A very powerful explosion directed towards Earth has signaled the complete annihilation of a star.
Every now and then, the night sky lights up with a spectacular explosion that sparkles with the most energetic light our Universe can produce so bright and powerful that we can't see it. Known as gamma ray bursts,. or Gamma Ray Burnst, can release in a few seconds what our Sun emits over its lifetime.
Now scientists have found a never-before-seen signal, buried in the spectrum of electromagnetic radiation emitted by the brightest gamma-ray burst ever recorded.
This signal is an emission light: a bright region in the gamma-ray spectrum produced by something emitting light in that specific wavelength range. And this something, scientists have determined, is complete and utter destruction: the mutual annihilation of electron-positron pairs, matter and its antimatter counterpart.
Nicknamed “the BOAT” (an acronym for Brightest Of All Time), the burst was detected in October 2022. It was the result of the explosion of a huge star whose core collapsed into a black hole, releasing so many energetic photons that it was difficult to make accurate measurements. The related research was published in Science .
But the measurements were made, and scientists quickly realized they were observing something special.
The BOAT as recorded by NASA
“A few minutes after the BOAT explosion, Fermi's Gamma-ray Burst Monitor recorded an unusual energy spike that caught our attention,” says astrophysicist Maria Edvige Ravasio of Radboud University in the Netherlands.
“When I first saw that sign, I got goosebumps. Our analysis has since shown that this is the first high-reliability emission line seen in 50 years of studying gamma-ray bursts."
Emission lines on the spectrum, as an example (Beryllium) NASA
Emission lines, which appear as bright bars on the spectrum of light emitted from a source, indicate that something is causing light of particular wavelengths to shine brighter – a source of extra emission. Likewise, darker bars, known as absorption lines, can appear where wavelengths of light are absorbed.
Emission and absorption characteristics can tell us a lot about the constitutive chemistry of various astrophysical processes, from the metallicity of stars to the molecules that make up the atmospheres of distant planets.
There are several scenarios that can produce a gamma-ray burst, an explosion of the most energetic light in the electromagnetic spectrum, but what the BOAT – officially named GRB 221009A – produced was the birth of a black hole. The star's outer material was violently ejected into space, while the core collapsed under gravity, forming the densest type of object in the Universe.
This explosion was accompanied by jets or particles exploding in certain directions. This is what we see in a gamma-ray burst, with the jet angled towards our line of sight.
When GRB 221009A first exploded, the brightness was so extreme that it obscured any detail. In 80 seconds, the burst went from a peak energy of 12 million electron volts to about 6 million electron volts. Just five minutes later, the brightness dimmed enough for the Fermi telescope to distinguish an emission line that lasted at least 40 seconds.
Researchers believe a phenomenon called annihilation is responsible for the increased glow. When an electron and its antimatter counterpart, a positron, collide, they produce a photon with an energy of 0.511 million electron volts. So the energy released was such that it created antimatter which, in turn, annihilated itself by generating gamma rays.
The emission characteristic observed in BOAT reflects a much higher energy, but researchers have an explanation for this. The annihilation occurred in a jet moving towards us at about 99.9% of the speed of light. This made the energy appear much higher than it was, an illusion based on our viewing angle that can be seen in other astrophysical jets.
“Because we are looking inside the jet, where matter is moving at close to the speed of light, this emission becomes very blueshifted and pushed towards much higher energies,” explains astrophysicist Gor Oganesyan from Gran Sasso Science Institute in Italy .
Although it appeared that GRB 221009A was an extreme example of a gamma ray burst, subsequent observations and analyzes later revealed that the BOAT was in fact completely normal: its brightness was only the result of its orientation, because the gamma rays were exactly headed in the direction of the Solar System.
Double good news: we were not "cooked" by the Gamma burst and, furthermore, we had the vision of a ray directly directed towards the Earth, with a privileged viewing point.
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The article A very powerful explosion directed towards Earth has signaled the complete annihilation of a star. comes from Economic Scenarios .
This is a machine translation of a post published on Scenari Economici at the URL https://scenarieconomici.it/una-potentissima-esplosione-diretta-verso-la-terra-ha-segnalato-la-completa-annichilazione-di-una-stella/ on Sat, 03 Aug 2024 19:43:09 +0000.