The Corkscrew Galaxy: A Curved Jet as a Key to Magnetic Fields
At the heart of a distant galaxy lies a "cosmic corkscrew"—a twisted jet of plasma. Astronomers noticed that radio waves passing through this spiral change their polarization slightly in a rhythmic pattern, like an echo in a winding corridor. This lets them figure out just where the magnetic field is concentrated in or around the jet. Could such a corkscrew become a tool for probing the invisible magnetic fields of entire galaxy clusters?
In a distant galaxy nicknamed the Corkscrew Galaxy, a powerful stream of particles—a radio jet—shoots out from its center. It’s not straight but wiggles like a flexible garden hose under water pressure. This galaxy, like all distant objects, is moving away from us due to the expansion of the Universe, first noticed by Edwin Hubble. The jet emits radio waves, and their polarization—the direction in which the light oscillates—reacts to magnetic fields along the way. A light ribbon tied to a garden hose turns in the wind. Here, polarization turns under the influence of magnetic fields, like a weather vane.
Astronomers mapped Faraday rotation—that’s what this twist is called—along the entire jet. It turned out that the rotation varies with the same period as the bends of the jet itself! In the eastern part, the rotation precisely follows the bends—meaning the magnetic field lives in the jet itself or its sheath. But in the western part, the connection is weak, and there the magnetic field of the intergalactic medium rules—the hot gas that fills the galaxy cluster. This gas consists mainly of hydrogen and helium; its mass, sometimes measured via gravitational lensing, is much greater than the mass of the galaxies themselves, and some of that mass is invisible dark matter—a mysterious substance discovered by Fritz Zwicky.
This method is reminiscent of using a river’s bends to measure hidden underground currents. The spiral jet works like a natural probe, letting us tell apart where the magnetic field comes from. Such observations were made possible by the ASKAP radio telescope, which captures the slightest polarization twists. These twists depend on the properties of the gas and the magnetic field, and calculations always factor in the constant speed of light, whose discovery is tied to the work of James Clerk Maxwell. Scientists hope that in the future, with the launch of the giant SKA radio telescope, they will find many such corkscrews and build a detailed map of magnetic fields across the entire Universe. This will help us better understand how clusters grow, how new galaxies are ignited within them, and what role black holes play at their centers.
🎯 This galaxy earned the nickname 'Corkscrew Galaxy' for a reason: its radio jet is twisted like a screw thread and stretches for hundreds of thousands of light-years.