Questions Regarding Gamma Ray Bursts (And Their Damage To Terra Firma)

[Borealis]

Greetings, good people!

 

I have some questions regarding gamma ray bursts that no one seems to be able to answer directly, and I hope that someone here will be able to provide solid answers.

 

The topic is, as you've probably already seen, gamma ray bursts. If we imagine that a moderately powerful burst hit the Earth, killing most humans (but not all), and severely damaging the ozone layer, what would happen to human-made objects? Would gamma radiation destroy buildings, or leave them unharmed?

 

I think we can safely assume that a burst would set off a chain of fires and explosions in electric systems, but would materials like wood and brick be damaged at all by the blast itself?

 

I'm eagerly awaiting your response. :)

[newdealtn]

Here's my guess, Borealis. My understanding is that gamma rays are about the most energetic levels of radiation. It would depend on how much got to us, but if I may assume that by "moderately powerful burst" you mean an average exposure--that's the iffy part; what is average for a power that can be the most powerful force in the universe?--I think you're looking at something that would scorch the earth. A good hit, from what I've gathered, would maybe destabilize the planet structure like a direct hit from a planetary object. But if you're talking about a hit that some humans somewhere on earth could survive, I think you're talking about a burst that would damage some or most man-made objects and kill many trees but would probably spare a greater percentage of those than humans. You might want to consider how you can more precisely state your question.

 

Samm

[maddog]

Borealis,

 

There are number of points to clarify before answering you question regarding GRB:

 

1) The source: Current conventional sources for GRB are thought to be Supernova stars (upto a certain level).

2) Proximity: How near such an event as a supernova would also help to determine the intensity.

3) Target: What can do the most damage or affected by in living things is DNA on this planet. This would imply if damage is sufficient

to kill human beings, it would enough to kill all living things.

 

For example the Supernova event of 1987 was not very nearby more than 10 kparsec (> ~ 30,000 Light Years).

Second example is Crab Nebula in Cygnus which occurred in 1054 is about 100 or LY away.

 

Neither one of these killed us. The dominating thing here is these burst fall off in intensity at 1/R^2 where R is the distance.

So a burst intense enough for a massive extinction event or remove the bulk of our upper atmosphere would have to be close,

very close. Of course I've only been speaking of the conventional bursts (i.e. less than 10^18 GeV).

 

For anything greater these are more rare, we don't know how these happen.

 

To speculate if say Sirius, an A0 star would supernova (not likely), it is about 18 LY away. There might be a noticeable

uptick in cancers world-wide. I don't think this would qualify as an extinction level event (ELE - as in Deep Impact). Any other

start that might be close are mostly K5+ to M star which are mostly even smaller and less likely to even nova.

 

Which comes down to some unnatural event (contrived) such as annihilating matter to produce a GRB (electron -

positron collision produces Gamma Rays). So an explosion from such a collision of say a Kg (or 2.2 lbs) would

produce

 

E = mc^2 = 9 x 10^16 Kg m^2 / s^2 = 9 x 10^16 Joules

 

I don't currently have handy the units to convert, so approximately that is like a sizable asteroid hitting the earth

which could be an extinction event. Not currently feasible by our technology. Were this some weapon by an

invading alien culture. Enough B-movies have been made on this subject. How close to reality is inconclusive.

 

maddog

[newdealtn]

Borealis,

 

There are number of points to clarify before answering you question regarding GRB:

 

1) The source: Current conventional sources for GRB are thought to be Supernova stars (upto a certain level).

2) Proximity: How near such an event as a supernova would also help to determine the intensity.

3) Target: What can do the most damage or affected by in living things is DNA on this planet. This would imply if damage is sufficient

to kill human beings, it would enough to kill all living things.

 

For example the Supernova event of 1987 was not very nearby more than 10 kparsec (> ~ 30,000 Light Years).

Second example is Crab Nebula in Cygnus which occurred in 1054 is about 100 or LY away.

 

Neither one of these killed us. The dominating thing here is these burst fall off in intensity at 1/R^2 where R is the distance.

 

maddog

 

maddog, my only knowledge of these things is from Science Channel specials, but I was thinking that gamma ray bursts were the events that occurred when massive (galactic) black holes were feasting on a bounty of nearby materials, when they ejected focused streams from their two poles of spin. These beams are common to quasars for example. Most are quite distant but are so focused as to retain immense power over long distances, being narrow beam ejecta rather than spherical radiations like sunlight. Am I thinking about the wrong thing then?

 

Samm

[Borealis]

But then again, there isn't (as far as I know) any real distinction between high-frequency x-rays and low-frequency gamma rays ("low" being the obvious pun), and these high-energy radiations wouldn't deliver much additional heat? They would fry our CNS for sure, but inanimate matter should be left unharmed? Then again, I understand that this is a question of intensity.

 

Just to clarify, the scenario I described is highly unlikely, I know, but it's that exact scenario that fascinates me intensely, because humans might actually be around to witness the enormous effects on the atmosphere and climate under those conditions (yes, I'm writing a novel, big surprise..!)

 

Of course, only the near side would see immediate casualties; any blast not strong enough to kill all humans on the near side would never be able to penetrate to the far side of the planet. But such a "weak" blast should leave any inanimate matter unharmed?

[maddog]

maddog, my only knowledge of these things is from Science Channel specials, but I was thinking that gamma ray bursts were the events that occurred when massive (galactic) black holes were feasting on a bounty of nearby materials, when they ejected focused streams from their two poles of spin. These beams are common to quasars for example. Most are quite distant but are so focused as to retain immense power over long distances, being narrow beam ejecta rather than spherical radiations like sunlight. Am I thinking about the wrong thing then?

 

Samm

 

I believe so. Radiation of all frequencies radiates spherically. Particles can be beamed in a tight beam. To do this with light is called a laser.

 

So Gamma Ray are high frequency radiation.

 

maddog

[maddog]

But then again, there isn't (as far as I know) any real distinction between high-frequency x-rays and low-frequency gamma rays ("low" being the obvious pun), and these high-energy radiations wouldn't deliver much additional heat? They would fry our ?CNS? for sure, but inanimate matter should be left unharmed? Then again, I understand that this is a question of intensity.

CNS? <Central Nervous System> -- I'm guessing. Radiation at these frequencies would ionize most surfaces animate or not, the atmosphere, lakes, etc.

 

Of course, only the near side would see immediate casualties; any blast not strong enough to kill all humans on the near side would never be able to penetrate to the far side of the planet. But such a "weak" blast should leave any inanimate matter unharmed?

Heating the atmosphere would overcome the lack leaving the "other side" unaffected.

 

BTW, where you mention what only harms people and Not inanimate objects, you might be thinking of beams of neutrons as from a Neutron Bomb of the 70s, etc. It was experimented in theory maybe not in practice were a neutron bomb to go off, living things would be affected, though amorphous objects would be unaffected. I don't believe we ever constructed such weapons (or we won't admit it).

maddog

[Borealis]

I see. Someone on a different forum told me that such a weak blast of gamma rays should be considered about the same as x-rays when it comes to inanimate objects. So a concrete building wouldn't be blown away, to be concrete (pun definitely intended).

 

So what you're saying is that the lack of ozone would be balanced out by the increase in heat from the now unhindered sunrays?

[Cyberia]

Gamma rays if sufficient will kill all humans, animals, etc. Animals that live some distance underground may survive longer though with contaminated water soaking through, they will die in time. Many species of insects will probably survive. Life deep in the ocean will probably survive.

 

Buildings should survive. The damage in nuclear explosions is caused by blast force and heat, both of which are missing in any radiation from space so the whole Earth will become like a "ghost town". With most bacteria and such dead, things may not rot away and it will be down to insects to break organic materials down.

[Moontanman]

Gamma rays if sufficient will kill all humans, animals, etc. Animals that live some distance underground may survive longer though with contaminated water soaking through, they will die in time. Many species of insects will probably survive. Life deep in the ocean will probably survive.

 

Um why would the water be contaminated?

 

Buildings should survive. The damage in nuclear explosions is caused by blast force and heat, both of which are missing in any radiation from space so the whole Earth will become like a "ghost town". With most bacteria and such dead, things may not rot away and it will be down to insects to break organic materials down.

 

Why would insects live and bacteria die?

 

A GRB would not have to be extremely close, the burst is along the rotational axis of the star involved, if the pole, either one, is pointed at us then we are in deep trouble, even if it is three times the width of the Milky Way Galaxy away from us...

 

http://en.wikipedia.org/wiki/Gamma-ray_burst

 

Rates and potential effects on life on Earth

 

All the bursts astronomers have recorded so far have come from distant galaxies and have been harmless to Earth, but if one occurred within our galaxy and were aimed straight at us, the effects could be devastating. Currently orbiting satellites detect an average of about one gamma-ray burst per day.

Measuring the exact rate is difficult, but for a galaxy of approximately the same size as the Milky Way, the expected rate (for long GRBs) is about one burst every 100,000 to 1,000,000 years. Only a small percentage of these would be beamed towards Earth. Estimates of rates of short GRBs are even more uncertain because of the unknown degree of collimation, but are probably comparable.

Gamma-ray bursts are thought to emerge mainly from the poles of a collapsing star. This creates two, oppositely shining beams of radiation shaped like narrow cones. Planets not lying in these cones would be comparatively safe; the chief worry is for those that do. [80]

[edit]Potential effect in relation to Deinococcus radiodurans

The first impact is a flash of gamma rays. The flash can damage even the most radiation resistant organism known, the bacterium Deinococcus radiodurans. These bacteria can endure 2,000 times more radiation than can humans.

For a planet with a thin atmosphere, the gamma flash could kill 90 percent of D.radiodurans from distances up to three times our galaxy’s width. A thick atmosphere would protect the microbes from this, but not necessarily from a second component of the beam, ultraviolet radiation.[81]

For thick atmosphere planets, a gamma-ray burst’s ultraviolet rays would kill 90 percent of D. radiodurans at distances ranging from 13,000 to 62,000 light years.

Life surviving that onslaught would have to contend with a third effect, depletion of the atmosphere’s protective ozone layer by the burst. This would kill 90 percent of D. radiodurans at up to 40 percent of the distance across the Milky Way.[82]

[edit]Hypothetical effects of gamma-ray bursts in the past

GRBs close enough to affect life in some way might occur once every five million years or so - around a thousand times since life on Earth began.[83]

The major Ordovician-Silurian extinction event of 450 million years ago may have been caused by a GRB. The late Ordovician species of trilobite that spent some of its life in the plankton layer near the ocean surface was much harder hit than deep-water dwellers, which tended to stay put within quite restricted areas. Usually it is the more widely spread species that fare better in extinction, and hence this unusual pattern could be explained by a GRB, which would probably devastate creatures living on land and near the ocean surface, but leave deep-sea creatures relatively unharmed.[84][85]

[edit]Hypothetical effects of gamma-ray bursts in future

The real danger comes from Wolf–Rayet stars regarded by astronomers as ticking bombs.[86] When such stars transition to supernovas, they may emit intense beams of gamma rays, and if Earth were to lie in the beam zone, devastating effects may occur. Gamma rays would not penetrate Earth's atmosphere to directly impact the surface, but they would chemically damage the stratosphere.

For example, if WR 104 were to hit Earth with a burst of 10 seconds duration, its gamma rays could deplete about 25 percent of the world's ozone layer. It would create mass extinction, food chain depletion and starvation. The side of Earth facing the GRB would receive potentially lethal radiation exposure, which can cause radiation sickness in the short term, and in the long term result in serious impacts to life through ozone layer depletion.[84]

 

Not very likely but....

[maddog]

I see. Someone on a different forum told me that such a weak blast of gamma rays should be considered about the same as x-rays when it comes to inanimate objects. So a concrete building wouldn't be blown away, to be concrete (pun definitely intended).

 

So what you're saying is that the lack of ozone would be balanced out by the increase in heat from the now unhindered sunrays?

An oversimplification. Maybe I wasn't be clear enough.

 

"Weak" blast of Gamma Rays to be is undefined (as in how weak). Depending on frequency Gamma Rays have a bit more energy than X-Rays. Interesting effect occur with Gamma Rays as they hit the upper atmosphere is as collision occurs with atoms in this tenuous upper atmosphere (exosphere) that create exotic decaying particles that are cosmic rays. Many such as Muons, Mesons, etc can be created in these collisions which decay into other particles, etc.

 

So as the intensity were to be increased, this could be devastating effects. Even a nearby star going nova or supernova would not create these more extreme effects. It is the typical "death ray" scenario popularized by early 20th-century sci fi that I am addressing. Say imagine if Gamma Rays could be made to behave coherently. Then a device such as a Gamma Ray Laser (GRL) could be made that at a frequency of say 10^19 GeV in energy could obliterate the Earth. Typical alien invasion sci fi. Then it would matter what was on the other side. It would be gone too.

 

The more mundane things like we really deal with would not be so dramatically devastating.

 

I hope this helps. :rolleyes:

 

maddog

[maddog]

Um why would the water be contaminated?

Not sure actually. One guess might be the proliferation of decay products I spoke of in my last post.

 

Why would insects live and bacteria die?

I personally believe this might be guess on his part. Both would be mutated severely. Maybe because of complexity issues

insects might be more affected. Though this might be a "stretch". Definitely this might be beyond my scope of knowledge, I follow

biology and genetics as I am interested in it. Neither were my major though.

 

A GRB would not have to be extremely close, the burst is along the rotational axis of the star involved, if the pole, either one, is pointed at us then we are in deep trouble, even if it is three times the width of the Milky Way Galaxy away from us...

 

http://en.wikipedia....Gamma-ray_burst

 

Not very likely but....

Well I don't think my example was in this case. A GRB along the axis of rotation of a star going supernova are more likely to be partially

coherent thus like my GRL example. Second even if not the intensity would be higher. The radiation does fall off 1/r^2 though.

So a GRB in our galaxy would definitely be more devastating than say from the Andromeda galaxy a couple of million LY away or one from

say the Virgo Cluster at 60 M-LY away.

 

maddog

[Moontanman]

Not sure actually. One guess might be the proliferation of decay products I spoke of in my last post.

 

EM radiation does not make other things radioactive...

 

I personally believe this might be guess on his part. Both would be mutated severely. Maybe because of complexity issues

insects might be more affected. Though this might be a "stretch". Definitely this might be beyond my scope of knowledge, I follow

biology and genetics as I am interested in it. Neither were my major though.

 

It would depend on how close the GRB was and if the rotational pole was pointed at us. But insects are not necessarily more radiation resistant than bacteria. The link stated that the most radiation resistant organism known would be 90% wiped out if the GRB was three times the width of the Milky Way Galaxy away.

 

Well I don't think my example was in this case. A GRB along the axis of rotation of a star going supernova are more likely to be partially

coherent thus like my GRL example. Second even if not the intensity would be higher. The radiation does fall off 1/r^2 though.

So a GRB in our galaxy would definitely be more devastating than say from the Andromeda galaxy a couple of million LY away or one from

say the Virgo Cluster at 60 M-LY away.

 

maddog

 

If you had read my link you would have seen that the distance does matter, are you claiming the link said it did not?

[Borealis]

Here's an interesting addition:

Let's say the supernova is coming from a rogue star that has passed us at a safe distance, but somewhere on its journey it became entangled with a binary star. Wouldn't that be able to create this exact horror-scenario?

[maddog]

EM radiation does not make other things radioactive...

I didn't think I was implying that. Though GRB when hitting the Earth are thought to be the source of Cosmic Rays.

 

If you had read my link you would have seen that the distance does matter, are you claiming the link said it did not?

I went and read your link to wiki for a second time to be sure. I was demonstrating how distance did matter (or at least I thought I was).

It said on the wiki page you linked to that in our galaxy the possible source of such GRB could come from Magna Stars and

depending on orientation could produce an extinction event. I guess this is what you were alluding to. This is also newer info than

I was aware of. I am seeing my knowledge base being eclipsed because I finding it difficult keeping up with everything. :(

 

maddog

[maddog]

Here's an interesting addition:

Let's say the supernova is coming from a rogue star that has passed us at a safe distance, but somewhere on its journey it became entangled with a binary star. Wouldn't that be able to create this exact horror-scenario?

In what way ? "Engtangled" with ??? If a star were to supernova you would definitely see it. So if a star were to become a binary with another star they both orbit each other about a common center of mass.

 

Please explain. <_<

 

maddog

[CraigD]

Greetings, good people!

The topic is, as you've probably already seen, gamma ray bursts. If we imagine that a moderately powerful burst hit the Earth, killing most humans (but not all) ...

Power (energy/time), or more precisely power flux (power/area) is less important in the total Earth environment impact of a GRB than is its total energy (power x time). There are 2 kinds of GRBs, short, which average less than 1 second in duration, and long, which average about 30. Even a GRB of such duration to occur near Earth and its usually tightly focused (as is believed to be the case with long GRBs) beam strike the Earth, the total energy, and thus damage to the atmosphere and surface/near surface life, would, I think, be survivable, though disease rates, especially skin cancers, might be dramatically increased, much as blood and other cancer rates increased among survivors of the Hiroshima and Nagasaki nuclear bombings.

 

The most deadly effects of the Earth being struck by the beam of nearby average-duration long GRB would, I think, be due to the long-term effects of killing beneficial microorganisms and insects near the surface, and destruction of atmospheric ozone. The hemisphere struck by the gamma and lower-energy ultra-violet light of the GRB would likely lose most of its food crops, resulting in an immediate famine, while, due to ozone loss, it would be difficult to grow crops anywhere in the open for decades to come. With careful management of seeds and the use of UV-protecting covers, world-wide agriculture could be restored, but not, I think, enough and quickly enough to continue to feed everyone, so famine, a terrible die-off, and the breakdown of civilization these historically cause, would occur.

 

Gamma and UV rays are effectively blocked by large thicknesses of water, dirt, concrete, or nearly any material, so the Earth’s ecosystem wouldn’t be “sterilized”. People in the lowest floors of multi-story concrete buildings directly beneath the burst would fare better than people in the open or in thin-roofed buildings or with the burst lower toward the horizon.

 

A longer than average GRB would be worse than a shorter one. Astronomers have detected one GRB that was much longer than average, about 75 days, though to be due to a galaxy’s central supermassive black hole essentially becoming active again. Were this to occur with our Milky Way galaxy, and one of its jets point toward Earth, it would be much worse. I’ve read some speculation that such may actually occur with regularity – it’s one of the possible resolutions for the Fermi paradox, proposing that every few 100,000,000 years of so, all surface life on a wide swath of planets in the galaxy is exterminated, preventing the appearance of intelligent life from being more common than it is. (for more, see Did a gamma-ray burst initiate the late Ordovician mass extinction?, from the reference list of the wikipedia article Fermi paradox)

 

... and severely damaging the ozone layer, what would happen to human-made objects? Would gamma radiation destroy buildings, or leave them unharmed?

 

I think we can safely assume that a burst would set off a chain of fires and explosions in electric systems, but would materials like wood and brick be damaged at all by the blast itself?

Like all photons, and unlike charged particle such as those emitted in solar storms, gamma ray photons are uncharged, so don’t induce potentially damaging currents in electric systems. As with any disaster that disrupts the normal function of civilization, a deadly GRB might lead to various system failures and wide-spread fires, but the direct cause of these would be human activity or negligence.

 

As with most astronomical radiation sources, gamma rays carry only a small amount of the total energy of a GRB. Gamma rays are not dangerous for the amount of energy they deliver, but because the individual photons are so energetic they ionize many of the atoms with which they interact. Too much ionizing radiation is deadly to living organisms. Wood, brick, dirt and water, can be damaged only by large amount of energy, such as very intense light sources (lasers, etc), wrecking balls, bombs, hurricane wind and rain, etc., so I expect they’d survive even the worst of GRBs.

 

I don’t know how a widespread die-off of insects and microorganisms would affect trees, grass, and other vegetation. If it caused widespread die-offs, then terrible continent-wide wild-fires might ensue, dramatically altering the natural and human landscape.

 

Someone on a different forum told me that such a weak blast of gamma rays should be considered about the same as x-rays when it comes to inanimate objects.

That’s correct.

The x-ray band of the EM spectrum is conventionally defined as frequencies from 3 x 10¹⁶ to 3 x 10¹⁹ hz, gamma rays as 10¹⁹ and greater, so the bands actually overlap slightly.

 

Almost all nuclear reactions, the most common source of gamma rays, emit no EMR above 10²¹ hz. GRBs can emit even high-frequency EMR, which for lack of a better term is still called gamma, but as these pass through most biological material with little interaction, they’re not a significant concern for this thread’s subject.

 

Here's an interesting addition:

Let's say the supernova is coming from a rogue star that has passed us at a safe distance, but somewhere on its journey it became entangled with a binary star. Wouldn't that be able to create this exact horror-scenario?

According to best understanding of how GRBs happen (which is still far from perfect) No.

 

To get a star-generated GRB, you’ve got to have the collapse of a large, aged star into a ultra-compact remnant such as black hole or neutron star. To get a supper-massive black hole-generate one, you’ve got to have ... well, a super-massive black hole, and something massive to collide with it, like a star, neutron star, stellar-mass black hole, or a vast dust and gas cloud. Crashing together or otherwise “entangling” any number of stars other that aren’t near exhausting their fuel and collapsing won’t make a GRB.

 

If you have a stellar-mass BH, however, hitting it with enough matter could produce a GRB, so the collision of a black hole with its partner in a binary system is a reasonable candidate for a GRB source. In principle, colliding a stellar-mass BH with a star from anywhere might produce a GRB, but stars being small compared to the space between them, this seems unlikely. Getting a star that didn’t form along with another to orbit it is hard to imagine, also, because such orbital insertion maneuvers require lots of non-gravitational acceleration, and it’s hard to imagine how to accelerate a star.

 

I think a BH passing through a dense dust/gas cloud might produce a GRB, though I’ve never read of any speculation about or possible observation of such a thing, so may be wrong.