Free Astronomy Magazine November-December 2026

and wider, slower outflows — a process astronomers have long sus- pected is shaped and powered by magnetic fields twisted into a fun- nel-like, ring shape around the jet. “For the first time, these ALMA ob- servations have captured this invisi- ble funnel of magnetic fields,” said Ching, “This is exciting because it proves a decades-old theory about how stars, like our own Sun, are born and fire off powerful cosmic jets.” The team used ALMA’s exceptional resolving power, roughly 30 times sharper than that of earlier tele- scopes, to measure the faint polar- ization of carbon monoxide gas radiating from the outflow around IRAS 4A. That polarization signal let the researchers trace the morphol- ogy and strength of the magnetic field threading through the outflow at distances of only a few hundred astronomical units (the average dis- tance between the Earth to the Sun) from the young star. The team found the magnetic field measured a few thousandths of a gauss (modest compared to a house- hold magnet, but immense on the scale of interstellar space) and that it wrapped around the outflow like a coil, running perpendicular to the direction the gas was flowing and matching the outflow’s rotation. That geometry is the signature of a “toroidal” (or ring-shaped) mag- netic field, exactly what theoretical models have predicted for decades — but never directly confirmed at this level of detail. “This study represents the first and most high-resolution observation of milligauss-strength toroidal mag- netic fields at a scale of several hun- dred astronomical units from a protostar,” adds Ching. “We knew that IRAS 4A was a text- book case: 20 years ago, in a work published in Science, we found that this region followed the theoreti- cally expected magnetically driven collapse” , says Josep Miquel Girart, co-author and researcher at the In- stitute of Space Sciences (ICE-CSIC) and the Institute of Space Studies of Catalonia (IEEC). The team also uncovered an unex- pected bonus: a straightforward mathematical relationship, based on the physics principle known as Am- père’s law, linking the twisting of the magnetic field to the electric currents flowing through the gas. Because that relationship follows a predictable, linear pattern, it gives astronomers a new and more direct way to work out the direction of magnetic fields in the clouds of gas and dust where stars are born — a notoriously difficult measurement to make. Understanding how magnetic fields shape stellar outflows helps as- tronomers explain a fundamental step in star formation, for how young stars shed excess material and angular momentum so they can con- tinue growing, rather than spinning themselves apart. The same physical process is thought to play out at vastly different scales throughout the Universe, from newborn stars like the one studied here, to the su- permassive black holes that power distant galaxies. NOVEMBER-DECEMBER 2026 T his artist’s illustration shows the twisted, funnel-shaped magnetic field (rep- resented by white spiral lines) that ALMA detected wrapped around the gas outflow streaming from a young star embedded in the NGC 1333 IRAS 4A. New data revealed this ring-shaped structure in unprecedented detail, confirming a decades-old prediction of how magnetic fields launch and shape powerful jets from young stars. [NSF/AUI/NSF NRAO/M. Weiss] !