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E=mc^2... right?!

On October 9th 2022, few may have noticed their radios crackling a bit. The robots watching the sky noticed something, though. And then they started sending out alerts.

What they "saw" was the result of a stellar explosion two billion light years away and two billion years in the past finally making its way to us. Except this was not like the previous ~1,700 gamma ray bursts previously detected. This was at least an order of magnitude more energetic, indicating that for the first time (since humanity has been watching), one of the collimated jets that burst forth from the poles of the dying star was pointed directly at Earth.

This is the holy grail of gamma ray burst research. Wen-fai Fong, an astrophysicist at Northwestern University, even went so far to call it a once-in-a-lifetime event:

“I kept thinking, is this real? Because if it is, it’s an extremely rare, once-in-a-lifetime type of event”

A directed jet alone is not what is fascinating about this event though, as that was just random chance. An extremely rare chance sure, but random chance nonetheless.

It’s this little guy that is causing so much excitment:

Among those detections was a suspected high-energy photon at 18 teraelectron volts (TeV)—four times higher than anything seen from a gamma-ray burst before and more energetic than the highest energies achievable by the Large Hadron Collider.

A spurious photon detected with such high energy that our current physical understanding tells us it should not have been able to travel the 2 billion light years to us without shedding a significant portion of that energy as it transited through and interacted with the interstellar medium and background radiation.

One current theory postulates it was transformed in-transit into an "axion", an incredibly lightweight particle not unlike a neutrino in that it can travel great distances without interacting with anything else:

One possibility is that, following the gamma-ray burst, a high-energy photon was converted into an axion-like particle. Axions are hypothesized lightweight particles that may explain dark matter; axion-like particles are thought to be slightly heftier. High-energy photons could be converted into such particles by strong magnetic fields, such as the ones around an imploding star. The axion-like particle would then travel across the vastness of space unimpeded. As it arrived at our galaxy, magnetic fields would convert it back into a photon, which would then make its way to Earth.

The magnetic field of Earth would have transitioned this particle back into a high-energy photon for detection. If this theory holds, it would provide the first direct & concrete proof of the existence of dark matter. As important as this would be it would not require new or altered physics, but rather a confirmation of the physics we’ve developed to this point.

However... another suggests that instead the speed of light itself is not constant as we’ve always understood it to be, but rather is dynamic when reaching into the high-energy realm. Such a discovery may require fundamental alterations of the theory of relativity itself, asking humanity to adjust its base understanding of the universe accordingly:

It is postulated in Einstein’s relativity that the speed of light in vacuum is a constant for all observers. However, the effect of quantum gravity could bring an energy dependence of light speed, and a series of studies on high-energy photon events from gamma-ray bursts (GRBs) and active galactic nuclei (AGNs) suggest a light speed variation v(E) = c (1 − E/ELV) with ELV = 3.6 × 1017 GeV. From the newly observed gamma-ray burst GRB 221009A, we find that a 99.3 GeV photon detected by Fermi-LAT is coincident with the sharp spike in the light curves detected by both Fermi-GBM and HEBS under the above scenario of light speed variation, suggesting that this high energy photon was emitted at the same time as a sharp spike of low energy photon emission at the GRB source. Thus this highest energy photon event detected by Fermi-LAT during the prompt emission of gamma ray bursts supports the linear form modification of light speed in cosmological space.
(emphasis added)

It is because of this possibility that this detection may be the single most consequential astrophysical detection of our lifetimes, overshadowing even the recent LIGO detections which — while monumental in their own right — were simply the final experimental confirmation of physics already theorized and believed to be understood.

What is known for certain now? Not much, frankly. It may take years to comb through the data & filter out noise, because as one researcher noted, the instruments normally used to detect these events are tuned to detect a small number of incoming particles:

“Our instruments are very sensitive, and they’re meant to detect faint sources,” says Judith Racusin, a deputy project scientist of the Fermi Space Telescope. But this time, millions of photons were collected. “They all kind of get jumbled together,” she says. “So instead of detecting the energy of each individual gamma ray, we detect the sum of the energy of those gamma rays.” That’ll make it hard to extract information from the true number of photons observed and their energies—one downside to the blast being so extraordinarily bright.

This event was so energetic and voluminous that it overwhelmed these sensors: imagine having your camera setup for the dark and then pointing it at a bright point source.

So the world waits. Here’s to all the scientists around the world currently frantically trying to make sense of GRB 221009A. Not to put too much of a point on it, but humanity is depending on you!

References & futher reading: