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Earth Space Science

What Struck Earth in 775? 344

Posted by samzenpus
from the park-that-anywhere dept.
ananyo writes "Just over 1,200 years ago, the planet was hit by an extremely intense burst of high-energy radiation of unknown cause, scientists studying tree-ring data have found. The radiation burst, which seems to have hit between 774 and 775, was detected by looking at the amounts of the radioactive isotope carbon-14 in tree rings that formed during the 775 growing season in the Northern Hemisphere. The increase in 14C levels is so clear that the scientists conclude that the atmospheric level of 14C must have jumped by 1.2% over the course of no longer than a year, about 20 times more than the normal rate of variation (abstract). Yet, as the only known events that can produce a 14C spike are supernova explosions or giant solar flares, and neither event was observed at the time, astronomers have a cosmic mystery on their hands."
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What Struck Earth in 775?

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  • Re:Behind the Sun? (Score:3, Informative)

    by Anonymous Coward on Monday June 04, 2012 @09:08AM (#40207767)

    If there was a supernova around then, then there would be remnents of a supernova that we could date back to then, right? We would be able to observe the remnents today and work back to about when that particular star died, even if it wasn't observed back in 775, right?

  • Aliens! (Score:4, Informative)

    by oneiros27 (46144) on Monday June 04, 2012 @09:16AM (#40207851) Homepage

    Lister: Your explanation for anything slightly peculiar is aliens, isn't it? You lose your keys, it's aliens. A picture falls off the wall, it's aliens. That time we used up a whole bog roll in a day, you thought that was aliens as well.
    Rimmer: Well we didn't use it all, Lister. Who did?
    Lister: Rimmer, *aliens* used our bog roll?
    Rimmer: Just cause they're aliens doesn't mean to say they don't have to visit the little boys' room. Only they probably do something weird and alien-esque, like it comes out of the top of their heads or something.

    --Red Dwarf, "Kryten"

  • by vlm (69642) on Monday June 04, 2012 @09:23AM (#40207911)

    Would this mean carbon dating is inaccurate for items older than 1300 years?

    Things that were alive in 775 appear to have more C14 than usual, so even after centuries of decay, they'd still have more C14 than usual, which would make them measure younger. This is my understanding from reading the "Amateur Scientist" column in "Scientific American" about doing radiocarbon dating at home. SciAm used to be a pretty cool magazine, well, 50 years ago. When I was a high school kid I spent about two weeks one summer reading on microfilm pretty much every Amateur Scientist column from the 30s (when it was all telescopes) until the 70s when it started sucking. You can buy a collection of those columns on a cdrom now, of course.

    Time to redate the Shroud of Turin?

    I'm not up on my mythology, but I think it's made of woven plant or animal fibers, and this would have no effect unless the plants or animals that made it were alive in 775. If it was grown in 775, then it would be misdated to be somewhat younger. I might misremember but isn't the mythology something along the lines that it was grown just a short time before year 0 ? This error is going in the opposite direction then. Or theres some alternate mythology as regards templars and freemasons and such, which is too recent to be fixed by the error.

    Or the TLDR summary version of the above is ... "no, and no".

  • Re:Behind the Sun? (Score:5, Informative)

    by smooth wombat (796938) on Monday June 04, 2012 @09:45AM (#40208095) Homepage Journal
    Can you see ANY nebula in the night sky with your eyes?

    Yes, there are. Orion, Pipe, Eta Carinae and Coal Sack are four you can see with the naked eye. Granted, the people back then wouldn't have known they were nebulas, but those objects were still visible in the night sky.
  • by SirGarlon (845873) on Monday June 04, 2012 @09:49AM (#40208141)

    Are there any detailed written astronomical observations from the southern hemisphere from that long ago?

    In 775 the Maya [wikipedia.org] were almost certainly making astronomical observations. In the Eastern Hemisphere, I had to Google a bit but the Srivijaya [wikipedia.org] Empire would have had a strong interest in astronomy for navigational purposes. But neither the Maya nor the Srivijaya civilizations have near as many surviving records as do European or Chinese civilizations of the same period.

  • Re:Behind the Sun? (Score:5, Informative)

    by bigrockpeltr (1752472) on Monday June 04, 2012 @09:57AM (#40208219)
    M42 (Great Nebula in Orion) is clearly visible with the naked eye even in fairly light polluted areas. Also, people have reported seeing at least one supernova with the naked eye from back in those days when light pollution was essentially zero. but you are right about not being able to notice a SN if it was only visible during the day.
  • well (Score:5, Informative)

    by JustOK (667959) on Monday June 04, 2012 @10:10AM (#40208359) Journal

    A.D. 774. This year the Northumbrians banished their king,
    Alred, from York at Easter-tide; and chose Ethelred, the son of
    Mull, for their lord, who reigned four winters. This year also
    appeared in the heavens a red crucifix, after sunset; the
    Mercians and the men of Kent fought at Otford; and wonderful
    serpents were seen in the land of the South-Saxons.

    http://omacl.org/Anglo/part2.html [omacl.org]

  • by goodmanj (234846) on Monday June 04, 2012 @10:20AM (#40208481)

    No, scientists have known for a long time that the 14C creation rate isn't quite constant, and have taken this into account in order to do accurate radiocarbon dating. In fact, it was by looking at this carbon-dating calibration curve that they first noticed something unusual in 775.

    http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11123.html [nature.com]

  • by Anonymous Coward on Monday June 04, 2012 @10:30AM (#40208593)

    Richardcm posted this on reddit:

    "[The Anglo-Saxon Chronicle](http://omacl.org/Anglo/part2.html) gives this curious entry for the year 774: A.D. 774. ... This year also appeared in the heavens a red crucifix, after sunset; the Mercians and the men of Kent fought at Otford; and wonderful serpents were seen in the land of the South-Saxons.
    The Anne Savage translation says 'Men saw Christ's red cross in the heavens after sunset' but in the year 776." Interesting, and noteworthy.

  • Re:Behind the Sun? (Score:4, Informative)

    by Lumpy (12016) on Monday June 04, 2012 @10:46AM (#40208781) Homepage

    Unfortunately M42 is not visible from around here, and most people cant spot it until it is pointed out, even in low light pollution areas. People in general dont notice. But the trained eye certainly can, like you point out.

    But, IT would have to be brighter than -2.5 to be seen from Earth during full daylight. Anything near the sun within several sun widths would have to be ungodly bright to even be noticed. Even during a 2 month period a close supernovae would be unnoticed. The could would not stay at -2.5 for very long, so even if it was a super bright -1 it would be close to 6 months before it would swing around into twilight.

    You could have a 4.5 month period of not being able to see it. Plenty of time for a distant one to dim considerably.

  • Re:Solar telescopes? (Score:4, Informative)

    by CanHasDIY (1672858) on Monday June 04, 2012 @10:46AM (#40208787) Homepage Journal

    Where people making observations of the Sun in 775?

    Considering that the Camera Obscura [wikipedia.org] dates back to at least 400 BCE, I would say yes, yes there were.

  • by goodmanj (234846) on Monday June 04, 2012 @10:54AM (#40208859)

    I had a geologist roommate once... I know just enough about geology to be really dangerous (like programmer with screwdriver)

    Yeah, this probably won't work. Magnetostratigraphy typically gives you information about changes taking place over the timescale that rock formations are created -- millions of years. Those seafloor magnetic field stripes are 100,000 to a million years wide.

    That said, if you found a place with intense, continuous volcanic activity, like Hawaii or Iceland, you might be able to find a series of lava flows the right age that would preserve the magnetic field data. The problem would be precisely dating the lava flows -- you can't use 14C dating for that.

  • Re:Behind the Sun? (Score:5, Informative)

    by pla (258480) on Monday June 04, 2012 @11:10AM (#40209055) Journal
    If the supernova was behind or near the Sun, earthlings around 775 wouldn't have been able to detect it.

    Nearby supernovae appear as one of the brightest objects in the sky for a few days to a week. The remnants remain visible for months, and then have a habit of leaving a nebula behind.

    The Earth travels slightly more than one degree of its orbit per day; The Sun, as seen from the Earth, subtends half a degree of arc. In the absolute worst case, the sun couldn't completely "hide" a supernova for more than a single day; and half a week later, the supernova remnant would dominate the dusk (or dawn) as the brightest thing in the sky except possibly the moon.

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