Fast radio bursts are one of the greatest cosmic mysteries of our time. They are extremely powerful but extremely brief explosions of electromagnetic radiation in radio wavelengths, discharging in milliseconds as much energy as 500 million Suns.
Scientists have been puzzled about what was causing these brief outbursts, detected in galaxies millions to billions of light-years away. Finally, in April 2020, we got a really solid lead: a brief, powerful flash of radio waves from something inside the Milky Way a magnetar.
According to the QED, these extremely magnetized dead stars produce at least some speed radio bursts. Physicists have devised a technique to refute what they believe in the first stages of these insane explosions in a lab.
"Our laboratory simulation is a small-scale analog of a magnetar environment," said Princeton University professor Kenan Qu. "This allows us to analyse QED pair plasmas."
A magnetar is a form of a dead star called a neutron star. When a massive star reaches the end of its life, it blows off its outer material, and the core, no longer supported by the outward pressure of nuclear fusion, collapses under its own gravity to form an ultra-dense object with a powerful magnetic field. That''s the neutron star.
Several neutron stars have a more powerful magnetic field. That''s a magnetar. We don''t know how they get this way, but their magnetic fields are 1,000 times greater than they are in a regular neutron star, and this is a quadrillion times more powerful than Earth''s.
Scientists believe that rapid radio bursts are a result of the tension between the magnetic field, which is so strong it distorts the magnetar''s shape and the inner pressure of gravity.
The magnetic field is also thought to be responsible for moving the matter in space around the magnetar into a plasma composed of matter-antimatter pairs. These pairs consist of a negatively charged electron and positively charged positron, and they are believed to play a role in the emission of rare fast radio bursts that repeat.
This plasma is a pair plasma, and it is very different to most of the Universe''s plasma. Normal plasma consists of electrons and heavier ions. The matter-antimatter pairs in pair plasma have identical masses and spontaneously form and destroy each other. Pair plasmas'' collective behavior is very different from those of normal plasmas.
Because the potential of these magnetic fields is so severe, Qu and his colleagues devised a technique to create pair plasmas in a lab via other means.
"We don''t simulate a strong magnetic field, but we utilize a powerful laser," Qu adds.
"It converts energy into pair plasma through QED cascades. The pair plasma then shifts the laser pulse to a higher frequency. "The exciting conclusion demonstrates the possibility of creating and observing QED pair plasma in laboratories and enabling experiments to verify theories about fast radio bursts."
The technique involves generating a high-speed electron beam while traveling at close to the velocity of light. This beam is triggered by a moderately powerful laser, and the collision results in a pair plasma.
Moreover, the plasma produces a lot of damage, thus this may be solved in one of the previous experiments to create pair plasmas that are observing their collective behavior.
"We believe we know what laws govern their collective behavior," says a physicist at Princeton University. So until we actually produce a pair plasma that displays collective phenomena that we can investigate, we cannot be completely sure of that."
"The problem is that collective behavior in pair plasmas is quite difficult to perceive. "We should examine this as a combined production-observation problem, recognizing that a great method of observation relieves the quality of the production and leads us to a more practicable user facility."
The study is yet to be completed, but it provides a way to conduct these investigations that hasn''t been previously encountered. It reduces the need for extremely powerful equipment that may be beyond our technical capabilities and budgets.
The team is preparing to test their ideas in a series of experiments at the SLAC National Accelerator Laboratory. This will help them understand how magnetars can generate pair plasmas, how their pair plasmas might produce rapid radio bursts, and how to identify previously unknown physics.
"In a sense, what we are doing here is the beginning point of the cascade that produces radio bursts," says Stanford University physicist Sebastian Meuren.
"If we could see something like a radio burst in the lab that would be fantastic," he adds. The first part is to observe the scattering of electron beams, and once we do that, we''ll improve the laser intensity to produce high densities in order to actually see the electron-positron pairs. "Our experiment will evolve over the next two years or so."
It may take a while to get our answers on rapid radio bursts. However, if we''ve learned anything over the years, it''s that discovering this fascinating mystery is absolutely worth the wait.
The paper from the team has been published in Physics of Plasmas.