Astronomers have taken their clearest look yet at how some of the biggest stars in our galaxy are born—and it turns out the process is a cosmic battle between two powerful forces: gravity and magnetism.
A research team led by Dr. Qizhou Zhang at the Center for Astrophysics | Harvard & Smithsonian used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to study 17 different star-forming regions.
These are giant clouds of gas and dust where clusters of massive stars emerge.
With ALMA’s extraordinary sensitivity, the team was able to zoom in on these regions to scales of just a few thousand astronomical units—about ten times the distance from the Sun to Pluto.
Their goal was to understand how invisible magnetic fields interact with gravity as clouds collapse to form stars.
For decades, scientists have debated which force has the upper hand. Gravity pulls gas inward, making it denser and hotter until stars are born. But magnetic fields, along with turbulence, push back against this collapse.
The new ALMA observations show, for the first time on a large scale, how this struggle actually plays out. At first, magnetic fields resist gravity, holding gas back.
But as gas grows denser, gravity starts to overpower magnetism. In fact, the magnetic fields themselves get dragged into alignment with the flow of gas, showing that gravity eventually takes control.
Interestingly, the study also found that magnetic field lines are not randomly oriented. Instead, they often fall into two patterns: sometimes they line up with gravity, and other times they remain perpendicular to it.
This reveals a more complex and evolving relationship than scientists expected, suggesting that magnetic fields still influence how gas collapses, even while gravity dominates the final stages.
“This is the first time we’ve been able to statistically track how magnetic fields change as a cloud collapses to form stars,” said Zhang. “ALMA’s ability to see these regions in such detail lets us uncover how gravity can actually reshape magnetism itself.”
Understanding how stars form is crucial to many areas of astronomy. The birth of stars sets the stage for the creation of planets, the evolution of galaxies, and even the history of our own Sun. By showing how magnetic fields and gravity interact, this research settles a long-standing debate and gives scientists new ways to test theories about cosmic origins.
As the largest ALMA polarimetric survey ever done, the project sets a new benchmark for studying the hidden structures inside star-forming clouds.
The conclusion is clear: magnetic fields matter—but in the end, gravity is the ultimate force that shapes the birth of the most massive stars.
