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A photon from the biggest cosmic explosion since the Big Bang appears to have defied Einstein. Scientists may finally know how
"We started from a very simple question: how did this photon survive a journey that, according to known physics, should have destroyed it?"
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A photon, or particle of light, from the biggest cosmic explosion since the Big Bang, nicknamed "the BOAT" (for the brightest of all time), should not have reached Earth. That is, unless it defied rules defined by Einstein. Now scientists may know how it did this, with new research suggesting how the high-energy photon may have survived a journey of more than two billion light-years without being absorbed.
The BOAT, a gamma-ray burst officially designated GRB 221009A, was first detected on Oct. 9, 2022. Among the ocean of photons from the event that rained down on our planet was the highest-energy photon ever detected originating from a gamma-ray burst. It was detected by Carpet, an ultra-high-energy cosmic-ray detector located at the Baksan Observatory in the Russian Caucasus.
The problem is, according to all current rules of physics, a particle with such high energy shouldn't reach Earth from an explosion occurring such a vast distance away. That's because space isn't empty; it is filled with a "fossil" radiation field of photons left over from just after the Big Bang called the cosmic microwave background (CMB). It should be virtually impossible for a high-energy photon to travel 2 billion light-years without interacting with a CMB photon and being transformed. And still it came.
"We started from a very simple question: how did this photon survive a journey that, according to known physics, should have destroyed it?" team leader Giorgio Galanti from the Italian National Institute for Astrophysics (INAF) said in a statement. "The new data from the Carpet experiment showed us that the explanations proposed so far were no longer sufficient. "We therefore looked for a theoretical scenario capable of consistently describing what we observe, without resorting to arbitrary corrections to the equations."
To investigate the mystery of how this high-energy photon reached our planet, Galanti and colleagues turned to incredibly light hypothetical particles called axion-like particles (ALPs).
ALPS could serve as a solution to this puzzle via a mechanism that would allow photons to transform into ALPs as they travel and then convert back into photons as they reach the Milky Way. The problem is that this still can't account for such a high-energy photon.
This team combined the idea of ALPs with a proposed violation of one of the fundamentals of Einstein's 1905 theory of special relativity called "Lorentz invariance."In short, Lorentz invariance says that observers moving at different speeds should experience the same physical laws. The team tested the idea that Lorentz invariance could be violated at high energies, thus changing how photons propagate through space.
In the scenario devised by the team the photon would have avoided being wiped out by interactions with the CMB as it would avoid interactionc with these fossil photons.