Free Astronomy Magazine January-February 2026

45 JANUARY-FEBRUARY 2026 T his image from NASA’s Spitzer Space Telescope shows a star formation re- gion in molecular cloud NGC 6334, also known as the Cat's Paw Nebula. The colors correspond with emission at 3.6 microns (blue), 4.5 microns (green), and 8 microns (red). This cloud is actively forming massive stars, and is located in the constellation Scorpius, between 4,200 to 5,500 light-years from Earth. ALMA data overlaid on the image shows details of four specific areas that were ob- served (NGC6334I, NGC6334I(N), NGC6334IV and NGC6334V), revealing invisible forces of magnetism and gravity as they wrestle and shape the formation of stars deep within the giant molecular cloud. The color scale in the ALMA images represents the intensity of the dust emission at 1.3mm and the drapery lines rep- resent the orientation of the magnetic field. [Background, NASA/JPL-Caltech; overlay: ESO/NAOJ/NSF NRAO; image created by NSF/AUI/NSF NRAO/M. Weiss] ten trillion times greater than what’s typically found in interstellar clouds. But this epic collapse isn’t driven by gravity alone—magnetic fields and turbulence both push back, resisting the pull. For decades, astronomers have de- bated which force dominates as gas clouds shrink and stars ignite. New ALMA observations by Zhang’s team have provided crucial an- swers. By measuring how the direc- tions of magnetic fields change at different distances from young pro- tostars, the researchers found that as gas becomes denser, gravity be- gins to win this cosmic tug-of-war. Magnetic fields, which start out mainly resisting gravity, are gradu- ally pulled into alignment with in- falling gas, showing a clear sign that gravity takes over as the lead- ing force shaping the collapsing cloud. This study marks the first time astronomers have statistically traced how magnetic fields behave as gravity pulls a star-forming cloud inward at precise measurements, in thousands of astronomical units, across a large sample of massive cluster-forming regions. The findings revealed a surprising pattern: the magnetic field orienta- tions do not just occur randomly. Instead, they show two prefer- ences: sometimes lining up with the direction of gravity, or sometimes perpendicular—evidence for a com- plex and evolving relationship be- tween these two cosmic forces. “With ALMA’s extraordinary sensi- tivity and resolution, we can now probe these cosmic birthplaces in unprecedented detail,” said Zhang. “We see that gravity actually reori- ents the magnetic field as clouds collapse, offering new clues about how massive stars—and the clusters they inhabit—emerge from the in- terstellar medium.” Understanding how stars form is fundamental to almost every field of astronomy, shaping everything from the ori- gins of our own Sun to the evolu- tion of galaxies. This work not only settles long- standing debates about the relative importance of magnetic fields and gravity in massive star formation, but also gives scientists powerful new tools to test and refine theo- ries about the life cycles of stars, planets, and cosmic clouds. As the largest ALMA polarimetric study of its kind, this project sets a new standard for understanding both the visible and invisible compo- nents of our galaxy. The results re- veal that while magnetic fields shape star-forming clouds, gravity ultimately takes the lead in birth- ing the most massive stars—an in- sight made possible by ALMA’s cut- ting-edge technology. Smithsonian used the Atacama Large Millimeter/submillimeter Ar- ray (ALMA) to conduct the largest and most detailed survey to date of magnetic fields in 17 regions where clusters of massive stars are form- ing. These observations, reaching down to just a few thousand astro- nomical units (about 10 times the distance from the Sun to Pluto) offer the first statistical insight into how the invisible forces of magnet- ism and gravity wrestle and shape the formation of stars deep within giant molecular clouds. Star forma- tion requires gas in space to be squeezed to densities more than ! NGC 6334