determine the fine-scale direction of these magnetic fields by measuring the alignment of dust particles. Specifically, they quantify how magnetic properties help keep gas and dust in massive bones from collapsing to form stars. With data from the instruments onboard the SOFIA telescope carried on Boeing-747 during its last years of operation, “we were able to see the field structure in star-forming clouds over large expanses of the galaxy,” Coudé said.
A bone map from this project showed that magnetic fields tended to be perpendicular to the length of bone in dense areas of active star birth and more parallel elsewhere. This could mean that parallel fields from less dense regions are feeding into the denser material, where the fields are strong enough to limit gravitational collapse despite the additional star-forming material, the researchers say. They also found magnetic fields along other galactic bones strong enough to dampen star formation in all but the most active areas.
“We know that entire galaxies are permeated by magnetic fields. We now see the structures of these fields in the densest regions, where they are susceptible to star formation,” says Enrique Lopez-Rodriguez, an extragalactic astronomer at the Kavli Institute for Particle Astrophysics and Cosmology. Stanford University, which was not involved in the study. study. Ultimately, he adds, this will lead to understanding how the balance between gravity and large-scale magnetic fields dictates star formation at the smallest scales, in other galaxies as well as ours. .
