This week, astronomers released the first ever picture of a black hole. The picture of a supermassive black hole at the center of the M87 galaxy shows a bright disk of orbiting gas circling around a black hole and achieved an angular resolution of 20 micro-arcseconds. The center of the picture is the black hole’s shadow. The image was taken by the Event Horizon Telescope (EVT), which is a network of eight ground-based radio telescopes across the globe. The network includes the Atacama Large Millimeter Array (ALMA) located in Chile, the Atacama Pathfinder Experiment (APEX) also in Chile, the Institut de Radioastronomie Millimétrique (IRAM) in Spain, the James Clerk Maxwell Telescope (JCMT) and Submillimeter Array (SMA) in Hawaii, the Large Millimeter Telescope Alfonso Serrano (LMT) in Mexico, the South Pole Telescope, and the Arizona Radio Observatory in the United States of America.
The picture represents the culmination of decades of work to construct the EHT, which required collaboration and funding from institutions and agencies across the globe. Sheperd S. Doeleman, the project director, stated
“We have achieved something presumed to be impossible just a generation ago. Breakthroughs in technology, connections between the world’s best radio observatories, and innovative algorithms all came together to open an entirely new window on black holes and the event horizon.”
Computer modeling using a limited form of artificial intelligence has confirmed the existence of a new phase-state of matter. This new phase, chain-melting, exhibits the properties of both a solid and a liquid. For now, this new phase has only been confirmed for potassium atoms that are compressed under immense pressure. The experiment, published in the Proceedings of the National Academy of Science, showed that potassium atoms under extreme pressure could arrange into an elaborate structure of sub-lattices. The study authors used a neural network to model the interactions of several thousand potassium atoms under 20,000-40,000 times the atmospheric pressure of Earth. Under these conditions, the atoms would enter a phase called a chain-melted state. This new phase joins the other exotic states of matter that include plasma, bose-einstein condensates, superconductors, superfluids, degenerate matter, and quark-gluon plasma.
DeSalvo and colleagues used a mixture of bosonic caesium-133 atoms and fermionic lithium-6 atoms — bosons have integer spin angular momentum, whereas fermions have half-integer spin. The atoms were confined near the minimum of a harmonic trap, which is a type of potential-energy surface (often simply called a potential) that has a parabolic form. The authors cooled the mixture to extremely low temperatures, so that the caesium atoms formed an exotic state of matter known as a Bose–Einstein condensate (BEC), whereas the lithium atoms instead formed a quantum gas called a Fermi gas.
st experimental results demonstrating sustained, quasi-steady-state neutron production from the fusion Z-pinch experiment, operated with a mixture of 20% deuterium/80% hydrogen by pressure. While the Z-pinch is not a new plasma confinement concept, it was largely abandoned as a path for fusion energy because the plasma was not stable, which limited how long it could be confined. To get around this issue, we exploited the fact that flows can stabilize plasma, and our flowing plasma was maintained five thousand times longer than a static plasma. We also observed the sustained release of telltale energetic neutrons signaling nuclear fusion. Because this approach provides a path to nuclear fusion without coils, it could be used in the future for long-duration fusion burns in a compact and low-cost device.
“Magnetic field coils drive fusion devices to larger size and larger costs,” he says. “The coils are also particularly sensitive to neutron damage, which requires more shielding, further driving size and costs.”
A more efficient way to achieve these streams of plasma may be what is known as a Z-pinch confinement system. Rather than intricate webs of expensive magnetic coils, these systems pin the plasma in place with an electromagnetic field generated within the plasma itself. Z-pinch systems have been referred to as the dark horse of the nuclear fusion race, as the upside is a far simpler plasma configuration. The downside, however, is that instabilities cause distortions in the plasma that quickly cause it to hit the walls of the container vessel and collapse.
“Compressing and confining a plasma with magnetic fields in a Z-pinch configuration is prone to instabilities since the plasma can escape between the parallel magnetic field lines,” Shumlak tells us. “The magnetic field forms circular loops around the plasma column which confines the plasma radially, but the plasma can form bulges, like an aneurysm, which locally weakens the magnetic field and allows the bulge to grow.”
These problems have plagued the Z-pinch approach since its inception in the 1950s and effectively drove the development of tokamaks and stellarators, but the UW researchers say it still has something to give.
The reason for this, is that they believe they have figured out a way to stop the distortions that occur in the plasma and cause it to collapse. Through making slight adjustments to the behavior of the plasma by inducing what is known in fluid dynamics as sheared axial flow, the researchers were able to break new ground in their 50-cm-long (20-in) Z-pinch plasma column.
“The primary innovation is using plasma flows, specifically sheared axial flows,” Shumlak tells us. “The sheared flow stabilizes the plasma by constantly smoothing the plasma surface and preventing the bulges from developing.”
While the potential of sheared axial flow in Z-pinch plasma streams has been explored or years, the researchers write that this is the first time that they have produced “evidence of fusion neutron generation from a sheared-flow stabilized Z-pinch.” More specifically, their flowing plasma was held in place 5,000 times longer than a static plasma, and they were able to observe energetic neutrons that are the telltale signs of nuclear fusion.
While enthused by the breakthrough, given the unstable history of Z-pinch confinement systems and uncertainty of nuclear fusion research as a whole, they are taking a cautiously optimistic outlook.
“As a scientist, I would state that we do not know for certain if this advance will lead to a new dawn,” says Shumlak. “However, the results are particularly encouraging. Sheared flow stabilization of the Z-pinch approach has been thoroughly investigated, and the predictions of scaling to current performance have been demonstrated. The evidence is described in our Physical Review Letters article. If our current scientific understanding continues to hold, then we should be able to reach even higher performance.”
This week, NASA announced that they had allocated funding for 18 new projects under their Innovative Advanced Concepts Program. The projects include space to ground power beaming, a self-healing spacesuit, electro-static microprobes, space debris collection, polar ice mining, light sails, beamed propulsion, and neutrino detection. The NASA Innovative Advanced Concepts (NIAC) Program is designed to nurture visionary ideas that could transform future NASA missions with the creation of breakthroughs that are radically better or entirely new aerospace concepts Jim Reuter, the acting associate administrator of NASA’s Space Technology Mission Directorate stated that “Our NIAC program nurtures visionary ideas that could transform future NASA missions by investing in revolutionary technologies. We look to America’s innovators to help us push the boundaries of space exploration with new technology.”