Magnetic Fields Slow Star Birth Near Milky Way’s Core
Webb Telescope Reveals Unexpected Structures in Galactic Center
Astronomers have uncovered a surprising reason for the sluggish star formation near the center of our galaxy: powerful magnetic fields are acting as a brake on the process. New observations from the James Webb Space Telescope reveal a complex network of plasma filaments that appear to be suppressing the birth of new stars in the Sagittarius C region.
A Star Factory in Slow Motion
Sagittarius C, located roughly 200 light-years from the supermassive black hole at the Milky Way’s heart, is a dense region brimming with gas and dust. Despite this abundance of star-forming material, star birth is surprisingly limited. Researchers from the University of Virginia, including undergraduate Samuel Crowe and astrophysicist John Bally, sought to understand this discrepancy.
The team’s investigation, utilizing the JWST’s Near-Infrared Camera (NIRCam), revealed a structure unlike anything previously observed. Instead of the expected dense gas clouds, the region is permeated by thin, glowing filaments resembling tangled spaghetti.
“This region has the highest density of stars and massive, dense clouds of hydrogen, helium, and organic molecules,”
—John Bally, Professor of Astrophysics
These filaments, composed of hot, charged particles (plasma), emit light detectable by JWST. The strongest filaments form a π-shaped structure at the region’s center, with fainter strands extending from a dense gas cloud. According to NASA, the Milky Way galaxy is expected to collide with the Andromeda galaxy in approximately 4.5 billion years, potentially triggering a burst of star formation. NASA
Invisible Forces at Play
Further analysis, incorporating data from the MeerKAT radio telescope in South Africa and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, revealed that the filaments’ radio signals originate from nonthermal sources—indicating the presence of strong magnetic fields. These fields appear to be trapping the plasma and hindering star formation.
The magnetic fields in Sagittarius C are exceptionally strong, dominating the thermal pressure even in the densest gas clouds. Crowe, who continued his research as a Rhodes Scholar, noted, “Because of these magnetic fields, Sagittarius C has a fundamentally different shape, a different look than any other star forming region in the galaxy away from the galactic center.”
A Contrast to Orion
This magnetic structure contrasts sharply with regions like the Orion Nebula, a closer and more actively star-forming area. The Orion Nebula exhibits smoother gas clouds and a much higher star formation rate, likely due to weaker magnetic fields.
Stars are born within dense molecular clouds, where gravity pulls gas and dust together until nuclear fusion ignites. However, young stars also emit radiation that disperses the surrounding gas, eventually halting further star formation. Bally explained, “Even the sun, we think, formed in a massive cluster like this. Over billions of years, all of our sibling stars have drifted away.”
Sagittarius C is nearing the end of its stellar nursery phase, with much of its gas already dispersed. In a few hundred thousand years, it may become a dark, quiescent region. These findings offer a new perspective on star formation in extreme galactic environments and could reshape our understanding of galaxy evolution.
