Gamma Ray Bursts.

The Ultimate Explosion.

Described as the most destructive force in the Universe, Gamma Ray Bursts are only a recent discovery.


However it quickly became apparent that GRB’s carry with them the power to vaporise everything within hundreds of light years.

     

Extraordinary explosions.

Imagine an explosion so fierce and intense that it carries with it the power to destroy everything in its path for hundreds if not thousands of light years away. No this isn’t the realms of science fiction but the amazing world of Gamma Ray Bursts.

Astonishing discovery.

Gamma Ray Bursts, or GRBs as they are otherwise known were first detected during the late 1960’s. US monitoring equipment on a space satellite set up to detect Soviet nuclear weapons testing began to notice intense gamma ray bursts that were hard to explain.

For a long time it also proved impossible to determine the origin of these bursts. Then in the last decade of the 20th century astronomers made the astonishing discovery that these phenomenal bursts of radiation emanated from the observable extremities of the known Universe.

Nothing rare.

Dramatic though the discovery of Gamma Ray bursts was, there is nothing particularly rare about them since they were, and continue to be spotted at a rate of around one a day. But what were these bursts? They were obviously some form of intense radiation coming from an unimaginably distant location but how could they be explained?

Very quickly astronomers began to surmise that GRBs were exploding stars. These are usually known as supernovas but GRBs were in a whole new category and made even the tremendous force of a supernova look minuscule by comparison. Scientists have now speculated that Gamma Ray Bursts may be associated with black holes capable of releasing a fireball of energy into a high pressure jet that in turn creates the shock waves that lead to the formation of Gamma Rays.

Long and short duration.

For all their astonishing power GRBs are of extremely short duration and fall into two categories. The first involves those with an average of just a third of a second and others with a much longer average span of 30 seconds. Astronomers then conjectured that different causal forces lay behind the origin of the two categories. As it is there is still a huge amount we do not understand about GRB’s, but one thing we do know for sure is the great damage they would be capable of causing.




Captured images of a Gamma Ray Burst.

Deadly consequences.

Since most GRBs are at the extremities of the Universe and occurred when the Earth was very young there is seemingly nothing to worry about. Yet the very nature of GRBs mean that an explosion at even several thousand light years distance could prove deadly to all life on Earth. Indeed some scientists believe that GRBs were responsible for at least some of the frequent mass extinction’s that have swept the planet over millions of years. For more on the possibly drastic implications that GRB’s could hold for our planet please turn to the accompanying link:

http://www.nature.com/nsu/030922/030922-7.html

Our Sun – the ultimate end!

For the ultimate disaster representing the End of the Worldwe should look no further than our own Sun. Eventually – in many millions of years – this too will erupt in a vast fireball and completely vaporise our planet. This may be a long time in the future but the Sun has shown recent signs of an increase in activity.

For more on this please turn to our special topic.

The Sun is getting stronger.

 

Gamma-ray burst linked to mass extinction

440-million-year-old fossils hint at cosmic explosion.

Philip Ball

Over 100 families of marine invertebrates, including trilobites, died out at the end of the Ordovician period.

Over 100 families of marine invertebrates, including trilobites, died out at the end of the Ordovician period.© GettyImages

Some 440 million years ago, a nearby gamma-ray burst may have extinguished much of life on Earth, say US astronomers1.

Adrian Melott, of the University of Kansas in Lawrence, and colleagues reckon that the fossil record of the end of the Ordovician period fits with how such a cosmic explosion a few thousand light years away could have altered the environment. At that time, more than 100 families of marine invertebrates died out; it was the second most devastating mass extinction in our planet’s history.

The possibility of life on Earth being affected by cosmic events has been long recognized. Giant asteroid impacts have been proposed as a cause of global wildfires and climate cooling that could have been behind events such as the extinction of the dinosaurs 65 million years ago.

Researchers have also suggested that supernovae – explosions of old stars – could flood our planet with deadly radiation if they happen within around 100 light years of us (our galaxy is 150,000 light years across). This has been put forward as the cause of the mass extinction two million years ago.

Compared to gamma-ray bursts (GRBs), supernovae are just firecrackers. Most GRBs come from beyond our galaxy. They are visible across such immense distances because they are extraordinarily bright and powerful, despite lasting just seconds.

It seems increasingly likely that they are linked to supernovae. Jets or blobs of material thrown out from a collapsing star could produce a flash of gamma rays when they collide with the gas between stars.

Flash in the past

Water would protect marine organisms from the heat of a GRB, but not from its other effects, argues Melott’s team. Its gamma-rays would convert some nitrogen and oxygen in the atmosphere into nitrogen dioxide, the brownish gas present in urban smog.

Nitrogen dioxide would filter out sunlight, turning the skies dark. The cooling effect could trigger an ice age – there is evidence of widespread glaciation 440 million years ago. Nitrogen oxides also cause acid rain and destroy the ozone layer, exposing Earth to more of the Sun’s harmful ultraviolet rays.

Ultraviolet radiation can penetrate tens of metres of water, so it could harm marine organisms at these depths. Indeed shallow-dwelling species, or those that spend their early lives in shallow water, seem to have suffered more than deep species in the Ordovician extinction.

In short, a nearby GRB might first have showered harmful radiation onto the exposed face of the planet, killing more or less indiscriminately, and may then have exposed the other hemisphere to increased ultraviolet radiation, damaging marine life decreasingly with increasing depth.

The fingerprint of such an event might be revealed by gathering more information about the geographical pattern of the Ordovician extinctions, the researchers conclude.

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