8th century gamma ray burst irradiated the Earth, study finds

Jan 21, 2013
An artist's impression of the merger of two neutron stars. Short duration gamma-ray bursts are thought to be caused by the merger of some combination of white dwarfs, neutron stars or black holes. Theory suggests that they are short lived as there is little dust and gas to fuel an 'afterglow'. Credit: Part of an image from NASA / Dana Berry.

(Phys.org)—A nearby short duration gamma-ray burst may be the cause of an intense blast of high-energy radiation that hit the Earth in the 8th century, according to new research led by astronomers Valeri Hambaryan and Ralph Neuhӓuser. The two scientists, based at the Astrophysics Institute of the University of Jena in Germany, publish their results in the journal Monthly Notices of the Royal Astronomical Society.

In 2012 scientist Fusa Miyake announced the detection of high levels of the isotope Carbon-14 and Beryllium-10 in formed in 775 CE, suggesting that a burst of radiation struck the Earth in the year 774 or 775. Carbon-14 and Beryllium-10 form when radiation from space collides with , which then decay to these heavier forms of carbon and . The earlier research ruled out the nearby explosion of a massive star (a supernova) as nothing was recorded in observations at the time and no remnant has been found.

Prof. Miyake also considered whether a could have been responsible, but these are not powerful enough to cause the observed excess of carbon-14. Large flares are likely to be accompanied by ejections of material from the Sun's corona, leading to vivid displays of the northern and southern lights (aurorae), but again no historical records suggest these took place.

Following this announcement, researchers pointed to an entry in the Anglo-Saxon Chronicle that describes a 'red crucifix' seen after sunset and suggested this might be a supernova. But this dates from 776, too late to account for the carbon-14 data and still does not explain why no remnant has been detected.

Drs. Hambaryan and Neuhӓuser have another explanation, consistent with both the carbon-14 measurements and the absence of any recorded events in the sky. They suggest that two compact stellar remnants, i.e. , or , collided and merged together. When this happens, some energy is released in the form of gamma rays, the most energetic part of the electromagnetic spectrum that includes visible light.

In these mergers, the burst of gamma rays is intense but short, typically lasting less than two seconds. These events are seen in other galaxies many times each year but, in contrast to long duration bursts, without any corresponding visible light. If this is the explanation for the 774 / 775 radiation burst, then the merging stars could not be closer than about 3000 light years, or it would have led to the extinction of some terrestrial life. Based on the carbon-14 measurements, Hambaryan and Neuhӓuser believe the gamma ray burst originated in a system between 3000 and 12000 light years from the Sun.

If they are right, then this would explain why no records exist of a supernova or auroral display. Other work suggests that some visible light is emitted during short gamma-ray bursts that could be seen in a relatively nearby event. This might only be seen for a few days and be easily missed, but nonetheless it may be worthwhile for historians to look again through contemporary texts.

Astronomers could also look for the merged object, a 1200 year old black hole or neutron star 3000-12000 light years from the Sun but without the characteristic gas and dust of a supernova remnant.

Dr Neuhӓuser comments: "If the had been much closer to the Earth it would have caused significant harm to the biosphere. But even thousands of light years away, a similar event today could cause havoc with the sensitive electronic systems that advanced societies have come to depend on. The challenge now is to establish how rare such Carbon-14 spikes are i.e. how often such radiation bursts hit the Earth. In the last 3000 years, the maximum age of trees alive today, only one such event appears to have taken place."

Explore further: 'Blockbuster' science images

More information: The team's paper will be published online in the Oxford University Press journal Monthly Notices of the Royal Astronomical Society at 9am on Monday 21 January. The paper will be available via mnras.oxfordjournals.org/conte… 08/mnras.sts378.full . A preprint of the paper can be seen at xxx.lanl.gov/abs/1211.2584

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alfie_null
5 / 5 (2) Jan 21, 2013
I can't imagine what it would be like to "see" a collision, but I wonder how fanciful the illustration is.
For instance, given the gravity it seems unlikely large chunks would be knocked loose. Allowing that stuff could be knocked loose, it would be as dust, due to tidal stress?
ritwik
5 / 5 (3) Jan 21, 2013
http://omacl.org/...rt2.html

i looked up in anglo saxon chronicle available online.it just there
IronhorseA
3.4 / 5 (5) Jan 21, 2013
"But this dates from 776, too late to account for the carbon-14 data and still does not explain why no remnant has been detected"

From the Anglo Saxon Chronicle:

"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."

They must have misread the date of the entry.
Telekinetic
1 / 5 (4) Jan 21, 2013
A little stale even for physorg:

http://www.scient...ky-774ad
jscroft
1.4 / 5 (30) Jan 21, 2013
Talk about an Act of G-d! Much closer and an entire hemisphere fries. Much closer than that and the planet is sterilized, game over.

All you wacko environmentalists, consider this: one of the kinds of evil progress hampered by all your bitching and moaning is the distribution of Earth's biome--humans AND polar bears, dimwits!--far enough throughout space that your precious Gaea can actually SURVIVE a natural event that would sterilize her home planet.

See, the Fermi Paradox has answers far darker than Singularity. Chilling.
jscroft
1.4 / 5 (11) Jan 21, 2013
Also a great motivator for figuring out how to build a working gravity wave detector, as this is probably the only way reasonably accessible to us now of getting out in front of an impending GRB.
VendicarD
2.9 / 5 (19) Jan 21, 2013
Greed and ignorance know no bounds.

"All you wacko environmentalists" - jscroft

jscroft provides an abundance of both.

The world will become intellectually and morally superior with his passing.

VendicarD
2.4 / 5 (14) Jan 21, 2013
jscroft should consider how he would react if the machine replacements we are currently developing for ourselves were as disrespectful of human life as he is toward the rest of the Biosphere.

"the Fermi Paradox has answers far darker than Singularity." - jscroft

Morality demands the extinction of corrupt and immoral ideologies like the one held by jscroft.
jscroft
2.4 / 5 (20) Jan 21, 2013
Scott, you are a fool.

The point of the Fermi Paradox comment was that we may not be hearing from our neighbors because they are periodically exterminated by GRBs.

Meanwhile...

>> The world will become intellectually and morally superior with his passing.

Big talk, tough guy. One wonders how brave you are outside Mom's basement.
cantdrive85
1.6 / 5 (20) Jan 21, 2013
Their cavalier dismissal of a large solar flare or CME may be flawed, it is far more likely than this silly hypothesis of a neutron star collision;
http://www.thunde...sfire-2/
ryggesogn2
2.1 / 5 (11) Jan 21, 2013
How do such events impact the calibration of C14, or any other isotopic dating method?
jscroft
2.6 / 5 (10) Jan 21, 2013
Their cavalier dismissal of a large solar flare or CME may be flawed, it is far more likely than this silly hypothesis of a neutron star collision


Don't know how silly it is. My guess is that a high-frequency, enormously high-amplitude GRB would have a recognizably different impact on C isotopes than a CME. In fact, not entirely convinced that a CME would have ANY measurable effect 1000 years later. Not that I've really looked into it.

How do such events impact the calibration of C14, or any other isotopic dating method?


Interesting question, but my guess would be not much. Remember the GRB flux is very powerful but only lasts a few minutes.
rkolter
5 / 5 (10) Jan 21, 2013
Also a great motivator for figuring out how to build a working gravity wave detector, as this is probably the only way reasonably accessible to us now of getting out in front of an impending GRB.


I don't understand this statement. Gamma Rays are a form of EM radiation and move at the speed of light. How is a gravity wave detector going to give us advance notice (what I read from 'get out in front of') of an impending GRB? Gravity doesn't move faster than the speed of light.
jscroft
3.7 / 5 (15) Jan 21, 2013
Also a great motivator for figuring out how to build a working gravity wave detector, as this is probably the only way reasonably accessible to us now of getting out in front of an impending GRB.


I don't understand this statement. Gamma Rays are a form of EM radiation and move at the speed of light. How is a gravity wave detector going to give us advance notice (what I read from 'get out in front of') of an impending GRB? Gravity doesn't move faster than the speed of light.


Neutron stars and other degenerate objects in close orbit are (at least in theory) a major source of gravity-wave signals. During the days or weeks prior to collision, I would anticipate that the GW signal would increase dramatically in frequency (as orbital decay causes the orbit frequency to increase) and amplitude (just a guess).

Odds are this effect could furnish some kind of early warning of the impending GRB, if only we could detect it.
icuvd
3.5 / 5 (8) Jan 21, 2013
Also a great motivator for figuring out how to build a working gravity wave detector, as this is probably the only way reasonably accessible to us now of getting out in front of an impending GRB.


I don't understand this statement. Gamma Rays are a form of EM radiation and move at the speed of light. How is a gravity wave detector going to give us advance notice (what I read from 'get out in front of') of an impending GRB? Gravity doesn't move faster than the speed of light.

A gravity wave detector could in theory detect an impending collision of 2 massive bodies (say 2 neutron stars) by the increasing frequency of the GW's as the 2 objects orbit each other closer and closer until they collide.
rkolter
5 / 5 (4) Jan 21, 2013
Ahh. Thank you for the follow-up. I was thinking about detecting the gravity waves created by converting a small portion of the colliding bodies mass into energy. I was not thinking about the pattern generated by the two objects prior to collision.
VendicarD
2.6 / 5 (10) Jan 21, 2013
Yes, that was self evident.

"The point of the Fermi Paradox comment was that we may not be hearing from our neighbors because they are periodically exterminated by GRBs." - jscroft

Why do you think that your unnecessary attempt to clarify your meaning in any way alters the immorality of your statement?
VendicarD
3 / 5 (10) Jan 21, 2013
While I sympathize, I note that your claim is just supposition.

"Gravity doesn't move faster than the speed of light." - Rkolter

The speed of gravity has not been measured.
VendicarD
2 / 5 (12) Jan 21, 2013
They don't since there is no definitive record of any such event.

"How do such events impact the calibration of C14, or any other isotopic dating method?" - RyggTard

Your question reeks of scientific ignorance, and if you were capable of learning that would be acceptable coming from an intellectual inferior such as yourself.

But you have proven yourself to be incapable of learning.
icuvd
3.4 / 5 (5) Jan 21, 2013
Ahh. Thank you for the follow-up. I was thinking about detecting the gravity waves created by converting a small portion of the colliding bodies mass into energy. I was not thinking about the pattern generated by the two objects prior to collision.

A gravity wave detector may work but would almost always lead to a false alarm as the GW's propagate in all directions but the GRB is highly directional and any going off in our galaxy has very small probability of being aimed at us!
VendicarD
2.8 / 5 (10) Jan 21, 2013
"One wonders how brave you are outside Mom's basement." - jscroft

Post your address and I'll pop over for a visit. I'll bring you some muffins and a coffee, and then you can see for yourself.

"A gravity wave detector may work" - jcuvd

You forget that gravity waves will be primarily emitted along the plane of rotation of the binary pair, but the gamma rays will be directed mostly perpendicular to that plane.
icuvd
2.3 / 5 (3) Jan 21, 2013
You forget that gravity waves will be primarily emitted along the plane of rotation of the binary pair, but the gamma rays will be directed mostly perpendicular to that plane.

Read more at: http://phys.org/n...html#jCp

You are of course correct in pointing that out. I believe my premise that a GW detector would lead to a high false alarm rate is still valid.
rkolter
5 / 5 (9) Jan 21, 2013
"Gravity doesn't move faster than the speed of light." - Rkolter

The speed of gravity has not been measured.

I don't know if the speed of gravity has been measured or not. I do know that that for the laws of physics as we understand them and the universe as we know it to be valid, the speed of gravity can't be faster than the speed of light.

If it turns out to be otherwise, look me up and I will buy you a beer.
VendicarD
2.8 / 5 (9) Jan 21, 2013
Hence my sympathy.

"I do know that that for the laws of physics as we understand them and the universe as we know it to be valid, the speed of gravity can't be faster than the speed of light. " - Rkolter

How fast to entangled wave functions disentangle?

The speed of light is infinite between scattering events.
Caliban
3.3 / 5 (3) Jan 21, 2013
You forget that gravity waves will be primarily emitted along the plane of rotation of the binary pair, but the gamma rays will be directed mostly perpendicular to that plane.

Read more at: http://phys.org/n...html#jCp

You are of course correct in pointing that out. I believe my premise that a GW detector would lead to a high false alarm rate is still valid.


Given that the gravity waves and GRBs produced by such an event would be normal to eachother, it seems that we wouldn't receive any warning at all via gravity wave detection of an incoming GRB, since the gravity waves would be propagating at 90degrees relative to the GRB, and thus be undetectable here on Earth.

RealScience
5 / 5 (2) Jan 21, 2013
How do such events impact the calibration of C14, or any other isotopic dating method?


@ryggesogn2: It wouldn't have much impact on dating other than C14 dating (potassium/argon, uranium etc. would not be affected).

For C14 dating such events make object formed after the even look younger than the are. The 774/775 AD event was a 1.2% spike in C14, which would make plant matter that grew in 775 look 100 years younger than it is (~1150 years old instead of ~1250).

The effect diminishes fairly rapidly as atmospheric carbon is drawn down by plants and new carbon is added from decomposition; plant matter formed in 780 AD would appear ~50 years younger than it is, etc.
Such events in the last few thousand years can be found through tree rings (as this one was) and then compensated for.
RealScience
4.3 / 5 (6) Jan 21, 2013
@Vendicar - JSCroft's comment is on saving the biosphere, so that is hardly disrespectful to the biosphere.

@JSCroft - your comment is disrespectful to environmentalists. Many environmentalists support space research and not being bound to one vulnerable planet, just as you do, so why insult them?
Your comment was valid, but the baggage that you saddled it with was counterproductive.
cantdrive85
1 / 5 (9) Jan 21, 2013
"Gravity doesn't move faster than the speed of light." - Rkolter

The speed of gravity has not been measured.

I don't know if the speed of gravity has been measured or not. I do know that that for the laws of physics as we understand them and the universe as we know it to be valid, the speed of gravity can't be faster than the speed of light.

If it turns out to be otherwise, look me up and I will buy you a beer.

The Earth doesn't orbit where the Sun was 8 minutes ago, it must orbit where it is now. In that vein, Pluto doesn't orbit where the Sun was 6 hours ago, if it did Pluto would be flung out of the solar system within a few thousand years.
VendicarD
5 / 5 (7) Jan 21, 2013
Actually it is thought to do just that.

"The Earth doesn't orbit where the Sun was 8 minutes ago" - CantDrive

But it hasn't been measured.

Observation of frame dragging is as close as observation has come to indirectly measuring the speed of gravity, and here only through the observed consistency of observation with GR.

So, there is more than suspicion.

VendicarD
5 / 5 (6) Jan 21, 2013
Well........ No.

"if it did Pluto would be flung out of the solar system within a few thousand years." - CantDrive

The angular separation between where the center of the sun is now and where it will be in a few hours represents only a minute fraction of a degree at the distance of Pluto.

We also know that the time interval of the arrival of gravity should be proportional to the distance from the sun, as will be the subtended angle through which the sun changes position as observed at Pluto, or any distance, so to a first approximation the effect is the same regardless of distance from the sun.

GR is required to compute the difference.
cantdrive85
1.6 / 5 (9) Jan 21, 2013
In the time it takes the Sun's light to arrive at Earth, the Sun will have traveled almost 100,000km toward it's north pole. It will have traveled 4,000,000km by the time it arrives at Pluto. Yet, the planets remain in their position in relation to the ecliptic while orbiting the Sun. If gravity was not nearly instantaneous on the solar system scale, the Sun would have left us behind long ago.
VendicarD
5 / 5 (5) Jan 21, 2013
Your presumption is that the sun is pulling pluto along for the ride.

This is not the case.

"In the time it takes the Sun's light to arrive at Earth, the Sun will have traveled almost 100,000km toward it's north pole." - Cantdrive

Pluto condensed out of the same cloud of dust as the sun and therefore shares the same or nearly the same velocity that the sun has with respect to the rest of the galaxy, or other objects that are farther away.

There is a small differential force the sun feels while Pluto does not due to the relative positions of both objects with respect to distant objects.

That differential force is well within the Newtonian realm and will produce no substantive difference due to the presumed speed of gravity.
Whydening Gyre
2.3 / 5 (6) Jan 21, 2013
This has been an extremely interesting Article posting in that the conversations have been very informative and, well - civil.
I have made comment on other articles that were declaratory simplifications that were rather obvious in afterthought.
Please allow that this is a direct result of becoming an an old dog still attempting to learn new tricks.
From now on I will attempt only to observe and learn - not simplify.
Whydening Gyre
1 / 5 (5) Jan 21, 2013
In the time it takes the Sun's light to arrive at Earth, the Sun will have traveled almost 100,000km toward it's north pole.

I am not getting why the Sun travels towards its north pole, against it's rotational axis. Can you please clarify?
cantdrive85
1.6 / 5 (7) Jan 21, 2013
The Sun's ecliptic is at least 60 degrees off kilter to the galactic plane (ecliptic). The relative motion of the Sun is through it's north pole, that is to say the leading edge of the Sun is it's north pole. The rotation of the Sun follows the right-hand rule. It's a bit of a fallacy that the planets orbit the Sun in circular or elliptical orbits, in reality if you trace the orbits they would be spiral or helical in nature. In addition to that, the Sun itself actually traces out a spiral path, it's not on a bullet type trajectory, so to speak.
VendicarD
3.7 / 5 (3) Jan 21, 2013
The entire solar system is moving roughly in the direction of the constellation Hercules.

This has no measurable implication to the speed of gravity.
thingumbobesquire
3 / 5 (2) Jan 22, 2013
We are currently striving to establish the means to prevent collisions with comets, etc. But this type of potential event (and worse,) rare though it is, certainly would seem to merit some consideration regarding safeguarding life.
rubberman
2.6 / 5 (5) Jan 22, 2013
Guys. Galileo called it an inertial reference frame. Our sun, and everything orbiting it share a common one. CD, we have been over this before, the orbit is helical from a fixed point in the universe, so as I responded before...find one. The entire portion of the Orion arm of the galaxy which we are part of oscillates between hemispheres of the galactic plane, I believe it's twice every (once each direction) every 100 million years. This transition between hemispheres, combined with the primer fields model of galactic magnetic fields and the 60 degree inclination to the ecliptic of our system, provide a very convincing mechanism for the oddball pattern and timing of the earths magnetic pole flips. That said, if we are in the path of cosmic ray jets, they will be the first thing to arrive at earth. Any other disturbance the we can detect would follow....
jscroft
1.8 / 5 (5) Jan 22, 2013
@JSCroft - your comment is disrespectful to environmentalists. Many environmentalists support space research and not being bound to one vulnerable planet, just as you do, so why insult them?
Your comment was valid, but the baggage that you saddled it with was counterproductive.


Not unfair. Is it also not unfair to point out that I specifically addressed the "wacko" ones? :)
rkolter
5 / 5 (3) Jan 22, 2013
"I do know that that for the laws of physics as we understand them and the universe as we know it to be valid, the speed of gravity can't be faster than the speed of light. " - Rkolter

How fast to entangled wave functions disentangle?

The speed of light is infinite between scattering events.

I don't know any scientist with a basic grasp of relativity that would say the speed of light "becomes infinite". But if it did... gravity cannot move faster than 'infinite'. QED.

If the graviton is massless, then it moves at the speed of light. E=cP. If it is not massless, then it moves at some speed less than the speed of light, because the energy required to accelerate a particle with mass to the speed of light is infinite.

We do not need to measure the speed of gravity to identify that gravity cannot move faster than the speed of light.
rkolter
5 / 5 (2) Jan 22, 2013
How fast to entangled wave functions disentangle?

While entangled wave functions collapse potentially with infinite speed, the information about that collapse does not exceed the speed of light.

You and I are a lightyear apart, each with an entangled particle. Your measurement collapses the wave function. You radio me the result. I need that result to verify the wave function collapsed. It takes a year to arrive.

EVEN if you and I agree that there is a 1 lightyear distance between us beforehand, and you radio me saying, "Ten minutes after you get this, I will collapse the wave function!" The information about the wave function collapsing will still take a YEAR to get to me.

Even if you tell me before I board my ship, that you will collapse the function ten minutes after I get to my destination one light year out - from your frame of reference it will take a year at the VERY MINIMUM before I can measure my particle at my destination and verify the result.
jscroft
2.1 / 5 (7) Jan 22, 2013
You forget that gravity waves will be primarily emitted along the plane of rotation of the binary pair, but the gamma rays will be directed mostly perpendicular to that plane.


Scott. Wonders abound... apparently a blind squirrel CAN find a nut if it roots around long enough in Mom's basement! I stand corrected.

Er... are gravity waves subject to polarization? Would the decaying orbit emit a weaker signal along the mutual orbital axis, but rotationally polarized?

Regarding tea & cookies, tough guy: There's this thing called the Internet. Surely we can arrange a meeting without exposing our contact details to the world.
rubberman
1 / 5 (4) Jan 22, 2013
"Er... are gravity waves subject to polarization?"

If gravity works as induced magnetism by a large field source on every atom within it's sphere of influence...I would say gravity is polarizing force.
Caliban
5 / 5 (2) Jan 22, 2013

Regarding tea & cookies, tough guy: There's this thing called the Internet. Surely we can arrange a meeting without exposing our contact details to the world.


Nah -keep it public.

If the contest occurs close enough to my neck of the woods, I'd be delighted to attend. Each combatant, upon completion of said dispute, will receive a pint of stout, which I will purchase at my own expense. I will also have salt for the loser's wounds.

rubberman
3 / 5 (6) Jan 22, 2013

Regarding tea & cookies, tough guy: There's this thing called the Internet. Surely we can arrange a meeting without exposing our contact details to the world.


Nah -keep it public.

If the contest occurs close enough to my neck of the woods, I'd be delighted to attend. Each combatant, upon completion of said dispute, will receive a pint of stout, which I will purchase at my own expense. I will also have salt for the loser's wounds.



I'll bring my hat that holds 2 king cans...and spring for pizza. The tea and cookies can be dessert.
rkolter
5 / 5 (2) Jan 22, 2013

Regarding tea & cookies, tough guy: There's this thing called the Internet. Surely we can arrange a meeting without exposing our contact details to the world.


Nah -keep it public.

If the contest occurs close enough to my neck of the woods, I'd be delighted to attend. Each combatant, upon completion of said dispute, will receive a pint of stout, which I will purchase at my own expense. I will also have salt for the loser's wounds.



I'll bring my hat that holds 2 king cans...and spring for pizza. The tea and cookies can be dessert.

I have a little slice of beach I can offer up if we need a venue...
jscroft
1 / 5 (3) Jan 23, 2013
Haha is it anywhere near Chicago? Scott's mom can finally fumigate that basement, and we can all feast on BBQ troll.

Whaddaya say, Scott? Lets have a dance on the beach, Marine Corps style! Frigging Tard.
jselin
5 / 5 (2) Jan 25, 2013
If the gravity wave signal approaches zero at the axis of rotation in a predictable way then a constellation of three or more detectors sent out into space might be able to calculate where the GRB is pointed. The detection range would probably be limited by their relative spacing and their sensitivity but the closer threats should be easier to detect.
jscroft
1.8 / 5 (5) Jan 25, 2013
If the gravity wave signal approaches zero at the axis of rotation in a predictable way then a constellation of three or more detectors sent out into space might be able to calculate where the GRB is pointed. The detection range would probably be limited by their relative spacing and their sensitivity but the closer threats should be easier to detect.


Makes sense. Although I get the directional nature of the GRB pulse, I don't really have a good idea of how narrow the beam is. My guess would be not very, if the geometry is at all similar to pulsar beams.

Maybe a dead-center hit would be minimally detectable, but it would also be minimally likely. Given the extreme damage one of those things could do, seems it would be worthwhile at least figuring out how common they really are.

A detector array like the one you described would probably be the ideal tool for doing that.
Graeme
5 / 5 (4) Jan 27, 2013
There should be also he effects on the other bodies in the solar system. The moon and asteroids should also have radioactive isotopes from a heavy GRB irradiation. Since it only lasts a minute, there should be a clear shadow in the radiation. This would show which face was towards the burst. When combined with several spinning bodies (perhaps including other moons) the exact date should be able to be determined, as well as the rough time and direction to within a couple of degrees.
RealScience
5 / 5 (2) Jan 27, 2013
@Graeme: great suggestion - it just might work.

It wouldn't be easy. Bodies without atmospheres would have sharp shadows for that one event, but without a rich supply of nitrogen the amount of C14 and Be10 would be tiny.
Other isotopes would be produced, but long-lived isotopes would be masked by more accumulated bombardments and short-lived isotopes would have decayed already.
But there should be some isotopes produced in typical rock that would have a half-life between a few hundred and a few thousands of years.

jscroft
1 / 5 (3) Jan 28, 2013
@Graeme: great suggestion - it just might work...


Also worth pointing out that this technique might provide useful forensic data but would not help solve the early-warning problem.
thedragonbornDovakin
not rated yet Feb 06, 2013
If these bursts last no longer than 2 seconds, would the effect not only be found in half of the world? Only the side facing the burst when it arrives would be exposed, no?
triclon
3 / 5 (2) Feb 07, 2013
Here's a little something I tried to try to locate a possible gamma ray source. Of course I am making a lot of assumptions here so take it with a grain of salt.

Assuming the gamma ray source was located at the zenith (directly overhead) in Japan in the year 774, this sweeps an arc across the sky at declination (for the year 774, taking into account the precession of the earth's tilt) of ~32 degrees. Assuming that the gamma ray source originates from the galactic plane, this arc intersects the galactic plane in two locations at approximately (in modern J2000 coordinates)
- RA: 20:09 Dec: 36:50 in the constellation Cygnus
- RA: 06:00 Dec: 37:14 in the constellation Auriga

It is interesting to note that the well known black hole candidate Cygnus X1 is located at:
RA: 19:58:22 Dec: 35:12:05
which is surprisingly close to the first intersection point stated above.
triclon
3 / 5 (2) Feb 07, 2013
Here's a little something I tried to try to locate a possible gamma ray source. Of course I am making a lot of assumptions here so take it with a grain of salt.

Assuming the gamma ray source was located at the zenith (directly overhead) in Japan in the year 774....


I forgot to mention the trees for this article's measurement are in Japan, and Cyg X-1 is 2 kiloparsecs away, within the range of paper's predicted distances of the gamma ray source.

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