In a first, Indian astronomers map magnetic field component that is key to formation of stars
For decades, astronomers have known that gravity pulls molecular clouds inward to form stars, while internal pressure pushes them outward. But in this tug-of-war, the magnetic field is the third, albeit silent player
Indian astronomers studying small molecular clouds located near the Milky Way disc have, for the first time, mapped the skeleton of the magnetic field surrounding them, providing insights into the formation of stars.
For decades, astronomers have known that gravity pulls molecular clouds inward to form stars, while internal pressure pushes them outward. But in this tug-of-war, the magnetic field is the third, albeit silent player.
As magnetic fields are invisible, the research team from Aryabhatta Research Institute of Observational Sciences (ARIES) and Assam University used the R-band polarimetry, that is, the measurement and analysis of the polarisation of electromagnetic radiation from celestial objects, to measure how starlight from distant stars becomes polarised as it passes through dust in the molecular clouds.
When starlight hits dust grains aligned by a magnetic field, the light vibrates in a specific direction. By mapping thousands of these light waves, the team "saw" the skeleton of the magnetic fields surrounding the L1604 and L121 molecular clouds for the first time, according to information shared by the Ministry of Science and Technology.
Molecular clouds are the cold and dense regions of the interstellar medium where star formation takes place. These are primarily made up of molecular hydrogen and dust and exhibit complex structures.
The researchers found two very different personalities. The two clouds also lie at very different distances from the Earth. The L1604 cloud is highly dense and more massive, and has enough material to possibly form many new stars. The L121, located toward the center of the Galaxy, is less dense and less massive than L1604, but has a stronger magnetic field.
By calculating the magnetic field strength, the scientists found that both clouds are firmly sub-critical, implying that the magnetic fields are comfortably strong enough to resist gravitational collapse across the full body of both clouds.
They found that the magnetic fields dominate the gravity and turbulence, and in the dense cores nestled deep within these clouds, gravity may be quietly gaining the upper hand, making these cores the true cradles of future star birth even as the surrounding envelope remains magnetically protected.
By showing exactly how magnetic fields wrap around and permeate these small clouds, the study reveals that magnetism is the invisible hand that slows star formation, preventing the galaxy from turning all its gas into stars at once, according to the scientists.
“L1604 and L121 are now more than just dark spots on a map; they are active laboratories where we can watch the fundamental forces of the universe, gravity and magnetism, dance in a delicate, million-year-long embrace,” they said.
