How Invisible Magnetic Fields Help Decide When a Star Is Born

Scientists have uncovered fresh evidence showing that magnetic fields play a crucial role in the birth of stars, shaping how clouds of gas collapse or fail to collapse into new stellar objects. Astronomers from the Indian Institute of Astrophysics (IIA) studied a star-forming region called the L328 molecular cloud, located about 700 light years away. Their research reveals that magnetic fields remain well organised and connected across vast distances, from the scale of entire clouds down to the tiny cores where stars begin to form.

A closer look at star nurseries

Stars are born inside molecular clouds cold, dense regions of gas and dust. Whether these clouds turn into stars depends on a delicate balance between gravity, turbulence, heat, and magnetic fields. While gravity pulls material inward, magnetic fields and turbulence can slow or even stop this collapse. To understand this process better, researchers mapped magnetic fields at different scales within L328. Using polarisation data, they were able to trace the direction and strength of magnetic fields from large cloud structures down to the heart of a collapsing core.

A rare, quiet protostar

The team focused on a special region called S2, which hosts a very faint protostar known as a Very Low Luminosity Object (VeLLO). Because this young star produces weak outflows, it causes little disturbance in its surroundings. This makes it an ideal natural laboratory to study magnetic fields that existed even before star formation began. Observations were carried out using the POL-2 instrument on the James Clerk Maxwell Telescope, which detects polarised light emitted by dust grains aligned with magnetic fields.

Stronger fields, smaller regions

The results show that magnetic fields become stronger as scientists move closer to the dense core where a star is forming. The fields remain neatly aligned across all scales studied, suggesting they actively guide the collapse of material rather than being randomly tangled.

Energy calculations reveal that magnetic forces and turbulence are just as powerful as gravity and far stronger than simple heat effects. This means magnetic fields can significantly influence whether a cloud core collapses into a star or remains starless.

Why this discovery matters

The study, published in the Monthly Notices of the Royal Astronomical Society, helps explain why star formation in the universe is surprisingly inefficient. Some cloud cores may be held up by strong magnetic support, preventing gravity from doing its job. In essence, the research shows that star birth is not driven by gravity alone. Invisible magnetic fields quietly shape the fate of stellar nurseries, deciding where stars will shine and where they never will.