Stars are created when enormous cold gas clouds in space collapse due to their own gravity. However, not all gas undergoes this collapse, and not all clouds form stars with the same efficiency. A key question in astrophysics is what governs this process, with magnetic fields, which weave through interstellar gas like an unseen framework, being a prime suspect. A new study by MIT Haystack Observatory researchers, published in The Astrophysical Journal, has mapped this framework in unprecedented detail in DR21, one of the most vibrant star-forming regions within 5,000 light-years of our solar system.
The findings reveal that magnetic fields in DR21 do more than just exist; they actively influence how gas moves into the cloud’s dense core, where new massive stars are forming. “The magnetic field acts like a set of railroad tracks,” said Thushara Pillai, research scientist at MIT Haystack Observatory and lead author of the study. “Gas flows along the tracks toward the central ridge, building it up over time. Across the tracks, the field resists motion. So the field doesn’t stop star formation — it channels it.”
DR21 is part of the Cygnus X complex, a region rich with young stars and some of the Milky Way’s brightest objects. Its core structure, the DR21 Main Ridge, is a thick filament approximately 13 light-years long, containing about 20,000 times the sun’s mass in cold molecular gas. Around it is a network of smaller “sub-filaments,” previously suggested to feed material into the ridge, though no instrument had successfully traced the magnetic field from the dense ridge into these smaller structures until now.
The study utilizes data from SIMPLIFI (Study of Interstellar Magnetic Polarization: a Legacy Investigation of Filaments), a SOFIA Legacy Program led by Pillai, which includes a global team of observers, theorists, and instrument scientists from over a dozen institutions on four continents. Jens Kauffmann, also a research scientist at MIT Haystack Observatory, led the data reduction. “Working with SOFIA’s polarization data was challenging,” Kauffmann noted. “We had to characterize the data reduction systematics from scratch. But the result was worth it: a homogeneous map of the magnetic field across an entire star-forming complex, at a level of detail that no other facility could provide.”
The researchers compared the directions of the magnetic field, the local gravitational forces, and the gas structures themselves. They found that gravity and the magnetic field are remarkably aligned throughout the cloud, a sign of magnetically guided accretion, where gas flows inward along magnetic field lines toward the cloud’s mass center. The team estimates that the sub-filaments are delivering material to the Main Ridge quickly enough to form its massive core structure in about a million years.
The study also clarifies an earlier observation where gas appeared to be moving toward the central ridge slower than gravity alone would suggest. The team discovered that the magnetic field, and thus the accretion flow it directs, is nearly entirely in the plane of the sky, meaning only a small part of the actual motion is visible along our line of sight. The gas isn’t moving slowly; rather, it moves sideways across our view.
SOFIA, the Stratospheric Observatory for Infrared Astronomy, was a Boeing 747SP adapted by NASA and the German Aerospace Center to carry a 2.7-meter telescope into the stratosphere. After 12 years of service, it was retired in September 2022, and no equivalent facility is currently available or planned. “To really understand how magnetic fields shape star formation across the galaxy, we need to go further — to fainter emission, larger areas of sky, and clouds at every stage of evolution,” Pillai stated. “That requires a space-based far-infrared mission with polarization capability. We don’t have one. Building one should be a priority for the next decade of astrophysics.”
Original Source: news.mit.edu
