Gamma Radiation Bursts (GRB) and the danger to life on Earth
Not sure if any of you are aware of what gamma radiation bursts are but there is some speculation that at least one or more of the massive die offs of Earth creatures in Earth's past may have been connected to such a thing.
I'll post some articles later.
To summarize, a GRB occurs (we think) when a nova or supernova occurs, a star collapses, two massive bodies collide (likely black holes) or possibly local to our own area of space, the sun spits out a massive coronal mass ejection which hits the planet.
May 15th, 2013, 15:13
American Patriot
Re: Gamma Radiation Bursts (GRB) and the danger to life on Earth
http://timeecocentric.files.wordpres...0&h=240&crop=1 NASA / P. Cowperthwaite / University of Maryland A still from a computer simulation showing two black holes merging. Climate scientists consult ancient tree rings all the time. These year-by-year growth bands, preserved in long-lived timber, can reveal how warm and how wet the planet was many centuries before thermometers or rain gauges were invented. For astronomers, by contrast, the idea of studying the stars by drilling into tree trunks would seem absurd. (RD: Which is why scientists NEED to work together. Global warming is absolute bullshit, because things come from outerspace all the time and cause all kinds of problems on the planet, having NOTHING whatsoever to do with human habitation)
Or maybe not. Sometime between the spring of 774 A.D and the summer of 775, a cataclysmic event happened somewhere out in the cosmos — and we felt it here, as a spike of radioactive carbon-14 and beryllium-10. The isotopes were taken up by growing Japanese cedar trees and there they remained.
The tree rings were flagged last summer in a paper written by Japanese physicist Fusa Miyake, of Nagoya University. Ordinary cosmic rays — atomic nuclei and subatomic particles that speed through the Milky Way — create carbon-14 in the upper atmosphere all the time, but at a more or less steady rate. What caught Miyake’s eye was that in this one window in history, during the late eighth century, the level was roughly 20 times higher.
When Ralph Neuhauser, of the University of Jena, in Germany, and his collaborator read the report, they immediately began speculating about the cause and in a paper just published in Monthly Notices of the Royal Astronomical Society, they have come up with an answer: a violent collision between the dense, compact remains of two dead stars — two black holes, perhaps, or a pair of neutron stars. That conclusion, however, required them to consider a number of other possibilities first, including one of the most obvious: a supernova — an idea they quickly rejected.
“If it were a supernova,” says Neuhauser, “you can calculate from the amount of carbon-14 how far away it would have been.” The answer: between 400 and 1,000 light-years. But a star exploding that close by would undoubtedly have been seen and noted at the time, he says, and even if it weren’t, the nebula of glowing gas left behind would long since have been spotted by modern telescopes. Or it could have been an unusually powerful solar flare or coronal mass ejection — but that, too, would probably have been noticed thanks to the overwhelmingly bright auroras it would have triggered in Medieval night skies.
So Neuhauser and University of Jena co-author Valeri Hambaryan turned to another possibility: the very short gamma-ray blasts triggered when two super-dense objects collide. Such collisions don’t produce a flash of visible light, so you wouldn’t expect to find any records even if someone had been looking in the right direction during that fateful two seconds.
(More: The Super-Duper Planet-Frying Exploding Star That’s Not Going to Hurt Us, So Please Stop Worrying About It)
What such collisions do produce, however, is an enormous burst of gamma rays in less than two seconds. And when those speeding waves of electromagnetic energy reached Earth, they would have zapped nitrogen atoms in the upper atmosphere, transforming them into just the storm of radioactive carbon and beryllium that was captured by the trees.
If such a collision had happened within 3,000 light-years of Earth, the blast of gamma rays would have been powerful enough to reach right down to the planet’s surface, and it would have been lethal enough to wipe out many species. Since no such mass extinction happened, reason Neuhauser and Hambarayan, the gamma bath must have come from farther away, but still less than 12,000 light years, judging by how much carbon-14 did get preserved.
And exactly where in the sky did the collision occur? That’s much tougher to figure out. Winds spread carbon-14 through Earth’s atmosphere within a few months, so the effect would have been world-wide — meaning that it’s not so easy as looking just in the northern sky that would have been visible from Japan. Nevertheless, says Neuhauser, it’s possible that trees would have slightly more of the element in the hemisphere where the blast first struck. If by chance the triggering event had been a solar flare after all, you’d expect to find more carbon-14 near the poles, where Earth’s magnetic field would have channeled particles from the Sun.
The good news, says Neuhauser, is that this single event is the only one of its kind in the past 3,000 years, which is as far back in time as tree rings reliably go. Black holes and neutron stars can be tough to spot, and if our corner of the Milky Way were packed with either kind of cosmic oddball,we might have to worry about gamma-ray showers as a significant threat. The trees tell us a dramatic — but also reassuring — tale.
http://timeecocentric.files.wordpres...0&h=240&crop=1 Marco Lorenzi / Getty Image Remember Mr. Creosote? If you don’t, he’s worth getting to know — but only if you have a very strong stomach. Mr. Creosote was the colossally obese character in Monty Python’s Meaning of Life who gorged himself on buckets of food in a French restaurant, somehow surviving his own gluttony, but only until he capped off the meal with a single “waffer-thin mint.” Then he, um, exploded. Well, Mr. Creosote, meet the Type 1a supernova. You two characters have a lot in common.
Supernovas come in more than just one flavor. The most common variety occurs when a star has exhausted all or most of its hydrogen fuel and its decaying core suddenly collapses, generating a burst of gravitational energy that triggers a massive explosion — one that may briefly appear brighter than an entire galaxy. A somewhat more complex dynamic plays out in what’s known as a Type 1a supernova, which is the eruption of a small, dead carcass of a star known as a white dwarf. In general, white dwarfs don’t have sufficient mass to trigger supernovas, but if they’re part of a binary system with a nearby red giant, the dwarf may suck in enough matter from its much bigger sibling that it eventually blows. The waffer-thin mint on a cosmic scale.
Type 1a supernovas are rare — typically there are only one or two per century in an average-size galaxy. More common are smaller, garden-variety white-dwarf explosions — novas without the super prefix — sometimes occurring repeatedly as a single white dwarf vacuums up and blasts away red giant material over and over again. The Milky Way itself is home to a recurrent nova called RS Ophiuchi, which is located 5,000 light-years from Earth and erupts roughly once every 20 years. What has never been seen is a recurring nova that eventually reaches the super level. The mere fact of shedding matter in the smaller bursts prevents it from ever attaining the mass for a truly big blow.
Or at least that was always the thinking. But a paper published in the Aug. 24 issue of Science provides evidence of the first ever recurring nova that did go super. The method used to detect the phenomenon is almost as impressive as the fact that it happened at all.
The exploding star, known as PTF 11kx, is found in the constellation Lynx, 600 million light-years from Earth. It was detected on Jan. 16, 2011, by the Palomar Observatory in California. The light signature pouring into the 48-in. telescope that night was unmistakably that of a supernova, and shortly after its detection, Peter Nugent, a senior scientist at the Lawrence Berkeley National Laboratory, and Jeffrey Silverman, a postdoctoral student at the University of California, Berkeley, began taking spectroscopic measurements of the expanding cloud of gas and other matter, trying to learn more about its chemical signature. They found a great deal of calcium mixed in with the other elements — and that surprised them.
Calcium is a common byproduct of stellar detonations, but this expanding shell of the material was too far away from the freshly exploded star and moving too slowly to be the result of the supernova that had just occurred. It would be easy enough to explain the calcium’s presence if the star had gone nova once before, releasing a burst of the element in all directions and then slowing steadily as it encountered the stellar wind that permeates space. But that would mean that the elusive recurrent nova that goes super would finally have been found. The only way to determine if this was so would be to watch. If the calcium signal faded and slowed further and then lit up explosively when the fresh blast of faster star debris caught up with it and energized it, the deal would be sealed. Exactly 58 days later, that’s what happened.
“This was the most exciting supernova I’ve ever studied,” postdoctoral researcher Ben Dilday of the University of California at Santa Barbara, who was the lead author of the Science paper, said in a statement. “For several months, almost every new observation showed something we’d never seen before.”
It’s not clear how common recurrent Type 1a novas that eventually go supernova are, th0ugh Silverman suspects that the mere fact that astronomers have been studying novas for so long and never seen one like this before is a sign that they’re pretty rare. It’s not even clear whether many folks outside the astronomy community will care terribly much that a sub-subcategory of the familiar supernova has at last been identified. But the astronomers care deeply, and well they might. Cosmic phenomena do a very good job of concealing themselves from us. Every curtain we part makes the universe a more transparent — and, in this case, literally more dazzling — place.
More than 90 percent of all organisms that have ever lived on Earth are extinct. As new species evolve to fit ever changing ecological niches, older species fade away. But the rate of extinction is far from constant. At least a handful of times in the last 500 million years, 50 to more than 90 percent of all species on Earth have disappeared in a geological blink of the eye.
Though these mass extinctions are deadly events, they open up the planet for new life-forms to emerge. Dinosaurs appeared after one of the biggest mass extinction events on Earth, the Permian-Triassic extinction about 250 million years ago. The most studied mass extinction, between the Cretaceous and Paleogene periods about 65 million years ago, killed off the dinosaurs and made room for mammals to rapidly diversify and evolve.
The causes of these mass extinction events are unsolved mysteries, though volcanic eruptions and the impacts of large asteroids or comets are prime suspects in many of the cases. Both would eject tons of debris into the atmosphere, darkening the skies for at least months on end. Starved of sunlight, plants and plant-eating creatures would quickly die. Space rocks and volcanoes could also unleash toxic and heat-trapping gases that—once the dust settled—enable runaway global warming.
An extraterrestrial impact is most closely linked to the Cretaceous extinction event. A huge crater off Mexico's Yucatán Peninsula is dated to about 65 million years ago, coinciding with the extinction. Global warming fueled by volcanic eruptions at the Deccan Flats in India may also have aggravated the event. Whatever the cause, dinosaurs, as well as about half of all species on the planet, went extinct.
Massive floods of lava erupting from the central Atlantic magmatic province about 200 million years ago may explain the Triassic-Jurassic extinction. About 20 percent of all marine families went extinct, as well as most mammal-like creatures, many large amphibians, and all non-dinosaur archosaurs. An asteroid impact is another possible cause of the extinction, though a telltale crater has yet to be found.
Largest Ever Die-Off
The Permian-Triassic extinction event about 250 million years ago was the deadliest: More than 90 percent of all species perished. Many scientists believe an asteroid or comet triggered the massive die-off, but, again, no crater has been found. Another strong contender is flood volcanism from the Siberian Traps, a large igneous province in Russia. Impact-triggered volcanism is yet another possibility.
Starting about 360 million years ago, a drawn-out event eliminated about 70 percent of all marine species from Earth over a span of perhaps 20 million years. Pulses, each lasting 100,000 to 300,000 years, are noted within the larger late Devonian extinction. Insects, plants, and the first proto-amphibians were on land by then, though the extinctions dealt landlubbers a severe setback.
The Ordovician-Silurian extinction, about 440 million years ago, involved massive glaciations that locked up much of the world's water as ice and caused sea levels to drop precipitously. The event took its hardest toll on marine organisms such as shelled brachiopods, eel-like conodonts, and the trilobites.
Happening Now?
Today, many scientists think the evidence indicates a sixth mass extinction is under way. The blame for this one, perhaps the fastest in Earth's history, falls firmly on the shoulders of humans. By the year 2100, human activities such as pollution, land clearing, and overfishing may have driven more than half of the world's marine and land species to extinction.(RD: Ummm. Not. Most of the "mass die offs" came quickly. The records show they happened over the course of less than a 100 years in many cases, I'll have to find and post that evidence when I have time).
May 15th, 2013, 15:20
American Patriot
Re: Gamma Radiation Bursts (GRB) and the danger to life on Earth
It has been hypothesized that a gamma-ray burst in the Milky Way, pointing directly towards the Earth, could cause a mass extinction event.Melott, A.L. et al. (2004). "Did a gamma-ray burst initiate the late Ordovician mass extinction?". International Journal of Astrobiology 3: 55–61. arXiv:astro-ph/0309415. Bibcode:2004IJAsB...3...55M. doi:10.1017/S1473550404001910.
May 15th, 2013, 15:22
American Patriot
Re: Gamma Radiation Bursts (GRB) and the danger to life on Earth
The above figure illustrates the locations of 2512 gamma-ray bursts detected by the BATSE instrument after more than eight years of observation.
Statistical tests confirm that the bursts are isotropically distributed on the sky - no significant quadrupole moment or dipole moment is found. At the same time, a deficiency has been detected in the number of faint bursts, interpreted as an indication that the spatial extent of the burst distribution is limited and that BATSE sees the limit or edge of the distribution. The nature of the sources remains unknown. However, their isotropic distribution on the sky along with the deficiency of faint bursts can be naturally explained if the bursts are located at cosmological distances (far beyond the Milky Way). This interpretation has been confirmed in recent years via distance estimates for optical counterparts to gamma-ray bursts.
May 15th, 2013, 15:24
American Patriot
Re: Gamma Radiation Bursts (GRB) and the danger to 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. The closest known GRB so far was GRB 031203.[85]
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.[86] 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.[87]
Depending on distance, a gamma flash and its ultraviolet radiation could damage even the most radiation resistant organism known, the bacterium Deinococcus radiodurans. These bacteria can endure 2,000 times more radiation than humans. Life surviving an initial onslaught would have to contend with a potentially lethal aftereffect, depletion of the atmosphere's protective ozone layer by the burst.[88]
May 15th, 2013, 15:25
American Patriot
Re: Gamma Radiation Bursts (GRB) and the danger to life on Earth
Nobody knows exactly what triggers lightning bolts. Now, two Russian researchers say these discharges of a billion volts or more could be caused by the interaction of cosmic rays – high-energy particles from outer space – with water droplets in thunderclouds.
Cosmic rays are created deep in space by powerful events such as star collisions, gamma ray bursts and supernovae. These cataclysms accelerate charged particles, mostly protons, to very high energies. The rays zoom across space, and those that strike the upper atmosphere of Earth generate invisible but highly energetic air showers of ionized particles and electromagnetic radiation.
The idea that these air showers could cause lightning when they pass through a thundercloud has been around for two decades. Russian physicist Alexandr Gurevich suggested that the high-energy particles produced by a cosmic ray strike ionize the air in thunderclouds, creating a region with a lot of free electrons.
The thundercloud’s electric field accelerates the electrons almost to the speed of light, boosting them to very high energies. Then the electrons collide with atoms in the air, generating even more electrons as well as X-rays and gamma rays. This avalanche of high-energy particles in the cloud – which Gurevich calls “runaway breakdown” – provides ideal conducting conditions for lightning.
Researchers have debated Gurevich’s idea ever since, says Joseph Dwyer, a lightning scientist at the Florida Institute of Technology, who was not involved in the study. But Gurevich hasn’t found concrete evidence that cosmic rays are the culprits.
Radio waves could provide a clue, Dwyer says: Cascades of electrons at the onset of a lightning strike should produce radio waves. “The cosmic ray community has known that cosmic rays make radio waves, and when there are thunderstorms around, it’s been seen that you get more of these radio pulses,” Dwyer says. “But no one has yet closed the loop and really shown that the air showers going through (a thundercloud’s) electric field making these runaway electrons are the things that are doing it.”
To test the concept, Gurevich and his colleague Anatoly Karashtin analyzed data from 3,800 cloud-to-ground lightning strikes recorded in Russia and Kazakhstan. The results, reported this month in Physical Review Letters, show that storm clouds emit “hundreds or thousands” of short, strong radio pulses just before lightning strikes. Their shape, the researchers say, matches their models of runaway breakdown triggered by energetic cosmic rays. But there’s a problem: Cosmic rays with enough energy are too rare to trigger all the pulses that Gurevich and Karashtin observed.
So-called hydrometeors – hail and water droplets in each cloud – may be amplifying the pulses, Gurevich and Karashtin propose, and trigger a flurry of microdischarges that boost both the current and the radio pulse signal.
But British lightning scientist Clive Saunders remains unconvinced. “They have not shown a correlation between lightning activity and the rate of arrival of cosmic rays at the Earth,” he said.
