Astronomers Investigating Unknown Object That Hit the Earth In 773 AD

KentuckyFC writes "In November 2012, a group of Japanese scientists discovered that the concentration of carbon-14 in Japanese cedar trees suddenly rose between 774 AD and 775 AD. Others have since found similar evidence and narrowed the date to 773 AD. Astronomers think this stuff must have come from space so now the quest is on to find the extraterrestrial culprit. Carbon-14 is continually generated in the atmosphere by cosmic rays hitting nitrogen atoms. But because carbon-14 is radioactive, it naturally decays back into nitrogen with a half-life of about 5700 years. This constant process of production and decay leaves the amount of carbon-14 in the atmosphere relatively constant at about one part in a trillion will be carbon-14. One possible reason for the increase is that the Sun belched a superflare our way, engulfing the planet in huge cloud of high energy protons. Recent calculations suggest this could happen once every 3000 years and so seems unlikely. Another possibility is a nearby supernova, which bathed the entire Solar System in additional cosmic rays. However, astronomers cannot see any likely candidates nearby and there are no historical observations of a supernova from that time. Yet another possibility is that a comet may have hit the Earth, dumping the extra carbon-14 in the atmosphere. But astronomers have ruled that out on the basis that a comet carrying enough carbon-14 must have been over 100 km in diameter and would surely have left other evidence such as an impact crater. So for the moment, astronomers are stumped."

Why unlikely?

[Anonymous Coward]

"Recent calculations suggest this could happen once every 3000 years and so seems unlikely."

Why would it seem unlikely, that at some point 1300 years ago, an event calculated to happen every 3000 years actually happened?

Article says Not so Unlikely

[glennrrr]

"There was a time when astronomers would have immediately ruled out this possibility as well. But last year, astrophysicists calculated that sun-like stars can produce superflares of this size about once every 3000 years."

I think that if an event happened 14 centuries ago, and one explanation is supposed to happen every 30 centuries or so then it isn't something that can be discarded as an explanation without further evidence.

Misleading title

[daitengu]

While we're arguing about solar flares, or supernovas, we're kind of ignoring the obvious. The title states "an unknown object" "hit the earth". That, also, is ruled out right in the article.

Maybe a better title would have been "Some shit happened in 773 AD and no one really knows what it is, but here's what we have so far!"

Re:Misleading title

[ColdWetDog]

Maybe a better title would have been "Some shit happened in 773 AD and no one really knows what it is, but here's what we have so far!"

Don't quit your day job to be a headline copy editor.