Scientists have imagined space dust for decades as tiny dancers spinning in starlight. They whispered secrets about the universe.
Astronomers caught the interstellar grain in mid-twirl. The grains are just micrometers across and align with magnetic fields as if they were compass points.
The silicate rich specks do more than just float. They shape stars, polarize the starlight and reveal invisible galactic magnetic threads.
Since 1949, astrophysicists have been puzzled by their strange alignment. This new evidence helps us to understand their magnetic movements and what they have been saying all along.
Scientists have known for years that cosmic dust is responsible for polarizing starlight, causing its electric field to be pushed in a certain direction. Scientists suspected that these tiny grains of silicate, which were oddly-shaped, aligned with the magnetic fields running through space like invisible lines traced by iron filings.
The how of this cosmological choreography was a mystery.
A team from the Indian Institute of Astrophysics, Bengaluru has now cracked the code. These observations provide the strongest evidence yet that dust grains in interstellar space align perfectly with magnetic fields.
In the Milky Way galaxy, at 12,000 light years from Earth, is a cosmic cloud: G34.43+0.24, where dust and gas are forming into thick clouds of stars.
Astronomers in Hawaii used the POL-2 Polarimeter to zoom in on this stellar maternity ward. What did they discover? What did they find?
Scientists have discovered three different ways that space dust reacts to magnetism and light in a cloud forming stars:
RAT-A is the first, where uneven starlight makes non-spherical grain spin, aligning magnetic fields like small cosmic compasses. Radiative Torque Disruption (RAT-D) is a process whereby intense radiations from new stars cause some grains to spin so quickly that they break into pieces, thereby weakening the magnetic signal. Finally, M-RAT (Magnetically-enhanced Radiative Torque Alignment) gives grains a magnetic boost, helping them align more efficiently and shine with stronger polarization.
The discovery shows that the grains of cosmic dust are not passive, but rather perform on a stage of magnetic fields. According to their surroundings, they may align beautifully, crumble when under pressure or be hyper-efficient magnetic field tracers.
Astronomers can now map the invisble scaffolding of our Galaxy with greater precision by catching the alignment mechanisms at work. This breakthrough is important because magnetic fields influence everything, from galactic structure to star formation.
This work provides a strong observational basis for popular theories of grain alignment and is a major contribution to our long-standing search to better understand grain alignment mechanisms.” Saikhom Pravash is a PhD researcher and lead author at IIA Pondicherry University.
Understanding dust alignment, as co-author Archana Soam from IIA adds: It’s crucial to trace interstellar fields and explore their influence on the formation of stars.
Journal Reference
- Saikhom Pravash (Le Ngoc Tram), Archana Diep (Pham Ngoc Diesp), Thiem H Hoang (Nguyen Bi Ngoc), and Nguyen Ngoc Ngoc. The B-fields in Interstellar Filaments and Dust Using Dust Polarization. III. Grain Alignment Mechanisms and Disruption in G34.43+0.24 using Polarization observations from JCMT/POL-2. The Astrophysical Journal. DOI 10.3847/1538-4357/adae06
