First discovered by accident by military satellites whose main mission was to detect space-based nuclear explosions, gamma ray bursts are highly energetic explosions that astronomers have yet to fully understand. Collisions between black holes or neutron stars have the potential to release such massive amounts of energy, but it isn't known if this is the cause of the bursts.

They were first observed in the mid-1960s but were not reported in scientific journals until 1973. Because Earth's atmosphere filters out gamma radiation (thank goodness!) bursts can only be observed from space. NASA launched the Compton Gamma Ray Observatory in 1991 to study bursts among other phenomenon, but this satellite was purposefully de-orbited in June 2000.

Bursts occur on average once a day. They occur randomly in all directions. Often the bursts outshine all other gamma ray sources in the sky then fade away leaving no trace. Bursts are accompanied by energy in other wavelengths, but because the bursts are so fleeting and often extremely distant, observing bursts at other wavelengths is quite a challenge, especially at when they are at their brief peak intensity.

In 1998 astronomers detected a burst which turned out to be the most energetic event in the Universe since the Big Bang. Occuring 12 billion light years away (only a couple billion years younger than the Universe itself), the explosion was several hundred times bigger than a typical supernova, which was the old benchmark for big explosions.

They remain one of the great unexplained questions in modern science.

A gamma ray burst, as the name suggests, is a huge amount of gamma radiation released in space, that contains roughly the same amount of energy as a supernova. Unlike supernovae however, the energy in a gamma ray burst is released in a matter of seconds (between 30ms-1000s) as opposed to days, weeks or even months as the case may be with the former.

They are detected with two types of telescope, one to closely examine an area of the sky, not unlike a wide angle lens on a camera, and another to focus the x-rays onto a sensor. The sensor is hooked up a computer equipped with sophisticated artificial intelligence software that can pick out the extragalactic bursts of energy faster than any human could by hand.

When looked at in terms of matter and energy, imagine that the amount of material it takes to create a 1 megaton nuclear explosion could fit into a coffee jar. Now imagine the size of the explosion if instead of a coffee jar's worth of material, you had an entire star's worth. Now you're in the ball park.

Gamma ray bursts were first discovered by satellite detectors in the sixties. When these strange busts of radiation were discovered, government scientists thought that the Soviet military were conducting clandestine nuclear tests, or that the bursts might be emissions from some alien spacecraft. It was only later when it was discovered that the bursts originated deep in outer space that the information was declassified and made available to the public.

The bursts are not limited to one particular part of outer space, but occur randomly and without pattern. The one thing they do have in common is that nobody knows for sure what causes them.

The effect of a gamma ray burst (GRB) in the vicinity of Earth (say 3,000 light years or so) could be disastrous, even worse than a giant meteor impact. About once every hundred million years such an explosion occurs in our galaxy.

Our ozone layer (which protects us against UV radiation) would be completely destroyed and the atmosphere would be polluted with toxic radioactive particles, produced by the intense gamma radiation.

In fact, some scientists believe these bursts have sterilized huge parts of the universe (a possible reason why we haven't found extraterrestrial life yet).

  • A popular theory is the neutron star-merger (aka "relativistic fireball") : a neutron star merges with another neutron star or a black hole. As a result, it releases the very energy-intense radiation.
  • A newer theory assumes they're produced by hypernovae (huge shortlived stars collapsing into black holes).

There's evidence the bursts occur in regions where new stars are formed and could be a part of this process of birth.
Maybe the process that created the conditions for life on Earth will also be responsible for its destruction...


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