An international team of physicists has created the first small-scale replica of gamma ray bursts in a laboratory, opening up a whole new way to investigate the properties of these mysterious flashes of intense high-energy radiation that appear from random directions in space. The results are published in the journal Physical Review Letters (arXiv.org preprint).
This artist’s impression shows a gamma-ray burst in a star forming region. Image credit: L. Calçada / ESO.
Gamma ray bursts are among some of the brightest events that have ever been observed in the Universe.
However, because they occur in short bursts and originate in distant galaxies, astrophysicists have not been able to exactly pinpoint what causes them.
Some might even suggest they may be messages from advanced alien civilizations but many experts have predicted that the bursts are emitted when jets of particles are thrown out by massive astrophysical objects, such as black holes.
For this theory to work, the beams released by black holes would have to have strong, self-generated magnetic fields and the rotation of particles around the fields would then give off powerful bursts of gamma ray radiation.
Dr. Gianluca Sarri of Queen’s University Belfast and colleagues have now been able to prove for the first time, some of the key phenomena that play a major role in producing gamma ray bursts.
This illustration shows the ingredients of the most common type of gamma-ray burst. The core of a massive star (left) has collapsed, forming a black hole that sends a jet moving through the collapsing star and out into space at near the speed of light. Radiation across the spectrum arises from hot ionized gas in the vicinity of the newborn black hole, collisions among shells of fast-moving gas within the jet, and from the leading edge of the jet as it sweeps up and interacts with its surroundings. Image credit: NASA’s Goddard Space Flight Center.
The team made use of the Astra-Gemini laser, hosted by the Central Laser Facility at the Rutherford Appleton Laboratory, UK, to create the mini gamma ray burst.
“We thought that the best way to work out how gamma ray bursts are produced would be to mimic them in small-scale reproductions in the laboratory — reproducing a little source of these beams and look at how they evolve when left on their own,” Dr. Sarri said.
“During the experiment, we were able to confirm that the current models used to understand gamma ray bursts are on the right track, predicting the right mechanisms for the magnetic field generation and gamma-ray emission.”
“The experiment is also useful as the beams are entirely made up of electrons and positrons, which is a peculiar state of matter. In an electron-positron beam, both particles have exactly the same mass, leading to fascinating consequences. For example, sound would not exist in an electron-positron world.”
“The research could also unlock some major clues in the search for alien life,” he added.
The Search for Extra-Terrestrial Intelligence (SETI) investigation looks for messages in space that cannot be explained naturally and that could potentially be originating from an alien civilization.
“If you really want to search the Universe for alien transmissions, you first need to make sure all the natural emissions are understood so that they can be ruled out,” Dr. Sarri said.
“Our study helps towards understanding black hole and pulsar emissions, so that, whenever we detect anything, we can determine straight away if it can be explained naturally or if it has come from an alien civilization.”
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J. Warwick et al. 2017. Experimental Observation of a Current-Driven Instability in a Neutral Electron-Positron Beam. Phys. Rev. Lett 119 (18): 185002; doi: 10.1103/PhysRevLett.119.185002
