Newswise – The first laboratory investigation of the ancient, previously unconfirmed theory of the puzzling formation of planets, stars and supermassive black holes has been produced by spinning surrounding material at the US Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL). This startling confirmation culminates more than 20 years of experimentation at PPPL, the national laboratory dedicated to the study of plasma sciences and fusion energy.
The mystery arises because matter orbiting a central body does not simply fall into it, due to the so-called conservation of angular momentum that keeps the planets and Saturn’s rings from falling out of their orbits. That’s because the outward centrifugal force counterbalances the inward pull of gravity on the orbiting matter. However, clouds of dust and plasma called accretion disks that swirl around and collapse into celestial bodies do so in defiance of conservation of angular momentum.
solve the puzzle
The solution to this puzzle, a theory known as standard magnetic instability (SMRI), was first proposed in 1991 by then-University of Virginia theorists Stephen Balbus and John Hawley. They built on the fact that in a fluid that conducts electricity, whether it is a liquid of plasma or liquid metal, magnetic fields act like springs that connect different sections of the fluid. This allows the omnipresent Alfvén waves, named after Nobel laureate Hannes Alfvén, to create a force back and forth between the inertia of the vortex fluid and the magnetic field quadrant, causing angular momentum to transfer rapidly between different sections of the disk.
SMRI theory says that this strong instability shifts the plasma toward a more stable configuration. This shift pushes the angular momentum of the orbital sustainer outward toward the edge of the disk, freeing the interiors from collapsing over millions of years into encircling celestial bodies, turning planets and stars into the night. This process has been numerically verified, but has not yet been experimentally or observationally demonstrated.
said physicist Yin Wang, lead author of two recent papers, one of them in September in Material Review Letters (PRL) and a Nature Communications A paper published in August which details a joint experimental, numerical, and theoretical confirmation. Recent results from a new MRI device developed in the lab, “It successfully detected the SMRI signature,” Wang said. Co-authors on the papers are physicists Eric Gilson and Fatemeh Ebrahimi from PPPL.
“This is great news,” said Stephen Balbus, one of the developers of the theory. “Now being able to study this in the lab is a wonderful development, both for astrophysics and for the field of magnetohydrodynamics in general.
The MRI device, initially devised by physicists Hantao Ji of PPPL and Jeremy Goodman of Princeton University, both co-authors of these papers, consists of two concentric cylinders rotating at different speeds, creating a flow that simulates a vortex accretion disc. The experiment spun galinstan, a liquid metal alloy surrounded by a magnetic field. The covers that close the top and bottom of the cylinders rotate at an average speed, which contributes to the experimental effect.
The physicists are now planning new experimental and numerical studies to further characterize the reported SMRI. One study will test the critical external shift of angular momentum by measuring the rotational velocity of a liquid metal with magnetic field dimensions and the correlations between them.
“These studies will advance the emerging field of interdisciplinary laboratory astrophysics,” Wang said. “It shows how astrophysics can be done in laboratories to help solve problems that space telescopes and satellite missions can’t tackle alone, which is a huge achievement for laboratory research.”
Support for this breakthrough comes from NASA, the Department of Energy and the National Science Foundation (NSF) as a joint project between the Princeton Division of Astrophysical Sciences and PPPL. The research has benefited greatly over the years from NSF and DOE support for a collaboration between the NSF Physics Frontier Center for Magnetic Self-Organization, the Max-Planck Princeton Center for Fusion Physics and Astro Plasma.
PPPL, at Princeton University’s Forrestal Campus in Plainsboro, NJ, is dedicated to creating new knowledge about the physics of plasmas—super hot, charged gases—and to developing practical solutions for creating fusion energy. The laboratory is managed by the university for the US Department of Energy’s Office of Science and is the largest supporter of basic research in the physical sciences in the United States and works to address some of the most pressing challenges of our time. For more information visit https://energy.gov/science