How Magnetic Fields Control Galactic Growth

The Milky Way’s rotating disk of gas and dust gives rise to graceful spiral arms, which make up the galaxy’s most active star formation sites. Now researchers using an airplane-borne telescope high in Earth’s atmosphere have found a mechanism for how magnetic fields shape star birth in the dense filaments, or “bones,” that wind their way through these arms.

The new work describes how galaxy-scale magnetic fields, based on their orientation and strength, can both funnel material from one area to another and prevent the dust and gas that make up the densest regions from collapsing under gravity. These processes dampen star formation; without them, we’d have a much brighter night sky than we see today.

Ground-based telescope observations in 2015 confirmed the physical properties of the gas and dust bones that lined the Milky Way’s arms. But researchers did not know the precise role of magnetic fields in star-forming activity at smaller scales. “We knew the bones existed, but back then there was no way to map the details of their magnetic structure,” says Simon Coudé, a…