(ORDO NEWS) — Gamma-ray bursts are the strongest and brightest explosions in the universe and are thought to be generated during the formation of black holes.
Although gamma-ray bursts last only a few seconds, they produce as much energy as the sun emits during its entire 10 billion years of existence.
The mysterious phenomena were first discovered in 1967 by a US Air Force satellite called Vela. According to NASA, the probe was designed to monitor secret Soviet nuclear tests, but it ended up detecting blinding gamma rays – the most powerful electromagnetic radiation coming from outside the solar system.
When such an event occurred, it briefly became the brightest gamma-ray object in the observable universe.
It wasn’t until 1991 that astronomers launched the Compton Gamma Observatory, which recorded roughly one new gamma-ray burst per day.
The BATSE instrument found that the GRBs were distributed evenly across the sky, meaning they occur everywhere in space. BATSE also showed that there were two types of GRBs with different signatures: those that lasted between 2 and 30 seconds, and those that flickered for less than 2 seconds.
Since then, researchers have learned a lot more about gamma-ray bursts by developing a network of rapid response satellites and ground-based observatories that all target a gamma-ray burst as soon as it is detected.
This network has provided data showing that gamma-ray bursts are located in galaxies billions of light-years away, and that after the initial gamma-ray flare, the source of the flare produces an afterglow at less energetic wavelengths.
Where do gamma-ray bursts come from?
Longer-lived versions of gamma-ray bursts have been found to be associated with super-powerful supernovae called hypernovae, which occur when stars five to 10 times the mass of our Sun end their lives and become black holes.
Hypernovae are 100 times brighter than typical supernovae and are thought to form from stars that spin especially fast or have a particularly strong magnetic field that adds extra energy.
But short-term gamma-ray bursts, which make up 30% of such events, remained a mystery until 2005, mainly because they are too fast and fleeting for subsequent observations.
After NASA launched the SWIFT observatory in 2004, it was finally able to record enough data to see the afterglow of short-lived gamma-ray bursts and figure out that they were likely sent from two superdense neutron stars that collided and formed a black hole, or when a black hole ate a neutron star. star.
Such flashes are so strong that they create ripples in the fabric of space-time called gravitational waves. Now that researchers have launched the Laser Interferometric Gravitational Wave Observatory (LIGO), which can detect gravitational waves from these collisions, we can gather even more information about the processes that underlie short-lived gamma-ray bursts.
There are still many unknowns about gamma-ray bursts. Recent observations have shown that all photons emitted by gamma-ray bursts oscillate in the same direction, but for some reason the direction changes over time.
“What it could be, we really don’t know,” said Merlin Cole, a scientist at the University of Geneva in Switzerland and one of the study’s leaders, after the 2019 discovery.
Gamma-ray bursts also seem to focus their energy in a narrow beam rather than radiating it equally in all directions, which means our satellites miss a lot of them.
Astronomers estimate that although satellites detect about one gamma-ray burst per day, there are about 500 of them per day.
So far, gamma-ray bursts have only been detected in distant galaxies. However, it is possible that this will happen in our galaxy – the Milky Way.
The Ordovician extinction – one of the five major extinction events in our planet’s history – occurred about 450 million years ago and may have been caused by a gamma-ray burst ice age.
If a new gamma-ray burst were to occur near Earth, it would strip us of our protective ozone layer and expose all life to deadly ultraviolet radiation. Thus, scientists agree that they do not observe bursts in our home galaxy.
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