In a new study published in the journal Astronomy & Astrophysics, Dr. Juan Soler of the Max Planck Institute for Astronomy used observations from ESA’s Herschel and Planck space observatories to delineate the role of magnetic fields in star-forming molecular cloud structure.
This composite image shows the Orion A molecular cloud, the nearest known massive star factory, as seen by ESA’s Herschel and Planck space observatories. Located approximately 1,630 light-years away, Orion A is one of the two giant molecular clouds in the Orion molecular cloud complex. The other cloud is Orion B, which lies east of Orion’s Belt. Orion A is packed full of gas — it contains so much material, in fact, that it would be capable of producing tens of thousands of Sun-mass stars. Different colors visible here indicate the light emitted by interstellar dust grains mixed within the gas, as observed by Herschel at far-infrared and sub-millimeter wavelengths, while the texture of faint gray bands stretching across the frame, based on Planck’s measurements of the direction of the polarized light emitted by the dust, show the orientation of the magnetic field. Image credit: ESA / Herschel / Planck / J.D. Soler, Max Planck Institute for Astronomy.
The space that sits between stars is not empty but is instead filled with a cool substance known as the interstellar medium, a mix of gas and dust that often clumps together.
When these clumps become dense enough they start to collapse under their own gravity and become hotter and denser until they spark something exciting: the creation of new stars.
Magnetism is an important component of the interstellar medium.
Magnetic fields permeate the Universe, and are involved in helping clouds of matter maintain the delicate balance between pressure and gravity that eventually lead to the birth of stars.
The mechanisms that oppose the gravitational collapse of star-forming clouds remain somewhat unclear, but the new research suggests that interstellar magnetic fields play a significant role in guiding the flows of matter in the interstellar medium, and may be a key player in preventing interstellar cloud collapse.
Dr. Soler used Herschel and Planck data to study ten nearby — at distances of up to 1,500 light-years — star-forming clouds.
He found that matter within the interstellar medium is coupled to the surrounding magnetic field and can only move along its lines, creating a sort of ‘conveyor belts’ of field-aligned matter, as expected from the effect of electromagnetic forces.
When these interact with an external source of energy — such as an exploding star, or other material moving through the galaxy — these flows along the magnetic field lines converge.
The process creates a compressed pocket of higher density that appears to be perpendicular to the field itself.
As more and more matter streams inwards, this region becomes increasingly dense, until it eventually reaches the critical density for gravitational collapse and crumples in on itself, leading to the formation of stars.
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Juan D. Soler. 2019. Using Herschel and Planck observations to delineate the role of magnetic fields in molecular cloud structure. A&A 629, A96; doi: 10.1051/0004-6361/201935779
