Why Did High Energy Particles Shower Earth In The Year 774?
The one thing everyone can agree on is that something strange happened in the year 774, and that whatever it was sent a burst of high-energy particles into the Earth's atmosphere. Exactly what that event was, however, has remained the subject of contention. And it's back in the news today, with a new study pointing the finger at a rare event called a short gamma-ray burst.
The reason for the part that people agree on is an unusually large spike in the amount of radioactive carbon found in tree rings that have been dated back to 774. That apparently is correlated with the timing of a surge in a specific isotope of beryllium, detected in ice cores of Antarctica. Both of these isotopes are the product of collisions that take place in our atmosphere, produced by energetic particles striking some of the gasses normally resident there.
The obvious candidate, and the one that got everyone excited, was a nearby supernova. Unfortunately, supernovae that are close enough tend to be rather obvious. With a single exception (a mention of a "red crucifix" in the skies over Britain), nobody seems to have noticed anything unusual. Even more problematic, most supernovae leave a remnant, comprised of a hot, expanding cloud of material, with either a neutron star or black hole at its center. We've now done whole-sky surveys in the X-ray part of the spectrum, and we've not seen a remnant at the right age and distance.
That's where things stood late last year, when a group of scientists caught a basic logical flaw in the initial research. The original description of the isotope anomaly ruled out the Sun because it doesn't have big enough eruptions of energetic particles. But the calculations assumed the eruption would have been spread evenly in all directions; the Sun's eruptions are actually directional, so the total energy involved in the event is much smaller.
It's amazing to me that scientists can reconstruct something that happened in 774.
By comparison, I sometimes have trouble remembering what I did last night.
either your ISP or the police could probably reconstruct last night for you. =p
I'd rather ask the scientists. :)
Back to the original story, if it wasn't a nearby supernova but it WAS some great source of energy, there's potentially a lot we can learn from it.
Man do we live in interesting times...