How Do Gamma-Ray Bursts Happen?

 

The largest and brightest explosions in the cosmos, known as gamma-ray bursts, are considered to be produced during the creation of black holes. Gamma-ray bursts create as much energy in their brief lifetimes as the sun will in its whole 10-billion-year lifespan. 

The unexplained phenomenon was originally seen in 1967 by the Vela satellite of the U.S. Air Force. According to NASA, the probe discovered brilliant gamma-rays, the most potent electromagnetic radiation, emanating from beyond the solar system while monitoring covert Soviet nuclear tests. When such an occurrence had a place, it would momentarily become the universe's brightest gamma-ray object.

The Burst and Transient Source Experiment (BATSE), which identified about one new gamma-ray burst every day, was not initiated by astronomers until 1991, when the Compton Gamma Ray Observatory was. According to the Australian Swinburne University of Technology, BATSE discovered that gamma-ray bursts were uniformly scattered across the sky, indicating that they were happening everywhere in the cosmos. Gamma-ray bursts that lasted between two and thirty seconds and those that flashed for less than two seconds both had different characteristics, according to BATSE.

Since then, by creating a network of quick-response satellites and ground-based observatories that all focus on a gamma-ray burst as soon as it is identified, researchers have learnt a great deal more about gamma-ray bursts. This network's data demonstrate that gamma-ray bursts occur in galaxies billions of light-years away and that the source of the burst emits an afterglow at less energetic wavelengths after the original gamma-ray flare.

 

Where do gamma-ray bursts come from? 

According to NASA, the ultrapowerful supernovas known as hypernovas, which happen when stars that are five to ten times as massive as our sun die and collapse into black holes, are linked to the longer-lasting varieties of gamma-ray bursts. Hypernovas are theorised to be produced by stars that spin very quickly or have unusually strong magnetic fields, adding more energy to their combustions and making them 100 times brighter than conventional supernovas.

However, the 30% of such events that are short-lived gamma-ray bursts remained a mystery until 2005, mostly because they are too rapid and transitory for follow-up studies. After being launched in 2004, NASA's Neil Gehrels Swift Observatory (previously known as the Swift Gamma-Ray Burst Explorer) was finally able to gather enough data to observe the afterglow of brief gamma-ray bursts and determine that they were probably brought on by the collision of two ultradense stellar corpses known as neutron stars and the formation of a black hole, or when a black hole ate a neutron star. 

These explosions are so powerful that gravitational waves, which are ripples in space-time, are created. Researchers anticipate being able to learn significantly more about the mechanisms driving short-lived gamma-ray bursts now that the Laser Interferometer gravity-Wave Observatory (LIGO), which can detect gravity waves from these collisions, has been turned on. 

 The mystery is still at every turn...

Gamma-ray bursts remain the subject of many unanswered questions. The photons released during gamma-ray bursts oscillate in the same direction, according to recent findings, but for some reason, the direction changes with time. After this 2019 finding, Merlin Kole, a scientist at the University of Geneva in Switzerland and one of the study's principal investigators, stated in a statement, "What this could be, we really don't know."

Additionally, gamma-ray bursts appear to concentrate their energy into a narrow beam as opposed to discharging it evenly in all directions, which is why our satellites are missing a large portion of them. Although satellites only record one gamma-ray burst each day, astronomers believe that 500 are active at any given moment. 

Gamma-ray bursts have only been found in far-off galaxies thus far. Nevertheless, one might happen in the Milky Way galaxy. One of the five major extinction catastrophes in the history of our planet, the Ordovician, occurred around 450 million years ago and may have been brought on by an ice age that was set off by a gamma-ray burst. The ozone layer that shields Earth from dangerous UV radiation would be removed if a fresh gamma-ray explosion occurred nearby. Therefore, even though it would be amazing to see a gamma-ray burst up close someday, scientists are okay with not seeing one in our galaxy.