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Several studies in the past have demonstrated how longer high-energy radiation bursts, such as those caused by supernovae, and extreme solar flares can deplete stratospheric ozone, allowing the most powerful and damaging forms of ultraviolet radiation to penetrate to the Earth’s surface. The probability of an event intense enough to disrupt life on the land or in the oceans becomes large, if considered on geological timescales.
So getting a handle on the rates and intensities of such events is important for efforts to connect them to extinctions in the fossil record. “We find that a kind of gamma ray burst — a short gamma ray burst — is probably more significant than a longer gamma ray burst,” said astrophysicist Brian Thomas of Washburn University. Improved and accumulated data collected by the SWIFT satellite, which catches gamma ray bursts in action in other galaxies, is providing a better case for the power and threat of the short bursts to life on Earth.
“The duration is not as important as the amount of radiation,” said Thomas. If such a burst were to happen inside the Milky Way, it its effects would be much longer lasting to Earth’s surface and oceans. “What I focused on was the longer term effects,” said Thomas.
The first effect is to deplete the ozone layer by knocking free oxygen and nitrogen atoms so they can recombine into ozone-destroying nitrous oxides. These long-lived molecules keep destroying ozone until they rain out. “So we see a big impact on the ozone layer.” Those effects are likely to have been devastating for many forms of life on the surface — including terrestrial and marine plants which are the foundation of the food web.
This challenges notions of how these powerful electromagnetic rays - like light, but far more energetic - are formed, researchers suggest in Science.
They found emissions at more than 100 gigaelectronvolts - 100 billion times more energetic than visible light.
"These are much, much higher energies than had been previously thought can come from a pulsar," Dr Otte said.
"It's a very radical change to the picture of how we believe gamma-ray emission comes from pulsars," he said.
Originally posted by sostoned
This is an article you might find interesting which explains the cosmic events in relation to our solar system's position in the galaxy. Nice post. www.dailygalaxy.com... g/2010/08/the-milky-way-orbit-biodiversity-link-a-galaxy-most-popular.html
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays (especially in astronomy, by analogy with X-rays) and denoted as γ, is electromagnetic radiation of high frequency (very short wavelength). Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei (gamma decay). Important natural sources are also high-energy sub-atomic particle interactions resulting from cosmic rays. Such high-energy reactions are also the common artificial source of gamma rays.
Other man-made mechanisms include electron-positron annihilation, neutral pion decay, fusion, and induced fission. Some rare natural sources are lightning strike and terrestrial gamma-ray flashes, which produce high energy particles from natural high-energy voltages. Gamma rays are also produced by astronomical processes in which very high-energy electrons are produced. Such electrons produce secondary gamma rays by the mechanisms of bremsstrahlung, inverse Compton scattering and synchrotron radiation. Gamma rays are ionizing radiation and are thus biologically hazardous.
"Astronauts in space are exposed to radiation, and this can damage their DNA," explains Frank Cucinotta of NASA's Space Radiation Health Program. Of particular concern are heavy cosmic rays--the energetic nuclei of iron atoms, for instance--which can crash through DNA like little atomic cannonballs, causing complex breaks called "clustered DNA damage."