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Gamma-ray bursts (GRBs) are the brightest and most energetic explosions of light in the universe. Released by a huge cosmic explosion, a single GRB is capable of shining about a million billion times brighter than Earth’s sun, according to Nasa – and, for the most part, scientists can’t explain why they happen.
Part of the problem is that all known GRBs have come from far, far away – usually billions of Light years From the earth. Sometimes a GRB’s home galaxy is so far away that the bursting light seems to come out of nowhere, bursting briefly from the dark, empty sky and disappearing seconds later. These “empty skies” gamma ray bursts, as some astronomers call them, have been a permanent cosmic mystery for over 60 years. But now a new study, published on September 15 in the journal Nature, offers a compelling mathematical explanation of the origins of powerful bursts.
Related: The 12 strangest objects in the universe
According to the study’s researchers – who modeled the interactions between gamma rays and other powerful energy sources, such as cosmic rays – all of these nebulous bursts in the empty sky could be the result of massive star explosions. in the disks of distant galaxies.
“We modeled the emission of gamma rays from all the galaxies in the universe … and found that it is the star-forming galaxies that produce the majority of [empty-sky] gamma rays “, lead author Matt Roth, astrophysicist at the Australian National University in Canberra, said in a press release.
Explosions of the past
Astronomers favor two main explanations for the mystery of the gamma rays of the empty sky. In one explanation, the rays occur when gas falls into the supermassive black holes which are at the center of all galaxies in the universe. In this scenario, when the gas particles are sucked into the black hole, a small fraction escapes and radiates instead in large jets of matter close to the speed of light. It is believed that these powerful jets could be responsible for the gamma-ray bursts.
The other explanation points to stellar explosions called supernova. When large stars run out of fuel and burst into these violent supernovas, they can send nearby particles to explode at a speed close to light. These highly energetic particles, called cosmic rays, can then collide with other particles sprinkled in the gaseous hinterland between the stars, producing gamma rays.
In their new study, the researchers focused on this second explanation by modeling the interactions between cosmic rays and interstellar gas in various types of star galaxies. They found that the rate of gamma ray emission was influenced by several key factors, including the size of the galaxy, the rate of star formation (which affects the rate of supernovae), and the initial energy of the cosmic rays created. by every supernova.
Once the team had a model that predicted the rate of GRB for each galaxy size, they compared their model to an actual study of gamma radiation compiled by NASA’s Fermi Gamma Space Telescope. The researchers found that their calculations matched observations and that supernovas in star-forming galaxies could explain most, if not all, empty-sky GRBs.
“It is an important step to finally discover the origins of this gamma ray emission, solving a mystery of the universe that astronomers have been trying to decipher since the 1960s,” said Roth.
Black holes are probably still responsible for some of the gamma rays our satellites pick up, the researchers added. But when it comes to the mysterious empty-pit GRBs, the hungry holes just aren’t necessary; stars exploding in distant corners of the universe are enough to explain the phenomenon.
Originally posted on Live Science.
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