Middle Age Bang

Something strange happen to our planet around the year 775. Last year researchers found evidence that the Earth had been struck by a blast of radiation during the Middle Ages, but there has been debate ever since over what kind of cosmic event could have caused this. Now a study suggests it may have been the result of two black holes or neutron stars merging within our galaxy, producing what is known as a 'Gamma-ray Burst', the most violent event known to happen in the universe.

The research started when ancient cedar trees in Japan were discovered to have an unusually high level of a radioactive type of carbon known as carbon-14. In Antarctica, too, there was a spike in levels of a form of beryllium, beryllium-10, found in ice cores from deep under the surface. These can both be dated very accurately. These rare isotopes are created when intense radiation hits the atoms in the upper atmosphere, suggesting that a blast of energy had once hit the Earth from space. First thoughts were a supernova, an exploding star, may have been the culprit but then ruled out because the debris from such an event would still be visible in telescopes today, we see no such event. Then another group published a paper suggesting that an unusually large solar flare from the Sun could have been the cause. However others disagree because they do not think that the energy produced would tally with the high levels of the isotopes found. Now a group of German researchers have suggested another explanation. A massive explosion that took place within the Milky Way caused when black holes, neutron stars or white dwarfs collide. This type of mergers take just seconds, but produces a vast wave of radiation. They conclude that the event took place some 3,000 to 12,000 light-years away. That is within our own galaxy.

Dramatic as it sounds, the population of Earth at the time would not have noticed anything, such an event would not produce any visible light. However, if such an event were to happen today the result could be disastrous to modern society. If it did happen, at the same distance, it would most likely knock out satellites and affect power grids across the planet. If however such an event were to happen much closer to the Earth, say a few hundred lights years away, it could be enough to destroy the ozone layer, with devastating effects for life on the planet. Fortunately, the likelihood of such a close event is incredibly small, although not zero. Once again we are reminded of how we live in a cosmic shooting gallery.