“Life Extinctions by Cosmic Ray Jets”, by Arnon Dar, Ari Loar, and Nir Shavi
http://arxiv.org/PS_cache/astro-ph/p.../9705008v1.pdf
In reply to neilzero and m1omg’s comments
It looks like the gamma ray pulse which damages the ozone layer is a serious problem, however, because it is short 10 seconds and only half of the earth is exposed to the burst, there are fairly simple methods to mitigate the loss of life. My comments above - Suggesting the use of electric powered greenhouses - were to adjust to the damage to the ozone layer and to the abrupt cooling of planet. It appears however there is another more serious problem.
The above paper explains the other problem associated with a gamma burst which is the accompanying burst of high energy baryons. This problem needs additional formal research. The high energy burst of baryons, if it struck the planet on or near the equator (i.e. The entire planet’s surface is expose to the high energy baryons.) would have significant consequences, assuming the calculations in above paper are correct.
If further formal analysis indicates there was a real possibility this type of event does happen and that WR104 could and could likely cause that type of event, something like a moon based human colony or probably more practical multiple very deep earth based human colonies would be required, to re-populate the earth with most life forms, a half dozen years after the event, based the above authors' analysis.
The following is an excerpt from the above paper:
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Unattenuated jets from neutron stars to neutron star mergers (my comment: Supernova collimate jets are now hypothesized to be the source of Gamma Ray Bursts and Cosmic Rays, see papers linked above.) can be devastating to life on nearby planets: At a distance of 1 kpc their duration is ∼ 1 day − 2 months ….Thus, the energy deposition in the atmosphere by the jet is equivalent to the total energy deposition of galactic cosmic rays in the atmosphere over ∼ 10^7 y. However, the typical energy of the cosmic rays in the CRJ is ∼ 1 T eV per nucleon, compared with ∼ 1 GeV per nucleon for ordinary cosmic ray nuclei. Collisions of such particles in the atmosphere generate atmospheric cascades where a significant fraction of the CRJ energy is converted into “atmospheric muons” through leptonic decay modes of the produced mesons. Most of these muons do not decay in the atmosphere because of their high energy, unlike most of the atmospheric muons which are produced by ordinary cosmic rays. The average number of high energy muons produced by nucleons of primary energy Ep, which do not decay in the atmosphere and reach sea level with energy > Eμ at zenith angle ….Such muons deposit energy in matter via ionization. Their energy deposition rate is …The whole-body lethal dose from penetrating ionizing radiation resulting in 50% mortality of human beings in 30 days [26] is ≤ 300 rad ∼ 2×10^10/(dE/dx) ∼ 10^10 cm−2 where dE/dx is in rate is in MeV g−1cm−1 units. The lethal dosages for other vertebrates can be a few times larger while for insects they can be as much as a factor 20 larger. Hence, a CRJ at D ∼ 1 kpc which is not significantly dispersed by the galactic magnetic field produces a highly lethal burst of atmospheric muons. Because of muon penetration, the large muon flux is lethal for most species even deep (hundreds of meters) underwater and underground, if the cosmic rays arrive from well above the horizon. Thus, unlike the other suggested extraterrestrial extinction mechanisms, a CRJ which produces a lethal burst of atmospheric muons can explain also the massive extinction deep underwater and why extinction is higher in shallow waters.
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Although half of the planet is in the shade of the CRJ, planet rotation exposes a larger fraction of the planet surface to the CRJ. Additional effects increase the lethality of the CRJ over the whole planet.
They include:
(a) The pollution of the environment by radioactive nuclei, produced by spallation of atmospheric and surface nuclei by shower particles. …Global winds spread radioactive gases in a relatively short time over the whole planet.
(b) Depletion of stratospheric ozone by the reaction of ozone with nitric oxide, generated by the cosmic ray produced electrons in the atmosphere (massive destruction of stratospheric ozone has been observed during large solar flares which produced energetic protons [28]).
(c) Extensive damage to the food chain by radioactive pollution and massive extinction of vegetation and living organisms by ionizing radiations (the lethal radiation dosages for trees and plants are slightly higher than those for animals but still less than the flux given by eq. 5 for all except the most resilient species).
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