A confirmation of the theory of general relativity from the most powerful gamma-ray burst ever detected

Artist's concept of gamma-ray burst (Image courtesy Superbossa.com e Alice Donini)
Artist’s concept of gamma-ray burst (Image courtesy Superbossa.com e Alice Donini)

An article published in the journal “Physical Review Letters” reports a measurement of the invariance of the speed of light in vacuum at different energies thanks to observations of the gamma-ray burst cataloged as GRB 190114C, the most powerful ever observed. The scientists from the MAGIC Collaboration used the data collected by the two MAGIC telescopes in the Canaries to investigate in particular a phenomenon called Lorentz invariance violation (LIV), ending up with yet another confirmation of Albert Einstein’s theory of general relativity.

On January 14, 2019, various telescopes participated in the multiband observation, which means at frequencies of different bands of the electromagnetic spectrum, of the GRB 190114C gamma-ray burst. This event was truly extraordinary even by the standards of these extremely energetic events because it was the first observed at TeraelettronVolt (TeV) energies. Gamma-ray instruments detected these extremely energetic emissions at various levels but other emissions filled the spectrum and were detected down to radio waves.

Among the ground instruments that participated in the observations of the GRB 190114C gamma-ray burst, there are the MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescopes, capable of detecting gamma rays at such high energies. For this reason, they were crucial in the study of this event, and now this new research also contributes to a verification of the invariance of the speed of light in vacuum at different energies. One of the problems of today’s physics is the difficulty of combining the theory of relativity and quantum theory. For example, according to some theories, at an extremely small scale, space-time is a thin lattice and not a continuous surface. The consequence is that, especially at higher frequencies, there may be interference in the speed of light in vacuum.

Gamma-ray bursts are ideal for studying these theories because their emissions come from a few billion light-years away, are extremely energetic and at various frequencies. The MAGIC Collaboration researchers analyzed the data recorded on the occasion of the GRB 190114C event. The result is that there was no energy-dependent delay in the arrival times of gamma rays, which is what would have happened if there was a quantization of space-time in accordance with the tested theories.

In essence, this places very strict limits on quantum gravity, a confirmation of results deriving from previous analysis of gamma-ray bursts. It’s an important confirmation because the distance and above all the extremely-high-energy of the GRB 190114C event offer greater precision in the test. It’s also yet another confirmation of the theory of general relativity. In the future, other gamma-ray bursts may be examined that way with MAGIC or other specialized instruments.

The afterglow of GRB 190114C observed by Hubble (Image NASA, ESA, and V. Acciari et al. 2019)
The afterglow of GRB 190114C observed by Hubble (Image NASA, ESA, and V. Acciari et al. 2019)

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