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article imageStudy suggests Gamma-ray burst may have hit Earth in 8th century

By Andrew Moran     Jan 21, 2013 in Science
London - A new study published in the Monthly Notices of the Royal Astronomical Society suggests that Earth may have been hit by a gamma-ray burst, the strongest explosion in the universe, in the eighth century.
Gamma ray bursts (GRBs) are luminous electromagnetic occurrences that are mostly known to transpire in distant galaxies during a supernova event or when a star collapses and forms a black hole. These blasts can take place from a few milliseconds to a few minutes and are known to be followed by an afterglow.
These bursts can span from a small distance to billions of light-years across and cannot be foreseen. Most blasts are billions of light-years away from our planet. They are also quite rare as only a handful occur every one million years or so.
Last year, a team of researchers claimed to have found evidence to suggest Earth was struck by a gigantic blast of radiation during the Middle Ages in A.D. 774 and 775. Scientists could not agree what it was, but a new study says it could have been a GRB.
The study, conducted by authors V.V. Hambaryan and R. Neuhaser, stated that the radiation could have been from the result of two black holes or neutron stars integrating in our Milky Way galaxy. Such a merger would have caused astronomical amounts of energy.
“In summary, all observables of the 14C peak in AD 774/5 are consistent with a Galactic short GRB at 1–4 kpc: sufficient energetics, correct spectrum and correct time-scale, also neither an SN nor an SNR nor a mass extinction event,” wrote the study authors in its conclusion.
Prior to this latest finding, the Ordovician–Silurian extinction event, which occurred about 450 million years ago and was the second-largest mass extinction in the Earth’s history, was to have most likely been caused by a GRB
Furthermore, the next candidate to strike Earth in the future in the form of a GRB is the Wolf-Rayet star, a gigantic star that is losing an astronomical sum of mass at a rapid pace because of strong stellar wind (2000 km/s).
If a GRB does, in fact, hit Earth then it could cause long-term destruction. Since a GRB would produce enough gas to cover and darken the sky, sunlight would not be able to reach the Earth’s surface and would lead to a cosmic winter and further degrade the ozone layer.
More about gammaray burst, Monthly Notices of the Royal Astronomical Society, Universe, Earth, 8th century
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